Need a little help figuring something out

[SSLance]

Just finished up my first autocross weekend of 2013 and once I ironed out all of the kinks and started to get used to my new setup, I noticed one thing in particular that is slowing me down and I'm not sure why my car does this? Not sure if it is something car setup related or something I'm doing inside the car.

I ran my GoPro behind all four tires over the weekend, the back tires on Saturday during the test n tune session and the fronts on my first two runs of Event 1 on Sunday.

Here's the video of all of them.

http://youtu.be/idpMHtBwAm4

At about 1:58 in, you will notice that my right rear tire starts chattering and the rear looses traction. This happened with some regularity all weekend long, and it only does it on left hand turns...the back actually feels real good on right handers. I've got the front sorted out pretty well too, as long as I get it braked and settled before turning it, the front sticks pretty good.

Here's my complete setup as it sits now

Front
DSE upper control arms, DSE 2" drop 575# springs, Edlebrock IAS shocks (5 years old), everything else stock F41 stuff except poly bushings in the sway bar with
245/40/17 Nitto 555s

Rear
9" with Explorer disc brakes, UMI double adjustable UCAs and LCAs with Delrin ends, Hotchkiss 1" solid sway bar attached to LCAs, DSE 2" drop 125# springs Edlebrock IAS shocks (5 years old), 275/40/17 Nitto 555s

Here is the corner weights with me in the car

https://static1.pt-content.com/images/noimg.gif

Here is my current alignment specs

https://static1.pt-content.com/images/noimg.gif

It seems so far like the tires like about 34 psi in the fronts and 30 psi in the rears. Drive train is a carb fed 383 and new this year is a T56.

Here is some in car videos from both days also, I'd appreciate any input you guys have at all. I'm fairly new at this and while not trying to compete directly with all of the Evos and Mazdas out there, I would like to help me and the car run as well as we can without breaking the bank so to speak.

http://youtu.be/hSNg7yTPAr0

Here's a few action shots of the car from the weekend also.

https://static1.pt-content.com/images/pt/2013/04/kcrscca_solo1_040713_072-1.jpg


https://static1.pt-content.com/images/pt/2013/04/kcrscca_solo1_040713_086-1.jpg

[rchaskin]

Preface....this is coming from a total novice.

I would probably replace the shocks to Koni or similar.

The videos looked good. smooth driving.
I would also like to see a more liberal dose of throttle as well. That is just my style.....

PS, it is going to be tough to catch the Evos......That is a well enginered car.

Good Luck.

[marolf101x]

The IAS shocks could be causing some of that. Watch the LR as it goes over the first bump just after the initial right hand turn, you'll notice the tire "bounces" after the bump.
A good set of rebound adjustable units will help:
http://ridetechshocks.com/gm-shocks/gm-g-body/1978-88-g-body/

[SSLance]

I was thinking the symptom I'm experiencing may be shock related, but I don't understand why it would do it on one side but not the other?

I haven't thought about switching the shocks from side to side to see if that changes anything but that may be an idea to try.

See, I'm from Missouri...the Show Me State, plus I'm mechanically inclined enough (but not engineer level by any means) to want to know and understand how something works and why before progressing with it. I have not gone down that path with damping control just yet (although I currently have 8 tabs open to threads here on the subject).

Britt, can you (in laymen's terms) give me a quick explanation as to how adjusting the rebound of a shock will aid in the way my suspension works? In other words what exactly would be different with different settings of rebound vs what I have now with my over the counter shocks?

[SSLance]

While reading a thread here on anti-squat, something else came to me...and made me think maybe two different things are going on here.

I tend to loose the back end coming out of corners under hard acceleration turning left...but not when turning right. Could the drive shaft torque have an effect on this by raising the right rear under acceleration?

Looking at my video again and watching both side's tires after Britt's post made me realize that both of the tires are reacting to bumps in about the same manner, but something is definitely different as I constantly have to watch how much power I put down leaving a left hander vs just hammering down out of a right hander with very different results.

[MrQuick]

I'd like to see a picture of your rear sway bar at ride height. You might be loosing travel due to bind causing you to unload the tire.

[marolf101x]

Shocks are pretty simple if you remember this. . .they are simply timing devices. They determine when things happen and how long they stay there.

Take a really basic example: (we will concentrate on rebound only and on the front only, keeping compression the same. I'll get to more of this later.)
You are going down a straight into a left hand corner that's long and "smooth" (not the track surface, but in radius).
As you approach the turn you apply the brakes, the weight shifts forward onto the front tires (at this point the front tires are doing most of the work). When the speed is acceptable you turn in. As you turn through the corner you want enough weight over the front so the tires keep grip, and enough on the rear so it doesn't break loose. (If you use a trailbraking technique you are effectively holding the weight on the front tires while scrubbing off a little speed allowing you to drive in harder and save time.) As you approach the apex you want the car perpendicular to the apex and the front tires straight (you are basically done turning) so when you pick up the throttle for corner exit the weight begins to shift to the rear tires as they need grip for forward traction. If the car is straight you don't need any weight on the front tires (think drag racing), but in reality the corner force is still pushing the car to the outside of the turn, so you need some weight on the front.

The shock plays a major roll in when the weight is transferred.

If the shock has too little rebound the weight will have transferred to the rear before you hit the apex, and the car will push (understeer) as the front tires are picked up off the pavement (not really picked up, but it gives a better visual).

If the shock has too much rebound it will "hold" the front down too long. In this situation the front will still be "overloaded" as you begin applying throttle and the rear will loose grip (causing oversteer, or just spinning, depending on the position of the car in the turn.)

Now, that does not take into account rear rebound, or compression on any corner. Adjustments to these items will affect the timing.

Compression:
I don't like a lot of compression in a street car. It's the springs job to absorb the impact of a bump, or to help control roll (sway bars have a major impact, but let's keep it simple). Additional compression is like having a very high spring rate. . .any harshness is transferred into the chassis as the force has to go somewhere, and the spring is not dissipating it. High compression forces cause poor ride quality.

The info and examples above are very basic. There's a lot going on in an automotive suspension, and each has a positive and negative effect on all others. As always it's a balancing act.
And remember, no two people have the exact same driving styles, so a "smooth" driver will have a different set up than someone who treats the pedals like a light switch!
The beauty of an adjustable damper is that you can "dial in" just what the driver or car wants or needs.
The downside is that you may have a thousand different setting possibilities, but only a few will work well. Only seat time, test and tune sessions, and reliable advice can overcome this.

[SSLance]

Just took these...


https://static1.pt-content.com/images/pt/2013/04/DSC02736_zps0e6c3c7b-1.jpg

https://static1.pt-content.com/images/pt/2013/04/DSC02735_zps5e9d753f-1.jpg

https://static1.pt-content.com/images/pt/2013/04/DSC02733_zps8bcf38fe-1.jpg

https://static1.pt-content.com/images/pt/2013/04/DSC02734_zps1bf47ce1-1.jpg

[SSLance]

Thanks a LOT Britt, that helps a ton. I actually envisioned what a shock was doing in rebound and compression exactly backwards. You've made it much clearer, thanks.

I have found with my car in it's current setup it runs quicker times if I'm smoother trail braking and under throttle, any abruptness with either pedal causes it to either understeer or oversteer...the more abrupt the worse the loss of traction on both ends. I've found if I left foot brake and modulate pressure between the gas and brake evenly the car stays settled and runs quicker. I'm still new enough that I'm not sure which method I prefer more, I've just learned to do this to make the car work. I'm okay at it I think, but I"m not opposed to being a pedal masher either if it'll work with the car.

Saturday was my first run with the T56 and more power under the hood. It took me 3-4 runs to learn to back off on throttle application enough to keep from breaking the rear tires loose...it was all together different than with the Auto trans. Car would make a helluva drifter setup like it is right now. :D

Now, back to the shocks... It sounds like my front shocks have too much rebound as the front stays down and the back stays up as the car exits a turn.

The rear, I have never liked the shocks as far as street driving. When I pull into my garage, that little 1 inch bump up onto the garage floor is almost jarring...it's so abrupt. Sounds like they have too much compression? Trying to do the work of the springs?

[SSLance]

Speaking of travel, I should explain another part of what I've had to do with the rear. When I put the DSE 2" drop springs in, I had a clearance issue with my caliper bolts and the frame.

I ended up spinning the brake backing plate 180 degrees on each side to get the most clearance I could get. But I still only have about 2.25" of travel before the poly bump stops touch the frame.

https://static1.pt-content.com/images/pt/2013/04/DSC02143-1.jpg

Here is the travel with the spring and bump stop removed

https://static1.pt-content.com/images/pt/2013/04/20120829_185328_443-1.jpg

I haven't seen much evidence of the bumps riding on the frame, but I could shorten them if I thought the frame was getting onto the bumps and upsetting the car.

This is the main reason I did the rear wheel cam shots, I don't think this is and issue after watching the video, do any of you?

[SSLance]

I put the car up on the lift last night and found this...Looks like I've got my work cut out for me before Sunday

Right rear tire rub on frame

https://static1.pt-content.com/images/pt/2013/04/IMG_20130411_180550_681-1.jpg


Exhaust drooped over and hitting pass side upper control arm

https://static1.pt-content.com/images/pt/2013/04/IMG_20130411_181209_447-1.jpg



Upper control arm frame end driver side delrin joint

https://static1.pt-content.com/images/pt/2013/04/IMG_20130411_180903_672-1.jpg


The right tire has never rubbed the frame before, it's a 1/4" closer to the frame than the driver side. I think the 6 psi drop in tire pressure last weekend is what let the tire come over to contact the frame. The Hoosiers I'm running this week are on narrower wheels with less backspace so this won't be an issue with them.

The exhaust hitting the UCA is a symptom of the new X-pipe put on in a hurry after I had to swap the headers due to the T56 swap last December. The tail pipes and mufflers kept rotating in the X pipe so the exhaust shop tack welded it in place, they just forgot to twist the over the axle part back up straight before tacking. I'll cut the tack weld loose and loosen the clamp on the X-pipe and lift on the bottom of the inside of the muffler to rotate things back into place and tack it up again.

And the delrin joint just needs to be loosened, straightened up and tightened again. I'll need to verify the whole thing isn't loose therefore disrupting not only the pinion angle but also might be letting the axle move to the Driver's side.

The bump stops do not appear to be contacting the frame (good thing), the frame was dirty and not wiped clean by contact from the poly stops.

All of these problems are new this year, they were not part of the problem causing the loose condition last year, but I will correct them and put the new tires on and run this Saturday and see what happens.

I'll report back with my findings.

Thanks for your help with this everyone...we'll get it figured out soon.

[David Pozzi]

The corners at 1:58 are grooved concrete. The tires will have less grip there. Plus concrete that is smooth can have high grip, but usually has more sudden breakaway with greater loss of grip once the tire is sliding. Tires don't easily re-grip concrete like they do Asphalt.

[Rick Dorion]

I used the IAS shocks on one of my vehicles years ago and the damping went away within a year or two.

[Mizzouri]

it was good to me you last Sunday Lance. I am definitely looking forward to round 2 as the weather looks to be oh so nice.

[SSLance]

I had fun last weekend as well, what car were you in? (I remember more people by their car than in person).

I hope it warms up, I'm ready for spring to get here and stay this time.

[4WardInv]

Not to take anything away from all the other info here but first thing I would do is square up the rear end. Your thrust angle is at .06 which probably doesn't seem like much but that's enough to make a new Volvo Semi have a pull. The rear is pointed to the right so right hand turns are going to feel better than left. Try to get it as close to zero as possible.

[SSLance]

Well, that was my intention with the new double adjustable control arms but the guys at the alignment shop said that that was pretty damn close and wouldn't make a big difference trying to get it closer to 0.00.

If the fixes I've made don't cure it that will be my next move.

Both jam nuts were loose on driver's UCA and it was about a 1/4" shorter than the other, hence the tire rub. Fixed...

That is the second time those jam nuts have come loose, gonna have to keep a closer eye on them.

The tack weld on the exhaust joint behind the X-pipe broke and the clamp was loose, so the tailpipe rotated over into the UCA. I notched the female end of the X-pipe, re-installed pipe and clamped it down tight. Should have fixed that right the first time, now it's fixed though.

Got my ZQ8 wheels with the Hoosier A6s on them mounted up and test drove and that all seems fine.

https://static1.pt-content.com/images/pt/2013/04/IMG_20130413_094544_589-1.jpg

https://static1.pt-content.com/images/pt/2013/04/IMG_20130413_094024_606-1.jpg

I think I'm all set for Event #2 tomorrow, just have to load everything up.

I'll report back with the results. Thanks for the help everyone.

[4WardInv]

Good luck and have fun with it tomorrow !

I hate when guys at alignment shops don't do a complete job, you can tell them I work for Hunter Engineering (the company that built the machine they're using) and I think they cheated you!

By the way my names also Lance!

[Chevyaddicted]

I have a ?. I have a 69 camaro with a tci 4 link setup and torsion arm-bar swaybar. Is there enough room to mini tub it. My body guy doesn't believe it

[SSLance]

Car drove a LOT better today, part I'm certain was due to straightening everything with rear suspension out..the rest was the tires. I usually finish about 60-70th out of 100 cars or so in raw time...38th out of 97 cars today!!

Didn't get much good video today, here's the best of the best anyway though.

http://youtu.be/_In4Y378zHo

[4WardInv]

Nice job, having fun is what it's all about!

[SSLance]

Got the car back on the lift last night for the first time since the runs with the slicks...

https://static1.pt-content.com/images/pt/2013/04/IMG_20130423_190107_768-1.jpg

https://static1.pt-content.com/images/pt/2013/04/IMG_20130423_190225_236-1.jpg

If you listen on this video at 1:24 and 2:28 you can hear the left rear tire up against the tailpipe and the frame.

https://docs.google.com/file/d/0B1Fna3tdIX0ubF9KZXRzV0dWcEE/edit


I've got a few ideas, but I'm very limited in options due to time and $$ constraints.

The tailpipe is the biggest hindrance and the whole exhaust is loose yet again, so that'll be my first challenge to tackle.

[SSLance]

Just to update my progress on dialing the car in, I ended up pressing in 3" long wheel studs in the rear axles and swapped out the 1/4" spacer for a 1/2" spacer to get the rear Hoosiers to keep from rubbing the frame. I also rearranged the tailpipes and welded them all up solid to keep them in place and off of the tires and suspension.

After 4 weekends of autocrossing and one long track day weekend, all of that seems to have held up well and the car is performing better.

Here is a video of my 4 runs from yesterday's KCR Event 6 taken by the trackmaster app on my phone.

http://youtu.be/4q4Nk0aVJys

Course was a bit tough at first, had me all discombobulated...but I got the hang of it pretty quick and ended up with a raw time of 23rd fastest out of 97 entries on my last run.

This video is from my GoPro outside the Driver's window on the last and fastest run.

http://youtu.be/CGmS5lSUgQs

I think the car is running well enough now, I can take a break from wrenching on it for a bit. Need to plan ahead and gather parts for a front brake upgrade as well as sort out my tire issues to get enough rubber under the car to last me the rest of the year.

[Ron Sutton]

Hi Lance,

First ... congrats on improving your performance & results at your last AutoX.

Second, hats off for showing your videos & set up info so everyone can learn from it.

If you're open to some advice, I have some tips that may make your Monte perform better at the AutoX track. Let me know?

[SSLance]

Absolutely Ron, as a newbie at all of this I'm always interested in learning more about how to make the car run better...especially from someone like yourself.

[Ron Sutton]

This thread is about Measuring & Modifying Your Front Suspension Geometry:
For a thread focused on: Overall Handling & Tuning for Track Performance ... click HERE (https://www.pro-touring.com/threads/111962-Overall-Handling-amp-Tuning-for-Track-Performance).
For a thread focused on: Front Suspension & Steering Geometry for Track Performance ... click HERE (https://www.pro-touring.com/threads/111963-Front-Suspension-amp-Steering-Geometry-for-Track-Performance).
For a thread focused on: Rear Suspension & Geometry for Track Performance ... click HERE (https://www.pro-touring.com/threads/111964-Rear-Suspension-amp-Geometry-for-Track-Performance?p=1105096&posted=1#post1105096).
For a thread focused on: Designing Aerodynamics for Track Performance ... click HERE (https://www.pro-touring.com/threads/101460-Designing-Aerodynamics-for-Track-Performance).
For a thread focused on: Safety for Pro-Touring Track Cars ... click HERE (https://www.pro-touring.com/threads/103597-Safety-for-Pro-Touring-Track-Cars?highlight=track+safety).
For a thread focused on: Brake Selection ... click HERE (https://www.pro-touring.com/threads/104584-Brake-sizing-and-selection-tutorial-featuring-Ron-Sutton-and-Tobin-of-KORE3).

---------------------------------------------

Cool Lance!

Glad to hear it & I’m looking forward to working with you. :cheers:

Before we get into solutions, I want to share with you a viewpoint to make tuning easier. Competition cars are COMPLEX. There are literally over 200 AREAS of things to tune in the suspension alone. What helps a Tuner/Crew Chief to become more confident is ... knowledge (of course) ... experience (of course) ... knowing what a mechanical change actually effects on track … and how each tuning change of affects other areas.

But also, as a Tuner/Crew Chief, having a viewpoint that makes all this complexity ... simpler to understand … provides clarity & builds confidence.

I have developed many crew chiefs over the years to work with me on my race teams. Teaching them everything they need to master is a long term commitment on my part & theirs. It takes years. But simplifying things help them grasp concepts quicker ... and develops confidence in their tuning decisions.

Let's simplify things first. Remember this little corny phrase: 4x4x2+2 :secret:

It is short (like an acronym, but using numbers) for ALL the things that competition car Designers, Tuners & Crew Chiefs deal with. There are 4 key areas with 4 major ingredients, operating in 2 worlds … plus 2 wild cards. 4x4x2+2 is just a simple way to remind us what we're dealing with.

The 4 key areas are: power, braking, handling & aerodynamics (in no particular order.) Obviously these all play a role in the performance of the car … and in many cases affect each other.

Each Key area has 4 major ingredients that define it & of course effect it.

For power, the 4 major ingredients are:
Airflow
Fuel management
Spark control
Structure Design

For braking, the 4 major ingredients are:
Hydraulics
Leverage
CoF
Structure Design

For handling, the 4 major ingredients are:
Tires
Weight transfer … to and from tires
Geometry affecting … the tires
Structure Design

For aerodynamics, the 4 major ingredients are:
Force
Drag
Turbulence
Structure Design

When I said competition cars operate in two worlds, what I really mean is we do a lot of design, set up & tuning to the car in a “static state” … then go race it … and everything is affected & different when the car is in a "dynamic state" on track.

No pun intended, but the 2 wild cards are the track & the driver. The track environment is constantly changing, and good Tuners/Crew Chiefs tune to the changing conditions.

As long as we use human drivers, this will be a variable. Some drivers are more consistent & some less, but none of them are robots, so there will be inconsistencies. Some drivers are learning & improving, some not & even some declining in their abilities, but again, they are not static. Some drivers are more of a wild card than others.

:drive2:

As long as we simply embrace these 4 key areas, understand the 4 major ingredients that define & affect them, remember the car is acting in a dynamic state on track & account for the 2 wild cards … the job of Tuner/Crew Chief gets more clear, less daunting and making tuning decisions becomes easier, quicker & more confidently.

[Ron Sutton]

From watching your videos of all 4 tires, I see things we need to do in the front & rear. As we do this, I'm not going to just say "do this" ... I'm going to share “why” … so you become a better tuner & racer. So with each area, we'll discuss what's going on ... why ... what tuning change to make it better ... and why it makes it better.

There are 3 issues I saw from your videos.
1. As you turn the front wheels more, your tires lose the contact patch & go into a push condition in the middle of some turns ... until the corner speed comes down enough that the tries regain grip.

2. The mid-corner push is contributing to the car to snapping loose on the exits.

3. The rear tires are hopping when loose, compounding the loss of rear tire traction.

--------------------------------------

Causes … :attn:

1. Your caster-camber-camber gain-&-spindle KPI-SAI combination is not optimum for handling the tight corners of AutoX competition. WAY BETTER than stock … just not optimum yet.

The tire & wheel, on the outside of corners, goes into a state of positive camber (bad for the outside tire) … rolling over on the outside part of the tread and sidewall of the tire … with the inside part of the tread becoming unloaded. Basically, at this point, the actual tread making contact with the pavement (contact patch) gets narrower, making it incapable of maintaining the speed it was capable of an instant earlier, when it had more contact patch.

The tire & wheel, on the inside of corners, goes into a state of negative camber (bad for the inside tire) … rolling over on the inside part of the tread and sidewall of the tire … with the outside part of the tread becoming unloaded. Also making the contact patch narrower, making it incapable of maintaining the speed it was capable of an instant earlier, when it had more contact patch.

Hence … the push or understeer condition. :banghead:

The amount of camber error is minimal with slight amounts of steering input on large sweeping corners, but grows exponentially worse with higher rates of steering input (front wheel steering angle) on tighter corners.

*Re-watch your video & watch the front wheels lean when you have a lot of steering input in the car.


2. A mid corner push causing the car to snap loose on exits is VERY common. Once the pushing car slows down enough the that the front tires regain traction, it upsets the car, and tires, which were already at their limits. Once the front tires grab, most of the weight transfer goes to the outside front tire … and weight transfers off the inside rear tire … loosing grip on that tire … making the rear step out.

3. The spring rate and shock valving are both too weak on the rear to control the tire & wheel … over the rough surface … once the car goes into a loose condition. This is compounded by the mid-corner push. Once the front tires grab, most of the weight transfer goes to the outside front tire … but some of it goes to the outside rear tire … overloading that soft 125# spring & soft shock valving.

[Ron Sutton]

Solutions: :smoke:

1. The key to making a competition car carve corners well, is keeping the front tires’ full contact patches on the ground while cornering, regardless of steering angle. This is achieved with optimum front suspension geometry, which is often discussed but rarely fully understood.

For this conversation, we can leave out discussion of roll center (static & dynamic), roll center migration, CG, etc.

The focus here & now needs to be on camber, camber gain/loss, caster, caster gain/loss & the spindle’s KPI/SAI … and specifically the KPI/Caster Split ... then later bump steer, ackerman & toe settings.

I see from your front end alignment specs that you have static camber in the car (1.2 left & 1.5 right). I suspect, since you changed A-arms on the car that you improved your camber loss that is common with stock geometry & actually may have some degree of camber gain. :)

For those that don’t know about this … camber loss or gain happens as the front end compresses when cornering & or braking. In racing we call this “dive.” The camber loss or gain is a function of the lengths & angles of the upper & lower control arms, ball joint heights & spindle heights.

Technically, we state this backwards. Camber gain “in dive” is when the wheel goes into negative camber. Camber loss “in dive” is when the wheel goes into positive camber (bad). :confused:

Lance, if you know what your current camber gain or loss is, it will help our conversation.

Your caster shows at 5.7 LF & 5.6 RF. I suspect when you added that much caster over factory specs the car turned WAY better. Yes? :)

Your KPI/SAI shows 8.4 LF & 8.8/8.9 RF.

For those that don’t know what this is, KPI stands for King Pin Inclination & SAI stands for Steering Angle Inclination. They mean the same thing. KPI was a term coined back in the day of solid front axles when spindles actually used king pins. Steering Angle Inclination is a more correct modern term & is calculated simply by running a theoretical line through the upper & lower ball joints & comparing that angle to the actual spindle pin the hub spins on (rolling axis in the photo). (I use both terms because many race car guys are used to the older term of KPI.) See photo.

77428



By the way Lance … your spindles are both “supposed to be” the same at 8.75 degrees from the factory, but to say they vary from manufacturing tolerances would be like saying Bob Johnson likes telling jokes. :lol:

Most everyone knows camber, caster & KPI/SAI work together, but most don’t really understand HOW they work together & how they affect each other. I’ll do my best to explain it, but we’ll need to peel the onion one layer at a time, so bear with me.

Let’s start with Spindle KPI/SAI. In some racing classes, and in street cars where there are no spindle rules, we can run custom spindles & I design in the KPI/SAI I want. Other times, we’re working with a factory spindle & need to work around those parameters.

Your left spindle has 8.4 degrees of KPI/SAI … and if you were to set both the caster & camber at zero … and rotated the spindle 90 degrees each direction … the difference would be 2x the KPI/SAI angle … so in this case 16.8 degrees.

We know the wheels don’t turn anywhere near 90 degrees, but this example makes everything more clear. Please humor me & follow along closely, because I’m about to share something that is one of the most overlooked keys to proper cornering set-up. We will account for the ACTUAL steering turning radius later.

If you rotate the spindle 90 degrees toward the front (like the wheel is turning on an outside corner) the tire & wheel experience 8.4 degrees of camber loss (goes into positive camber). Bad, very bad for the outside tire of a corner. :evil:

If you rotate the spindle 90 degrees toward the rear (like the wheel is turning on an inside corner) the tire & wheel also experience 8.4 degrees of camber loss (goes into positive camber). But this good for the inside tire of a corner. :)

Reminder, we not turning the wheel 90 degrees in the real world, so don’t lock in on the numbers “too much”.

Caster is different. If we set caster at 8.4 degrees positive (top to the rear) & leave KPI/SAI out of the equation, as if we had a spindle with zero KPI/SAI … and you rotate the spindle 90 degrees toward the front (like the wheel is turning on an outside corner) the tire & wheel experience 8.4 degrees of camber gain (goes into negative camber). The right direction for the outside tire in a corner.

If you rotate the spindle 90 degrees toward the rear (like the wheel is turning on an inside corner) the tire & wheel experience 8.4 degrees of camber loss (goes into positive camber). And this is the right direction for the inside tire of a corner.

So … caster helps both the inside & outside wheel. :)

Here’s the most important piece of info to know at this point. It is the first & most important key to getting the front tires to use their full contract patch when cornering … increasing front end grip & turning speed. Drum roll please …

Caster offsets KPI/SAI on the wheel & tire on the outside corner … and compounds (adds to) KPI/SAI on the wheel & tire on the inside corner. :)

Read that again.

:1st:

This is called KPI/Caster Split. When the Caster & KPI are equal the caster offsets the negative effects of the spindle KPI on the outside wheel ... and compound the advantages of the KPI on the inside wheel. When the KPI is greater than the caster, unless the car has a TON of Camber, the outside wheel is going to lose camber as the steering is turned & roll over on the outside front tire. Ugly.

The greater the split, the worse the problem. On the other hand if the caster is slightly greater than the KPI, the outside wheel is going to gain camber as the steering is turned, creating a flatter, better tire contact patch. The inside wheel also gets cambered the correct direction (for the inside wheel) and both front tires have more grip, better turning & higher corner speeds.

Sooo … if we set the car up using spindles with 8.4 degrees of KPI/SAI and 8.4 degrees of caster … and you rotate the spindle 90 degrees toward the front (like the wheel is turning on an outside corner) the tire & wheel experience 0 degrees of camber gain or loss. Frankly it is zero, no matter what degree you rotate it to the front, because 8.4 degrees of caster counteracts or neutralizes the 8.4 degrees of KPI/SAI. :idea:

If you rotate the spindle 90 degrees toward the rear (like the wheel is turning on an inside corner) the tire & wheel experience 16.8 degrees of camber loss (goes into positive camber). This is the right direction for the inside tire of a corner … way too much ... but we’re not turning 90 degrees. We’re turning somewhere from 0 to 25 degrees. What if the wheels were turning 15 degrees? … that’s 1/6 … times 16.8 … is 2.8 degrees … the right direction. :idea:

You’re probably going “Hmmmm” … but we don’t have the whole picture yet.

Camber gain & roll angle are next. Camber gain (towards negative) helps the contact patch for your outside tire & hurts the contact patch for the inside tire.

If you worked out your camber gain to be 2.0 degrees towards negative “in dive” on the outside tire … and add that to the combination of your caster & KPI/SAI angle of zero … and factor in the car has a roll angle of 1.5 degrees … you would have 0.5 degrees of true camber, the correct direction. :)

The inside tire, of this car in the same corner, did not compress as far, so it doesn’t have as much camber gain towards negative (reminder: camber gain towards negative is bad on the inside tire). Let’s say we end up with 2/3 the travel … so 1.3 degrees (the bad direction) which would be correct for a 1.5 degree roll angle. Combined with 2.8 degrees (the good direction) from the combination of caster & KPI/SAI … and account for 1.5 degrees of roll angle (the bad direction)… and we end up with the inside tire dead zero … 0.0 degrees of true camber. :)

So … hard in the corner … in dive, wheel turned hard for a tight corner … the inside tire is 0.0, straight up … and the outside tire has 0.5 degrees of camber the correct direction. :)

Now, here is another part I love. If that’s not enough, you simply add caster. And from this point the math is easy. If you add 1.0 degree of caster … the inside tire has 1.0 degree of camber the right way… and the outside tire has 1.5 degrees of camber the right way … and so on.

The next tip is about static camber. If through setting caster, KPI/SAI & camber gain, you get the tires keeping optimum contact patches on the track, you do NOT need to build in static camber.

For oval track racing, using static camber makes sense because it’s easy. You’re tipping the LF tire out & the RF tire in (at top). You still have to work out your total desired camber number in dive & turning, but it’s easier. That won’t work for road racing & AutoX.

In road racing (or AutoX) where you’re turning left & right, static camber is like camber gain. It helps the contact patch on the outside tire & hurts on the inside tire. So, if you can achieve optimum contact patches with caster, KPI/SAI & camber gain, you do NOT need to build in static camber. :)

But … when you can’t achieve enough camber gain and/or can’t achieve enough caster, then by all means, use static camber to achieve optimum dynamic camber on the outside tire. Just know it is not ideal, because your giving up some tire contact patch & grip on the inside tire in every corner.

There is a little more involved in this, when you involve exact steering angles for specific corners. I use a spread sheet I developed to plug in all the info & know exactly what true camber I have at different steering angles & different camber gain & different suspension travels.

The best way I have found to work out a front end setting is to start with KPI/SAI & caster … then bring in camber gain … and finally static camber … to achieve the optimum TRUE dynamic camber for BOTH tires.

It probably is clearer now why getting advice on one setting that worked for a buddy’s car … without knowing the whole picture … can be misleading. As a tuner, I couldn’t imagine setting the caster without knowing the KPI/SAI & camber gain … and then of course testing on track with tire crayon on the edges every run (plus taking tire temps).

It’s been said a zillion times. It’s the whole package, not one part or one setting.

----------------------------------------

Solutions for the other two areas are simple …

2. If you cure the mid-corner push … you will eliminate the “snap loose” condition on exits. I’m not saying the car won’t, or can’t, be loose on exits. You can make it throttle loose. But it will quit “snapping loose” caused by the car’s upset balance when the front tires regained traction all of a sudden after pushing.

3. The spring rate of 125# is just a little too soft in the rear. It needs 150# rear springs for your AutoX track. This will help in other ways too. :)

The shocks are too soft on valving, but they’re not the cause of the problem. They just not helping solve the problem. They need to be rebuilt, replaced or upgraded, depending on your goals & budget.

If you rebuild or replace them, I can give you some tips on shock valving that will help the car AutoX better.

--------------------

Whew! That’s all for now. If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[benno505]

be back in a year i have to try and learn what ron just said haha.

[Ron Sutton]

Lance,

After you absorb that some ... the suggestion for problem #1 is to increase your caster for the spindles you have ... or potentially get different spindles with less KPI/SAI ... but either way, work out a combination of Spindle KPI/SAI, caster & camber gain ... to achieve optimum contact patch with your front tires.

If you're game, we'll need to discuss method options & target #s.

Best wishes.

[SSLance]

https://static1.pt-content.com/images/noimg.gif

Lot to digest there... I read it once, now I'm going back to read it again.

Ron I think I remember the alignment shop guy telling me that my static camber was 1.5 degrees negative and with 15 degrees of steering input it went to 2.5 degrees negative after the alignment with the new arms. We did not get into dive though.

Not sure if you can tell anything by this but I'll pass it along as something I did after putting the DSE upper control arms on the car.

http://youtu.be/i0haoUpFmPs

http://youtu.be/XcvkHx8LXYM

When I made those changes I wanted to record how those changes were different than the stock pieces and this was the best way I knew how, crude but a start.

I appreciate your taking the time to lay all of that out above Ron. I've heard and read bits and pieces about front end geometry before and it is starting to sink in more and more, but the way you lay it out helps makes things even clearer.

I have one question to ask, and not that it will make any difference to me in a real sense...but how will setting a front end up like you are describing above for optimum handling on an autocross course effect every day street driving? Will an alignment (or a complete front end setup) arranged for the best cornering be less than optimum for street driving both in tire wear and over all steering feel?

Now, back to reading again... :D

[SSLance]

Lance,

After you absorb that some ... the suggestion for problem #1 is to increase your caster for the spindles you have ... or potentially get different spindles with less KPI/SAI ... but either way, work out a combination of Spindle KPI/SAI, caster & camber gain ... to achieve optimum contact patch with your front tires.

If you're game, we'll need to discuss method options & target #s.

Best wishes.

That actually might be easy to try as my DSE arms came with slugs that fit into where the arm bolts to the frame. I believe I can pull the nuts, work the slugs out and put the new slugs in which should give me another 1.5 degrees of caster if I remember right?

[SSLance]

Lance,
or potentially get different spindles with less KPI/SAI ...


I'm curious what option I have in this regard if you are aware of any.

I am in the process of trying to upgrade my front brake package right now which is most likely going to mean modifications to my existing spindles. If there was a better option KPI/SAI wise that would also allow me to do a brake upgrade that might make pretty good sense right now.

[SSLance]

The amount of camber error is minimal with slight amounts of steering input on large sweeping corners, but grows exponentially worse with higher rates of steering input (front wheel steering angle) on tighter corners.

*Re-watch your video & watch the front wheels lean when you have a lot of steering input in the car.



I see that now after watching the video again, things look pretty decent and the car is sticking into the corner then with the extra bit of steering input for the sharpest part of the corner it all goes to hell. You can really tell when it happens by watching the tire roll under the rim.

It doesn't look like the ride height is changing much at this point, so am I correct in assuming the KPI has more to do with causing this than camber loss because of suspension compression?

And does the camber gain on the inside tire happen at the same point that the camber loss on the outside tire happens?

**back to reading**

[SSLance]

Sorry for breaking this up into individual posts but it's just easier for me to take it bit by bit.



Your KPI/SAI shows 8.4 LF & 8.8/8.9 RF.

By the way Lance … your spindles are both “supposed to be” the same at 8.75 degrees from the factory, but to say they vary from manufacturing tolerances would be like saying Bob Johnson likes telling jokes.



What can be done here to correct this other than changing stock spindles in and out until you get a pair that match and are in spec?

Or can this be adjusted for in caster and camber setting changes on the alignment rack?

I also can't imagine in my head looking at the diagram above how much difference there is between a 8.4 and 8.9 SAI?

[SSLance]

One last question before I get ready for work Ron, how can a lay person go about figuring out what the "camber gain" on his car is?

[Mizzouri]

Good stuff here! Lance it has been fun watching you run this season. Looks like you had a better Sunday than I had in my WS6 on that course.

[SSLance]

For some reason, me and the car just clicked on that course...I really liked it and had a lot of fun on it as well.

I need to make it a point to search you out at the next event and introduce myself. I keep scheduling myself to work Heat 0 and run Heat 1 and that is drastically taxing my time while there. I'm not going to do that anymore though if I can help it.

[SSLance]

Found these this morning Ron, not sure if they will help diagnose my cars ills more or better or not, but thought I'd throw them up just in case.

Last fall when I replaced the stock height front springs and 2" drop spindles with the 575# 2" drop springs and stock spindles, this was my alignment results right after, I just bolted the new A-Arms in place with the existing shim packs and took it to the shop for an alignment.

https://static1.pt-content.com/images/pt/2013/06/Alignmentspecs08242012-1.jpg





Then this spring I went back to the alignment shop after I replaced all of the rear control arms to set the pinion angle and recheck the 4 wheel alignment.

Nothing was changed on the front end settings. Only change we made on the rack was to adjust the Rear UCAs to raise the pinion angle about 3 degrees.

https://static1.pt-content.com/images/pt/2013/06/Alignmentspecs03142013_zpsbda36a31-1.jpg


I'm questioning to myself if the changes I made to the rear suspension had an effect on the front geometry, or if the driving of the car in several autox events last fall created some bushing deflection...or if it was just the alignment rack readings off just a bit to cause the slightly different readings when no changes were made up front mechanically?

It sure looks like something changed in the left front between the two alignments? Could possibly different amounts of gas in the tank have an effect on how the rear end sat and that cause the changes in the front readings?

[SSLance]

Geez...I have to go get some work done...

One more question though Ron...about my rear springs, you say I need a 150# spring instead of my 125#. How do I go about finding a 150# spring that is the right length to keep my ride height about where it is now?

That is a very easy change mechanically and probably not that expensive I'd guess...but I'd just like to make sure that the ride height stays
close to the same once installed.

When I had the 1" drop Eibach springs in the back (never found out what their rate was exactly) the whole car felt like it was pivoting on the front tires in turns, very unsettling. It kind of reminded me of back in the day when we'd jack up the back ends of our cars with air shocks to keep our fenders off of our wide tires on Cragar rims, looked great but performed horribly.

That feeling largely went away with the 2" drop 125# springs currently in the car, plus I really like the stance it has now.

[Ron Sutton]

I'm questioning to myself if the changes I made to the rear suspension had an effect on the front geometry, or if the driving of the car in several autox events last fall created some bushing deflection...or if it was just the alignment rack readings off just a bit to cause the slightly different readings when no changes were made up front mechanically?

It sure looks like something changed in the left front between the two alignments? Could possibly different amounts of gas in the tank have an effect on how the rear end sat and that cause the changes in the front readings?

The front reading variations ...between times on the test equipment ... are pretty normal & occur with variables in how the test equipment is installed on the car, minor wheel variations, etc. But you should be aware, settings can change from impacts, potholes, curbs & wear.

The only thing here that might be different on the front, caused by changes in the rear, would be slight variations in caster if you changed the ride height of the rear, affecting the car's rake, and therefore affecting A-arm & spindle rake.

I'm more concerned that something is out of square on the LR wheel. Your rear end housing is slightly bent up & forward, giving it camber & toe in. :eek:

When we build trick floater rear ends, we will sometimes build in a little camber, but you would want it the same on both sides ... or otherwise ... the car will handle differently on left turns versus right turns.

But the "toe in" of the LR wheel & tire isn't healthy. It isn't the end of the world, but down the road when you have some down time, I'd take the rear end to a chassis shop with a rear end jig & have them straighten the left tube.


If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[Ron Sutton]

Hi Lance,

I put come comments in blue, after your questions.

https://static1.pt-content.com/images/noimg.gif

Lot to digest there... I read it once, now I'm going back to read it again.

Ron I think I remember the alignment shop guy telling me that my static camber was 1.5 degrees negative and with 15 degrees of steering input it went to 2.5 degrees negative after the alignment with the new arms. We did not get into dive though.
That's good ... going the right direction ... but doing it "statically" at ride height only gives us part of the picture ... versus knowing what they are "dynamically" ... meaning in full suspension dive & with body roll at it's maximum. Static is helpful, just not complete.

Not sure if you can tell anything by this but I'll pass it along as something I did after putting the DSE upper control arms on the car.

http://youtu.be/i0haoUpFmPs
OMG ... great, simple video ... and you can clearly see you changed the car from having camber loss (going positive) to having camber gain (going negative) with the DSE arms.


http://youtu.be/XcvkHx8LXYM
Another great, simple video ... and you can clearly see you helped reduce the camber ills while turning ... by increasing the caster ... with the DSE arms that relocate the upper ball joint back.

Now ... you need to take this further, by adding more caster, to help correct the tire camber while "dynamically" in dive & turning.


When I made those changes I wanted to record how those changes were different than the stock pieces and this was the best way I knew how, crude but a start.
Love it.

I appreciate your taking the time to lay all of that out above Ron. I've heard and read bits and pieces about front end geometry before and it is starting to sink in more and more, but the way you lay it out helps makes things even clearer.
No worries. Glad to help.


I have one question to ask, and not that it will make any difference to me in a real sense...but how will setting a front end up like you are describing above for optimum handling on an autocross course effect every day street driving? Will an alignment (or a complete front end setup) arranged for the best cornering be less than optimum for street driving both in tire wear and over all steering feel?
For the most part, there are no negative results on the street. Improving or correcting camber, camber gain, caster, caster gain, roll centers, etc, all make the car drive better on the track & street.

One difference "can be" the toe setting.

Slight toe-in makes the car more stable at speed, but negatively affects steering response & cornering ability. Slight toe-out will make the car's steering response sharper, & improve cornering ability, but can make the car a bit "darty" at speed & will "wander" over rough surfaces.

In short track racing, tight corners in road racing & AutoX ... the optimum set-up will have the tires "toed-out" slightly in dive, with the wheels turned. There are three ways to achieve this.

1. Static toe-out
2. Built in Ackerman (or increased Ackerman)
3. Built in "bump out" when the car's suspension compresses "in dive"

I have done it all three ways & each has it pros & cons. If you set your car to have static toe out of 1/8" ... with no Ackerman & no bump out ... it will corner awesome, but cause excessive tire wear in everyday driving. It can "wander" on uneven roads & be a little darty.

If you set the car to have zero (0) toe (straight up, not toed out nor in) ... and have the bump steer dialed in to be zero throughout the usable suspension travel ... and build in enough Ackerman to achieve the same toe out of 1/8" "dynamically" in dive, while turning ... it will corner awesome (even better than static toe-out, but the difference is marginal) ... and the car will not have excessive tire wear in everyday driving. It "can" still "wander" & be a little "darty" ... but minor, & for sure less than with 1/8" toe out.

If you set the car to a small amount of toe in (1/16" total) ... and have the bump steer dialed in to provide "some" bump-out as the car's suspension compresses in dive ... and build in enough Ackerman ... so the ackerman & bump-out COMBINE to achieve the same toe out of 1/8" "dynamically" in dive, while turning ... it will corner awesome. The car will not have excessive tire wear in everyday driving ... AND ... it won't "wander" or be "darty."

--------------------------------------------------------------------

This section is an Edit/add-on.

I want to add something to my answer about your question, "how will setting a front end up like you are describing above for optimum handling on an autocross course effect every day street driving?"

I left something out. When you optimize the front suspension geometry ... meaning KPI/SAI, caster, caster gain & camber gain ... you do NOT need to run as much STATIC Camber ... which is a benefit to tire wear on the street.

--------------------------------------------------------------------




Now, back to reading again... :D
I understand. There is a lot to digest here.



If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[Ron Sutton]

That actually might be easy to try as my DSE arms came with slugs that fit into where the arm bolts to the frame. I believe I can pull the nuts, work the slugs out and put the new slugs in which should give me another 1.5 degrees of caster if I remember right?

That would be a good, easy, no-cost improvement. Adding 1.5 degrees to the 5.6/5.7 you currently have will put you a smidge over 7 degrees. Anytime you can reduce the KPI/Caster split, the tires contact patches will improve. :naughty:

You will need to reset the toe. And this WILL effect bump steer. :look:

Has your car had the bumpsteer corrected? Regardless, bumpsteer should be one of the things we work on, after you get the rest of the front suspension geometry optimized.

Regardless, add the caster & set the toe-out to 1/8" (only for now) ... then go run it at the AutoX & see how it performs. I'm confident it will corner better for you. When you feel the result & see the lap time gain, our next step will be to get the caster more than the KPI/SAI and really cut the tight corners!



If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[SSLance]

The bumpsteer never has been real bad with this car and got much better with the addition of the DSE arms. It is real nice to drive down the highway now as it sits.

I believe the only issue I will run into adding the extra caster might possibly be a rubbing issue on the back of the fender wells, won't really know until we try it though and it won't be the first time these have been touched by the tire.

I don't mind putting it on the alignment rack once again and I have until June 30th before the next AutoX event. My new front street tires came in today and hopefully I'll have them on the car by tomorrow. What I think I'll do is try to get the slugs in the arms maybe this weekend and then take it back to the alignment shop next week and go ahead and work to get the caster more than the KPI/SAI and the toe set all in one shot.

While it is on the alignment rack, can we maybe put a rachet strap on the K member and pull the front of the car down compressing the suspension to check the camber gain? I'm all about combining projects to gather as much information as I can at a time. The shop I go to is full of racers and charges by the hour and doesn't mind me helping while the car is on the rack.

[Ron Sutton]

I'm curious what option I have in this regard if you are aware of any.

I am in the process of trying to upgrade my front brake package right now which is most likely going to mean modifications to my existing spindles. If there was a better option KPI/SAI wise that would also allow me to do a brake upgrade that might make pretty good sense right now.

Lance,

There are a ton of spindle options ... way more than most people know. I think of them in 4 categories:
1. Factory spindles from another application.
2. Off-the-shelf aftermarket spindles, typically with lowering built-in
3. Off-the-shelf racing spindles, in standard & lowered heights
4. Custom spindles

There are several factors to take into account in spindle design:
a. Overall height & the individual distances from the spindle pin to the top & bottom ball joint mounting surfaces. (which is how lowering spindles are achieved)
b. KPI/SAI (King Pin Inclination or Steering Angle Inclination, depending on the term you're familiar with.)
c. The ball joint tapers & sizes ... but there are relatively easy to change & I don't let this prevent me from picking a spindle I want.
d. Steering arm length ... way more important they many realize.
e. Steering arm height ... as it affects wheel/tire clearance & what's required to get bumpsteer correct.
f. Amount of Ackerman built into the steering arm.
g. The actual spindle pin diameter & length ... affect strength & therefore spindle deflection ... critical in dive on hard, fast corners.
h. What bearings it uses ... affecting strength, load capacity & therefore high speed cornering safety.
i. What hubs it uses ... affecting weight, strength, wheel fitment, brake rotor placement, etc.
j. What brake calipers fit & how.
k. Weight ... its unsprung ... so it matters more. But it's not "rotating" ... so not as critical as wheels, tires & brake rotors.

Soooo ... yeah ... there are a lot of variables & spindle options. :rolleyes:

When I'm designing a front suspension for a specific class with rules on what spindle we can run, I pick the best spindle available under the rules and design everything else to either fix or compliment that spindle. Factory spindles usually have a lot of KPI/SAI. When I have to run a factory spindle, like yours, around 8.75 degrees of KPI/SAI ... I know I'm going to end up with 10 degrees of caster ... or more.


Remember the KPI/Caster Split concept ... if the caster is slightly greater than the KPI, the outside wheel is going to gain camber as the steering is turned, creating a flatter, better tire contact patch. The inside wheel also gets cambered the correct direction (for the inside wheel) and both front tires have more grip, better turning & higher corner speeds.

I designed & raced NASCAR modifieds with 8.75 KPI & 10-10.5 degrees of caster with awesome results. We had a crew chief go off the range with set-ups & try 6-7 degrees of caster, but the cars always pushed in mid corner ... and snapped loose on exit. He was used to running less caster, but didn't take into account the KPI/SAI of the spindles we had to run. :banghead:

The whole combination of KPI/SAI, caster, caster gain, camber, camber gain, Ackerman, toe, steering ratio, etc. ... ALL have to be designed together for optimum cornering performance. All of them are important, but the KPI/Caster split is critical.

When I'm designing a front suspension with no rules on what spindle we can run, I design the spindles & have them built. Then I'm not trying to fix anything :cool:

... and everything else in the front suspension can be designed to compliment that spindle. For a road racing car, I designed the spindle with 3 degrees of KPI/SAI ... and designed the rest of the the front suspension around what is called a "zero scrub" set-up ... & we ended up with 4.0 degrees of caster for optimum handling. This car did not require a high caster number, because the spindle KPI was lower. What is optimum for tight cornering is having the KPI/Caster Split slightly favoring the Caster.

Another successful car I designed with 5 degrees of KPI/SAI ... ended up with optimum handling with 6.5-7.0 degrees of caster ... depending on the track. Again, the key was the KPI/Caster Split slightly favoring the Caster.

This higher amount of caster seems odd to most mechanics & street car guys, but when you look at the newer Corvettes you'll see they run a lot more caster than what most think of as "typical" in the 1.5-3 degree range. The Factory GM specs for the C6 ZR1 is 7.7+ degrees of caster, with a 9.15 degree KPI spindle. The KPI/Caster Split is LOW, but still slightly favoring the KPI by 1.45 degrees. But owners that compete & win in the C6's increase the caster to 9.5-10.5 degrees of caster ... with the KPI/Caster Split slightly favoring the Caster.

The common thread is we are almost always running more caster than KPI/SAI ... if we can. We run smaller KPI/SAI where we can too ... but it requires running wheels with more back spacing to get the scrub radius low (or sometimes zero). So simply ordering a spindle with smaller KPI/SAI is not a bolt-on solution.



...

:hmm:
...

:hmm:
...

Yeah I know ... lots of information & no answer on what spindle you should run. The answer .... for now ... is it depends on your goals, plans & budget. We can make the suspension work better without changing spindles. But, if upgrading your spindles make sense for your goals, plans & budget ... Here is what I think ...

a. For your specific car & application ... stay with a KPI/SAI around 7-8.75 degrees ... or the scrub radius will get ugly.
** Less KPI/SAI would require different wheels with more backspacing & longer upper & lower A-arms for a good scrub radius. That is how I would build an Road Race & AutoX killer ... BUT, if I understand your goals & car usage ... that doesn't fit. Stick with 7-8.75 KPI/SAI.

b. A taller spindle ... combined with the the right height BJs ... would allow you to improve the roll center location & improve camber gain ... and then use spring adjusters to keep the car at the height you desire. Of course where it is taller ... and the dimensions from spindle to BJ pads ... are critical.

c. You could go with a lowering spindle ... ONLY if you want to lower the car. But you'll need to lower the rear too. Or utilize a std height lowering spindle ... which moves both ball joint pads down ... and run a long upper BJ ... creating in effect a taller spindle ... improving the roll center location & camber gain ... and use spring adjusters to keep the car at the height you desire.

d. A shorter steering arm would be beneficial. It would quicken up the steering without having to buy a new steering box. :yum:

e. You need Ackerman for your application, so exclude any non-ackerman spindles.

f. You are getting significant spindle deflection, so if you could get a bigger spindle pin, that would be beneficial.

g. Getting larger bearings ... especially on the outer hub bearing ... would improve both performance & safety.

h. You need a spindle that will allow 11.75-12.19" rotors. You can go with bigger rotors, but I wouldn't for your AutoX & street application. Just get the correct M/C, calipers & pads ... along with quality, curved vane rotors ... and you'll have all the braking force you need ... all the braking force your tires can handle ... without adding unnecessary rotating weight.


Hmmm. I'll need to do some research, compare available spindles & see what fits this criteria best. I'll get back to you tomorrow.


If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[SSLance]

So swapping out the plugs on the A arms to gain caster won't work, I've already got the offset plugs in the passenger side. I'd forgot we did that during the first alignment.

Here is the current shim stack on the Passenger side

https://static1.pt-content.com/images/pt/2013/06/IMG_20130613_195741_556-1.jpg


Here is the current shim stack on the driver's side


https://static1.pt-content.com/images/pt/2013/06/IMG_20130613_195759_216-1.jpg


And I did get my BFG Rivals put on the front this evening and was able to take the car out for a cruise on the street...first time in over a month. Man I like driving this car.


https://static1.pt-content.com/images/pt/2013/06/IMG_20130613_194710_233-1.jpg

[Ron Sutton]

I see that now after watching the video again, things look pretty decent and the car is sticking into the corner then with the extra bit of steering input for the sharpest part of the corner it all goes to hell.
Yup! Sure does. Glad you can see it now too.

You can really tell when it happens by watching the tire roll under the rim.
Correct. The initial "tightness" you feel in the steering wheel before it breaks into a push indicates the tires have gripped at their limit & the front end of the car is at it's maximum roll angle ... which COMPOUNDS the problem. If your car is rolled over 2.5 degrees ... that is 2.5 degrees of camber lean the wrong direction.

When the KPI/SAI being greater than the caster ... more steering input makes outside tire & wheel LEAN OUT at the top, known as losing camber (technically called going positive). My rough calcs say it is probably at 2.7+ degrees (at 20 degrees of steering input) ... the wrong way. Not only does the tire "roll under" ... but the contact patch narrows immediately ... and a lot. Probably going from 8" of tire contact patch to 5-6" ... maybe less.

If you were at the limits of tire adhesion ... with 8" of contact patch ... and that shrinks to 5-6" (25% less tire) ... at speed, under maximum load, in the corner ... well ... the front tires immediately break traction and the car goes into a push/understeer condition.


It doesn't look like the ride height is changing much at this point, so am I correct in assuming the KPI has more to do with causing this than camber loss because of suspension compression?
You are correct again. More KPI/SAI than Caster is the cause, not more body roll.

Here's why it happens.

Before the car breaks into a push ... the tires were gripping at their absolute limit ... therefore the front end of the car is at it's maximum roll angle ... MEANING the outside front spring is loaded as HARD as it is going to be. The spring is at maximum compression for that corner.

Then, as you give it more steering input ... and more KPI/SAI than caster causes the tires contact patches to shrink ... causing the tires to break traction & push. The car does not roll over any further. It can't ... it just lost traction. No traction = no body roll.

The outside corner will actually start to come up a little & the car will flatten out a little ... meaning the chassis/body roll actually reduces ... but only a small amount, say fraction of a degree ... until you unwind the steering wheel to exit the corner.



And does the camber gain on the inside tire happen at the same point that the camber loss on the outside tire happens?
Yes. So you're losing contact patch on the inside tire too.

I like to think of it this way ... there is no way a car driven at the true limits of tire adhesion ... with 16" of contact patch (both front tires) ... suddenly shrinking to 10-12" (again, both tires) ... at speed, under maximum load, in the corner ... can hold. The front tires are going to break traction to some degree and the car goes into a push/understeer condition.

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And then ... (sounds like a camp fire story)

When the front tires do regain traction, the outside front corner dips again, unloading the inside rear tire ... causing it to lose a degree of grip ... and you get the loose condition on exit.

As you can tell, push/understeer conditions are the worst thing for competition cars. I hate them, so I've spent my racing career understanding causes & cures.

The good news is your car is already WAY better than it was stock. With the changes you already made, you have made big steps at improving the handling. The even better news will come when you get the suspension fully optimized, and cure the small ills it has now. Better lap times & more fun at the track will be our result.

**back to reading**

Me too. I have more of your questions & comments to read ... plus some spindle research to do.

[Ron Sutton]

Hi Lance,


The bumpsteer never has been real bad with this car and got much better with the addition of the DSE arms. It is real nice to drive down the highway now as it sits.

I believe the only issue I will run into adding the extra caster might possibly be a rubbing issue on the back of the fender wells, won't really know until we try it though and it won't be the first time these have been touched by the tire.

I don't mind putting it on the alignment rack once again and I have until June 30th before the next AutoX event. My new front street tires came in today and hopefully I'll have them on the car by tomorrow. What I think I'll do is try to get the slugs in the arms maybe this weekend and then take it back to the alignment shop next week and go ahead and work to get the caster more than the KPI/SAI and the toe set all in one shot.

While it is on the alignment rack, can we maybe put a rachet strap on the K member and pull the front of the car down compressing the suspension to check the camber gain? I'm all about combining projects to gather as much information as I can at a time. The shop I go to is full of racers and charges by the hour and doesn't mind me helping while the car is on the rack.

A few things ...

1. I don't think you can get all the caster you need with your existing upper A-arms. I suspect the slugs in the upper A-arms will only allow you to come back a degree or so. To get more caster with the Upper A-arms, you will need different upper A-arms, with the upper ball joint moved back more than the DSE arms you have ... or you need different lower A-arms that move the lower ball joint forward. DSE makes Lower A-arms for your car that move the ball joint forward to add another 2-3 degrees of caster. That is the route I suggest. So there is a cost, and time.

2. As you lay the spindle back more, you're going to change the bumpsteer more. Your car hasn't been properly "bumpsteered" yet anyway (racer term for working out the bump steer on both side to achieve either zero bumpsteer, or a predetermined amount of "bump out" depending on your handling goals & preferred strategy). This requires specific small parts & takes AWHILE to dial it in perfectly. I'd hate to see you do it over & over every time you make a change, so I suggest you do it once, after we work out your front suspension package.

3. You're mentioned a brake upgrade & we discussed potentially changing spindles too. Could be some advantages, with a better designed spindle, as we discussed in another post. I suggest we weigh these out & decide the total package, and do it once ... and then dial in the bumpsteer.

4. We REALLY need to map out your front suspension geometry, which will tell us your current A-arm Instant Centers, Camber Gain, Scrub Radius, and both Static & Dynamic Roll Center locations. You will need to do all the measuring & get me the #'s ... and I'll enter them into the geometry program.

5. THEN ... with the DSE lower A-Arms (for sure) ... "probably" some different height ball joints ... and "maybe" a different spindle (or not) ... all to optimize your caster, KPI/SAI, Camber, Camber Gain & Roll Centers ... and we'll be able to pull your car's front geometry together for race car like handling on the AutoX course.


Cost estimations:

DSE Lower Control Arms $700
Special Height Howe Ball joints $150-300
Custom Spindles $500
Bumpsteer parts $120
Spring Adjusters $80

Digest that & we'll talk more next week.

[Ron Sutton]

So swapping out the plugs on the A arms to gain caster won't work, I've already got the offset plugs in the passenger side. I'd forgot we did that during the first alignment.



I see. So we won't be able to get much more out of the upper A-arm. But if we can get .4 of a degree with the uppers ... and with the DSE lowers, we can get another 2-3 degrees ... to add to your current 5.6 ... you'll end up in the 8-9 degree range. That will be "closer" to optimum with your current spindles. If we change to spindles with 7.5 degrees of KPI/SAI & get 8.5-9.0 degrees of caster, that will be real good.

If we dial in the right amount of camber gain, caster gain & Ackerman, then bump steer it ... you'll be golden.

I want to work out the scrub radius before I can confidently suggest spindles with less KPI/SAI. So getting the suspension pivot measurement numbers should be your next project before we try to lock down parts or specs.

[SSLance]

For some early Sunday morning reading, I went back and re-read everything Ron has discussed in this thread. As I'm getting a better handle on the terminology and the thought process behind suspension geometry, more and more is sinking in when I re-read his posts.





4. We REALLY need to map out your front suspension geometry, which will tell us your current A-arm Instant Centers, Camber Gain, Scrub Radius, and both Static & Dynamic Roll Center locations. You will need to do all the measuring & get me the #'s ... and I'll enter them into the geometry program.

[/B]


Ron, I'll be happy to do what I can here on this but I need a bit of direction from you on exactly how to measure and map out my suspension geometry to give you the information you need to see the whole picture.

[Ron Sutton]

Excellent. Tomorrow, I'll put together instructions & tips for you to measure all of the pivot points in your front suspension, track width, sway bar, shock & spring points in three dimensions.


You’ll provide me the measurements & I will input them into one of my suspension software packages & we’ll get clear on your CURRENT …
A-arm Instant Centers
Static Roll Center location
Dynamic Roll Center location*
Scrub radius
Camber Gain per inch
Dynamic Camber in dive & roll*
Spring Motion Ratio
Actual spring rate at the wheel
Sway Bar Motion Ratio
True rate of your Sway Bar
Shock Motion Ratio
Shock Valving rate at the wheel**

From there, we’ll be able to make informed decisions on A-arms, ball joints, spindles, etc … to achieve optimum geometry for your goals. So we can dial in the whole list above to the optimum settings (within physical possibilities). :)

I will show you how the information can guide us on part & tuning decisions, after we lay it out, along with what all the info means. If there are Engineers following this post, you’re going to dislike some of my terms. I apologize in advance. Sometimes I use the engineering term. Other times I use what I call “car guy” terms.


Notes from above:

* We can only do these after we know your shock travel on course. So for your next AutoX event (June 30th ?) you will want to use lowbuck shock measurement data acquisition devices ... known as rubber O-rings or zip ties (tied real tight) on all 4 shock shafts, pushed up against the shock body. As you run the course, each shock will travel & therefore move the rubber o-rings or zip ties down the shaft.

After each run & definitely before the next run ... measure & record your shock travels & the run # ... then push the o-ring/zip tie back up against the shock body. Do that for all of your runs & share the info with me online after the event. I'll show you how we use that info to determine a lot of key things.



** This would require dyno'ing your current shocks which I don't think is valuable, because they are close to worn out. But when you get new shocks, and we get a dyno sheet, we'll be able to use this info.

[Ron Sutton]

Lance, I think I remember you’re leaving town for a few days. Take this & digest, so you can plan to do this sometime after you return. This takes time & patience.

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In this post, I’ll lay out a method to measure all of the pivot points in your upper & lower A-arms … plus track width, sway bar, shock & spring points.

There are hundreds of ways to doing most things. I’m laying out one way I think most car guys can do in their garage. You will need some basic tools & creative body language when it comes to getting into difficult spots.

This method will take a little longer, but we will have accurate numbers … AND … as you make changes, you will need to take only a few measurements & we’ll still know where everything is.

These dimensions are important, so taking your time, measuring several times & even measuring different ways will insure we have accurate numbers.

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Tools:
You will need a good tape measure. Use just one … so if the end isn’t dead zero perfectly accurate, at least all the measurements are the same. Every 1/16” matters.

Tool check list or shopping list:
Good, readable tape measure.
4-6” dial or digital caliper.
Short laser level (6-10”)
String
2 Bob weights.
Chalk line (blue will come off your floor eventually. Red is not coming out … ever)
Roll of quality string
Removable masking tape (Blue 3M works best)
Sharpie fine point marker(s)
Brake Cleaner & paper towels
Note pad & pens

Sears has everything in one stop if you need something.

Laser levels
http://www.sears.com/shc/s/p_10153_12605_00948292000P
http://www.harborfreight.com/2-in-1-magnetic-torpedo-laser-level-67800.html

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Pre-measure Ball Joints:
If you have some spare upper & lower joints ... great. If not, make a stop at your local, friendly auto parts store where you buy parts. You’ll need to borrow an upper & lower ball joint to measure at the counter.

Lance, you need a Moog K5208 for the upper & Moog K6145 for the lower. Unless your DSE upper A-arms have a special ball joint in them. Call DSE & find out “for sure” as this is CRITCAL.


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Refer to the photos I’ve attached here. Take a ball joint & lean it all the way to the right & draw a Sharpie line on the housing … in line with the BJ pin. Now lean it left & do it again. Now straight up & do it. There is your true pivot center. Take your dial/digital calipers & measure from the pivot center to the top of the housing & again from the pivot center to the end of the stud.

Do both ball joints & write down all the numbers. When you’re under the car, getting to the top off the housing or the end of the stud will be WAY easier to achieve. You just need to do the math … along with measuring … to arrive at the true pivot center locations on your car.

What was the brake cleaner & paper towel for? To clean off your Sharpie marks on the ball joint housings. :)

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Before you start:
a. Plan for this to take half a day.
b. You’ll need a helper to hold the other end of the tape and to “spot” for you.
c. Work out how you’re going to put your weight in the seat. Don’t use a person. (We use lead)
d. Put your AutoX tires on & set the tire pressures just like you compete with.
e. Get the car as close to “race ready” as possible: fuel level, stuff out of (or in) the car, etc.
f. CRITICAL: Document all numbers & details on paper, so we can refer back later.

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Platform:
The tires & suspension have to be “loaded” just like the car is on the ground. So you can not use a chassis lift or jack stands. You can use a drive on lift.

The car needs to be on its tires, just like ride height, but you need to be able to get under it. We use 10” Joe’s Racing stands & simply add 10” to all of our height numbers.

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You “may” be able to do this on the garage floor, but it is harder. Depending on ride height you may not be able to get under the car well, or at all. If you’re doing this on the floor, pick a spot as flat as possible with no dips.

I’ve seen guys use car ramps & stands … shimmed so all 4 to the exact same height. I’ve seen guys with shops use muffler & oil change pits, where they can walk under the car. So give this some thought on where & how works best for you.

If you rig something up to raise the car, all 4 stands need to be the EXACT same height. Any height will do, but they have to be the same. Whatever the number is, you will be subtracting it from your height numbers to get true numbers, as if the car was on the ground.

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Pull the car into your “space” straight. Make sure the front wheels are “dead true straight” as you roll it in & do NOT turn the steering wheel once you’re in your spot. Back up & do it again if you need to.

A simple way to check & confirm the front wheels are “dead true straight” … is to pull a long, taut string across rear tire & front tire on one side … at the same height (preferably axle centerline) … and pay attention to how it lays across the front tire. Do both sides.

If the car is toed-in, the gap between the string & front sidewall, of the front tires, should be the same on both sides. If the car is toed-out, the gap between the string & rear sidewall, of the front tires, should be the same on both sides. If a gap is bigger on one side, the steering is not straight.

You don’t want to have to turn the wheels … in their spot … and leave them, as there will be “tire bind” (unless you have some way of freely sliding one wheel). Get it true & back the car up 2’ & roll it into place again if you need to.

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3 types of measurements.
1. Height … from the ground up to the pivot point
2. Left or right … always from the car centerline
3. Forward or backwards … of the front axle spindle centerline.

What you’re measuring … in order:
a. Car ride height.
b. Car centerline.
c. Front axle centerline.
d. All four ball joints ... at true center of their pivot.
e. All 8 A-arm pivot centers (2 for each upper & lower A-arm).
f. Shock pivot centers
g. Spring end centers
h. Sway bar attachment points to A-arms.
i. Track width

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Here is detail for each area of measurements.

a. Car ride height.
Pick a spot on the bottom of the frame rails that will be easy to measure now & in the future. The further apart you go, the more accurate. Most racers usually pick a spot in front of the rear tires & behind the front tires … if the frame rails are wide at that point & out near the rocker panel. Either pick a spot with identifying holes or marks on the bottom side of the frame rails … or make something to permanently mark these spots. You’ll use these for the life of the car, no matter what changes you make.

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b. Car centerline.

Before we start … “mark down” … means using either the laser or plumb bob & string … to put a mark on the floor exactly where a point is. Some people use the term “transfer” … meaning to transfer a point on the chassis or suspension onto the ground.

I don’t like marking on my epoxy coated floors, so I put blue masking tape down first & write on it with the Sharpie marker.

This measuring process is difficult & somewhat subjective. Pick a section of the frame that looks symmetrical … and either go inside or outside (but use the same on both sides of the car) & “mark down” … putting a dot or “x” on the floor. Do this in 3 spots, using 3 different sections of the front frame. Then, do this in the rear, using 3 sections of the rear frame.

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Now find the center of those 6 frame sections, using tape & sharpie again.

Next, with a friend’s help, pull your chalk line taut … down the center of the car … on the floor … and the string “should” hit all 6 frame section centers. If it doesn’t, either recheck your measurements and/or re-evaluate your choice of locations. Ultimately, you’re going to put a chalk line on the floor using the marks you trust.

That is the car centerline that everything is going to be measured from & to.

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c. Front axle centerline.

A simple way to do this is to pull a taut string behind the front tires, on the floor, and mark the string location on both sides. Do the same in the front. Split the difference & that is the front axle centerline. Problems only occur with this method with different tires, different pressures, suspension or tire bind from not rolling it into place straight.

Put a chalk line on the floor representing the front axle centerline. Many things, but not all, will need to be measured from & to this point.

For all things in front of the front axle centerline, express them in negative or minus numbers. Example: if something is 2 & 3/8” in front of the front spindle centerline, write it down as -2 & 3/8”.

Everything behind the front axle, express as positive numbers.


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d. Locate all four ball joints ... at true center of their pivot.

Since you have already pre-measured the ball joints, this part is not as tough as it would be if you were trying to find the pivot centers while measuring. Eyeballing these pivot centers ALWAYS leads to inaccurate data.

Use your measurements from the top off the housing, or the end of the stud, to the axle centerline & work out the math. Double check by eyeballing to see if your math places the pivot center where it actually is.
Your roll center locations & camber gain numbers will only be as accurate as your measurements. This is a time consuming & somewhat tedious operation. I always suggest people take the time to do it right the first time, so you don’t have to do it over (or suffer handling problems from incorrect tuning).

You need to measure the location of each ball joint in 3 directions … all based on the true pivot point of that ball joint. You need the …
1. Height … from the ground up to the pivot point
2. Left or right … always from the car centerline
3. Forward or backwards … of the front axle spindle centerline.

Reminder: for all things in front of the front axle centerline, express them in negative or minus numbers. Example: if something is 2 & 3/8” in front of the front spindle centerline, write it down as -2 & 3/8”. Everything behind the front axle, express as positive numbers.


I can’t stress this enough. Make sure your tape is both straight & a true 90 degrees to what you’re measuring. Having the tape measure angled any direction other than a true 90 degrees will produce incorrect numbers. This is hard to see when you’re holding the tape under the car in a tight spot.

Use your friend as a “spotter” to insure your tape is straight up & down for height measurements on 2 planes ... and 90 degrees to the car centerline & level for right & left distance measurements.

There are times when it is more accurate to …
• Use a tape and measure directly.
• Hang a plumb bob on a string off the point, or near it, and measure.

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• Utilize the laser (and level) to point up or down & transfer the measurements.
• Use the level to extend a point out to where you can use the tape measure.
• You’ll just have to use your best judgment or try it different ways.

I like to mark on tape on the floor … so I don’t forget (I’m old). I put “points” on the tape along with the measurement … so I can find the point again easily to re-measure if I want or need to … and so I can re-check my measurements.

I check my numbers & recheck them several times. So when I capture them all … I KNOW THEY’RE RIGHT … and can trust the data & results.

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e. All 8 A-arm pivot centers (2 for each upper & lower A-arm).

You need to measure the location of all 8 A-arm pivots in 3 directions … all based on the true pivot point of the bushing. You need the …
1. Height … from the ground up to the pivot point
2. Left or right … always from the car centerline
3. Forward or backwards … of the front axle spindle centerline.

For the upper A-Arms … you can simply measure off the ends of the pivot shaft. For the lower A-arms, I need you to measure each bushing bolt … on both sides … and average the numbers.

For example: If the center of the bolt at front of the driver side lower A-arm is 8-11/16” in the front of the bushing & 8-9/16” in the back of the bushing … you will average that to 8-5/8”. That is the height of that bushing.

When measuring from the car centerline, the differences are bigger, because the lower A-arm is angled a lot. So, from car centerline, if the center of the bolt in front of the bushing is 10-1/16” & the center of the bolt on in the back of the same bushing is 10-7/16” … you will average that to 10-1/4”. That is the distance from the car centerline to the centerline of that bushing.

If this same bushing is 1-1/2” ahead of the axle centerline on one side & 1-7/8” ahead of the axle centerline on the other side … you will average that to 1-11/16” … and because it is AHEAD of the front axle centerline, you need to express it as a negative, so write it as -1-11/16”

We need all 3 dimensions on all 4 bushings.

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f. Shock pivot centers

The process should be getting simpler by now. You’re measuring to find shock pivot point centers. We need all 3 dimensions on all 4 front shock bushings.

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g. Spring end centers

A little tricky to measure … but we need measurements from the center of the spring top … to the front axle centerline & car centerline … and the height.

We need the same thing for the bottom of the spring … and for both front springs.

** Anyone who is following along with us … if you have coil-overs … all you need to do is locate the shock pivot centers, as the spring does whatever the shock does.

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h. Sway bar attachment points to A-arms.

I saved the simple stuff for the last two. We do not need measurements for height or distance to front axle centerline.

For this part, all we need are accurate measurements from the center of the car to the center if the connection points on the A-arm.

** Anyone following along with us, if your sway bar has linkages that mount off the side of the sway bar arm … you want to measure to the center of the connection points on the A-arm … NOT the center of the sway bar arm.

Sway bar arm length matters to calculate your actual sway bar rate. So now is a good time to measure & record it. Measure from center of main sway bar to center of pivot on sway bar arm … 90 degrees from the main sway bar … regardless of angle or shape of the arm.

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i. Track width

Just for clarification … “tread width” is outside to outside of the tread. “Track width” is center to center. A lot of people get those confused & our conversations get sidelined.

We need to know the track width … the true center to center of the front tire contact patches. Several options, but here is a quickie.

On the front side of the tires … measure from the outside of the tread width on one tire … across to the inside tread width on the other side. Do the same on the back side of the front tires … and average the two numbers … to account for any toe in or out.

If you get 55-1/2 in the front & 55-3/8” in the rear, average that to 55-7/16”.

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Tips:
• Remember to subtract the distance you raised the car up from ride height for all height measurements.
• Reminder: for all things in front of the front axle centerline, express them in negative or minus numbers. Example: if something is 2 & 3/8” in front of the front spindle centerline, write it down as - 2 & 3/8”. Everything behind the front axle, express as positive numbers.
• Your roll center locations & camber gain numbers will only be as accurate as your measurements & small #’s make a big difference. I measure everything I can on my cars with a digital caliper to the thousandth. It is that important.
• Take your time & be precise. Don’t just “eyeball it.”
• Getting true measurements is difficult. Experiment & be creative with measuring methods, but be accurate.
• This a time consuming & somewhat tedious operation. I always suggest people take the time to do it right the first time, so you don’t have to do it over (or suffer from incorrect tuning).
• Because you got frame heights on 4 corners of the car, you will be able to make many adjustments to the car, and know what changed & where you are, by rechecking frame heights.
• For example, if you lower the whole car ½” … all of your frame mounted pivots just went down ½” … and your ball joints did not. That is easy to change in the roll center programs & know what your geometry is then.


When you have the numbers, post them here on the Forum in an order that matches the numbers in this photo. After I enter them all, I’ll run calcs & post the graph.

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We won’t be able to determine true roll angle or dive numbers until you get shock travel measurements from your June 30th AutoX event.

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If anyone has any questions, feel free to chime in on this thread.


Ron Sutton

[SSLance]

Oh my... https://static1.pt-content.com/images/noimg.gif

I have access to a drive-on lift at my office, so that will alleviate at least one of the more difficult parts of what I've read above.

Now I need to read it all again to try to absorb even more of it.

It does sound like a half day project at least, but not undoable at all.

Thanks Ron...I'll get started gathering things up.

[Ron Sutton]

LOL ...

Lance, work at your pace. I'm just here to help.

------------------------------------------------------------------

On another note, I have been doing some spindle research for you. I found spindles that achieve a slightly lower KPI & shorter steering arms, but overall they are too short for optimum geometry & big brake options are limited.

I found spindles that have the same KPI, are taller, use bigger bearings with a stronger spindle, offer better brake options, but are too long above the spindle & too short below it.

Lastly, I spec'ed out some custom spindles that do it all, but cost $600 with bearings, but will require a hub/rotor change. If you're upgrading brakes, it may justify the expense. Once we map out your front suspension geometry, I can better advise you if they'll be worth it or not.

A few advantages to think about for now are:
* Much quicker steering, without buying a new steering box.
* Bigger spindle pin & bearings ... safer, less camber deflection under load.
* 12" x 1-1/4" wide, combination rotor & hubs available drilled & grooved around $125 each.
* Easier to get the caster above the KPI.

Let me know if you have questions on measuring suspension points.


Ron Sutton

[SSLance]

After re-reading the above and thinking about how I'm going to do this, I do not think using a drive on lift is going to help. Sure it's the best way to get all four tires level and gain access to under the car, but I can't see how I can get accurate measurements to the floor with the lift ramps in the way?

I think I'm going to make a set of these.

https://static1.pt-content.com/images/pt/2013/06/20120715_164522_5261-1.jpg

and use a laser level to make sure I get them all exactly level and square on my slightly sloped shop floor and use my two post lift to set the car on them before starting the measuring process. My only other obstacle that I can think of right now is the linear floor drain that runs right down the center between the posts of my lift. I guess I can set my car up to one side or the other of it so the snapped center line has a clear surface to be on.

I also have to figure out a way to get the front tires to relax to a normal position once setting on the stands as it'll be hard to roll it back and forth once on them.

Ideas? I can NOT get under my car as it sits at ride height, heck it's hard enough to just get a floor jack under it to raise it up.

[Ron Sutton]

After re-reading the above and thinking about how I'm going to do this, I do not think using a drive on lift is going to help. Sure it's the best way to get all four tires level and gain access to under the car, but I can't see how I can get accurate measurements to the floor with the lift ramps in the way?

You can use a drive on lift. I have seen it used successfully many times & it is the easiest by far. In this scenario, you don't measure to the shop floor ... you measure to the lift "floor." Take a long string with bob weights on each end (or simply heavy bolts) and lay them across each ramp. That string line is a VERY good measuring point and can be easily moved to take measurements "almost" anywhere.

With this method, you are still putting all 6 of your frame measurements on the lift ramps, but then you run a long string (instead of a chalk line) & it hangs over the ends of the lift. Once you have the string at the car's true center, mark the ends of the lift where the string goes (just in case it moves). Use bob weights or heavy bolts to keep tension on it & tape it in place (duct tape here).

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Now you have a string running down the centerline of the car at ground level. Most old school chassis builders prefer this method. You can take your strings & weights that run overs the sides of the lift ramp runners & move them "almost" anywhere to get a measurement.

This method also works well with a laser lever set (level) on the ramp runners & pointed where ever you need a line. You just need to take the distance of the laser above the ramp runner into your math.

Another method for measuring a lot of the front suspension points that are near the front axle CL, is cutting a piece of STRAIGHT, square tubing (or angle) slightly shorter than the distance BETWEEN your front tires. You simply lay it on the ramp runners & move it anywhere you want to measure something ... running your tape to the bottom of it ... which is your floor.


I think I'm going to make a set of these.

https://static1.pt-content.com/images/pt/2013/06/20120715_164522_5261-1.jpg

and use a laser level to make sure I get them all exactly level and square on my slightly sloped shop floor and use my two post lift to set the car on them before starting the measuring process. My only other obstacle that I can think of right now is the linear floor drain that runs right down the center between the posts of my lift. I guess I can set my car up to one side or the other of it so the snapped center line has a clear surface to be on.

I also have to figure out a way to get the front tires to relax to a normal position once setting on the stands as it'll be hard to roll it back and forth once on them.

Ideas? I can NOT get under my car as it sits at ride height, heck it's hard enough to just get a floor jack under it to raise it up.

These wheel stands will work too. But not as easy or accurate as the drive on lift ... because the floor ... your real floor is not as straight as a a string. Having the drain in the middle sounds concerning, but you know it best. If you don't think the floor is flat & straight enough, I'd pick another option. If the floor is flat enough, of course it will work. But I still prefer the drive on lift.


If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[SSLance]

Drive on lift it is then...I can make that work.

Is it crucial for the lift itself to be exactly level?

[Ron Sutton]

No, it's not crucial for the lift to be exactly level. If the "floor" tilts more than 2-3 degrees, it may start to affect things, as the car will lean. Otherwise, you're just measuring height from "floor" to pivot points.

One tip though, and we do this when we are out at the track & can not make something level ... if you use a digital angle finder/level ... and learn your "floor" of the lift is 0.7 degrees to one side ... take that into account when & if you use a level to measure anything ... and set it at the 0.7 degrees the same direction.


If anyone has any questions, feel free to chime in on this thread.

Ron Sutton

[David Pozzi]

Ron, Great info here. Thanks for the input in our forum. I'm sticking this thread to the top of the forum index.

[Ron Sutton]

Thanks David.

Take care.


Ron Sutton

[Knoxferatu]

I'm fairly blown away by the generosity being shown here. What a great forum!

[SSLance]

Had some down time while away and an internet connection, so I logged in to reread the instructions so they would start to sink in more. I believe I'm starting to get the idea better and better all the time.

My main concern is how I'm going to get the measurements when things are in the way...but I'm sure I'll figure them out.

Thanks again for all of the knowledge sharing Ron and thanks to David for stickying the thread. Hopefully many of us can help blueprint our cars better with the info in this thread.

[Ron Sutton]

Had some down time while away and an internet connection, so I logged in to reread the instructions so they would start to sink in more. I believe I'm starting to get the idea better and better all the time.

My main concern is how I'm going to get the measurements when things are in the way...but I'm sure I'll figure them out.

Thanks again for all of the knowledge sharing Ron and thanks to David for stickying the thread. Hopefully many of us can help blueprint our cars better with the info in this thread.

If you need more clarity or guidance, don't be afraid to ask. The first time is always intimidating. After measuring a car or 2, it becomes just another car thing. Once you get the #'s, I'll work out your front end geometry & we will know where you are. Then I can work out ways to achieve your handling goals.

Take care!

[SSLance]

for your next AutoX event (June 30th ?) you will want to use lowbuck shock measurement data acquisition devices ... known as rubber O-rings or zip ties (tied real tight) on all 4 shock shafts, pushed up against the shock body. As you run the course, each shock will travel & therefore move the rubber o-rings or zip ties down the shaft.

After each run & definitely before the next run ... measure & record your shock travels & the run # ... then push the o-ring/zip tie back up against the shock body. Do that for all of your runs & share the info with me online after the event. I'll show you how we use that info to determine a lot of key things.




As far as measuring shock travel, you want the measurement from the moved zip tie on the shock shaft back to the shock body when the car is sitting at ride height in between runs correct?

I'm back home and planning out my shop time before Sunday and need to get the car on the lift to make sure I'll be able to get to all of the shocks to record this measurement in the grid between runs.

It looks like it is going to be super hot this weekend and I haven't had time to scrub in my new street tires yet, so I think I'll just run the slicks on all 4 runs Sunday.

[Ron Sutton]

As far as measuring shock travel, you want the measurement from the moved zip tie on the shock shaft back to the shock body when the car is sitting at ride height in between runs correct?
Yes.

Remember to push the zip tie back up against the shock body on all 4 shocks before each run.

Record the travel on all 4 shocks every run. When you post them, I'll show you little things we look for.

I'm back home and planning out my shop time before Sunday and need to get the car on the lift to make sure I'll be able to get to all of the shocks to record this measurement in the grid between runs.

It looks like it is going to be super hot this weekend and I haven't had time to scrub in my new street tires yet, so I think I'll just run the slicks on all 4 runs Sunday.

Okie dokie. Have fun in that heat & humidty. :poke:

[SSLance]

Uh, this might be an issue...

https://static1.pt-content.com/images/pt/2013/06/IMG_20130628_200530_876-1.jpg

That is the right front shock, zip tie installed and car let down to sit at ride height, then raised back up for the picture.

This is the left front

https://static1.pt-content.com/images/pt/2013/06/IMG_20130628_200348_890-1.jpg

Here's the backs same scenario

https://static1.pt-content.com/images/pt/2013/06/IMG_20130628_200315_232-1.jpg

https://static1.pt-content.com/images/pt/2013/06/IMG_20130628_200302_652-1.jpg

[SSLance]

Okie dokie. Have fun in that heat & humidty. :poke:

Sunday, 30

75 | 55 °F
Partly Cloudy

I think I can handle that. :D

[Ron Sutton]

Sunday, 30

75 | 55 °F
Partly Cloudy

I think I can handle that. :D

Oh man ... I'm jealous. Here in Sac-ra-tomato it will be 106 on Sat & 108 on Sun.

[Ron Sutton]

Uh, this might be an issue...

That is the right front shock, zip tie installed and car let down to sit at ride height, then raised back up for the picture.



It may be bottoming out. If not, it's getting close. But you'll know for sure after this weekend.

Regardless, it is something we'll need to address is your suspension upgrades.

[SSLance]

Shock travel measurements...

Was a busy day as I had to get the car ready for a co-driver to drive it first heat, then I was to drive it in heat 2, both of us were to get 5 runs each. I didn't do any measuring during Dan's runs in heat 1 as I was busy trying to get him used to the car then I took the opportunity to videotape his runs as I wanted some footage of the car on the track from the sidelines.

Here's a taste of that

http://youtu.be/Ya8ZOd5O76Q

Getting measurements on my front shock travel was next to impossible between runs as I could not only not see the bottom of the shock, much less measure in there...I was able to get my cell phone in there and get a pic of the ziptie after a run though. And it was as I figured, the zip tie was pushed down to the base of the shock.

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_133233_202-1.jpg

I verified this when I got it back home and on the lift, both zipties on the front shocks were bottomed out but not broken off or crushed. The front suspension pretty much lives on the stock bump stops, and I think the bump stops and the shocks bottom out at about the same point. The rubber cushion of the stock bump stop keeps it from being a hard stop though which makes it un-noticeable when driving, but it is clearly happening.

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_100435_708-1.jpg

The rear shocks work as intended from what I can tell. First off I had to take the backs loose to get the boots off of them and put the zip ties on. This let me feel the dampening on them when loose. I had to put my shoulder onto the bottom of the shock to push it back up and onto the shock mount when reinstalling...I was actually surprised at just how much pressure it took to push the shock back in.

I forgot my tape measure on the grid during my runs, but I did grab my phone and take pics of the rear shocks after each run, then pushed the zip tie back up again.

Left rear shock after run 2

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_130314_031-1.jpg

Left rear shock after run 3

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_131824_599-1.jpg

Left rear shock after run 4

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_133121_653-1.jpg



Right rear shock after run 2

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_124824_077-1.jpg

Right rear shock after run 3

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_131848_102-1.jpg

Right rear shock after run 4

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_133140_845-1.jpg


I know it's not exactly scientific, and I'll do better next time I promise.

I was having a few other issues at the same time that I was dealing with, one being this...

https://static1.pt-content.com/images/pt/2013/07/IMG_20130630_133702_102-1.jpg

This course design was heavy on fast left hand turns and fast long straights with lefthanders at the ends of them and it not only abused my brakes but also my right front tire...cutting my day a bit short. I decided to not try my fifth run and I wouldn't have bettered my time anyway as it was sliding the front pretty bad on my 4th run.

I HAVE to do something about my brake setup, it was a true weakness that this course design exposed big time. Several times under hard braking it wheel hopped the rears real bad...you just couldn't drive the car to it's potential because you had to back up the corners at the end of the straights so much.

Here is my best run from the side mount view.

http://youtu.be/8YhTlaVJOV4

If you watch in the carousel, you can tell it is sliding the fronts almost all the way through. Still a fun drive though.

[Ron Sutton]

Hi Lance,

*To keep anyone that is following along on the same page with us, Lance has not made any tuning changes yet. I asked him to get shock travel numbers to help us calculate suspension travels. Lance's next step is to measure all of the geometry points in his front suspension, so I can calculate his camber gain, roll centers, etc. Suspension travel numbers are helpful to figure out actual camber gain/loss & other things.

Shock travel measurements...

Was a busy day as I had to get the car ready for a co-driver to drive it first heat, then I was to drive it in heat 2, both of us were to get 5 runs each. I didn't do any measuring during Dan's runs in heat 1 as I was busy trying to get him used to the car then I took the opportunity to videotape his runs as I wanted some footage of the car on the track from the sidelines.

Here's a taste of that
At the 1:25 mark, you can clearly see the rear tire hop on corner entry under braking.

Getting measurements on my front shock travel was next to impossible between runs as I could not only not see the bottom of the shock, much less measure in there...I was able to get my cell phone in there and get a pic of the ziptie after a run though. And it was as I figured, the zip tie was pushed down to the base of the shock.
Even though we know the shocks are basically bottoming out, we still need the travel #. When you're back in the shop ... and push the zip ties up against the shock body ... and compare that to pushed all the way down ... you'll know the shock travel dimension for us.

I verified this when I got it back home and on the lift, both zipties on the front shocks were bottomed out but not broken off or crushed. The front suspension pretty much lives on the stock bump stops, and I think the bump stops and the shocks bottom out at about the same point. The rubber cushion of the stock bump stop keeps it from being a hard stop though which makes it un-noticeable when driving, but it is clearly happening.
Agreed, and not acceptable for your goals ... I think. I mean, using tunable bump stops on the shocks is the best cutting edge suspension set-up. But most people don't understand them & don't want to run bump stop style suspension set-ups.

You accidentally happen to have the A-arm bump stops touching at the right spot to not upset the car. So I am assuming you will want to correct this so we're not relying on the A-arm bump stops.

If we can get the front end to travel more, transferring more load & grip onto the front tires ... that will improve your cornering speeds. But ... and this is key ... you will need a bigger sway bar to control the roll. Right now, the bump stops are reducing the roll. :seizure:


The rear shocks work as intended from what I can tell. First off I had to take the backs loose to get the boots off of them and put the zip ties on. This let me feel the dampening on them when loose. I had to put my shoulder onto the bottom of the shock to push it back up and onto the shock mount when reinstalling...I was actually surprised at just how much pressure it took to push the shock back in.
Sounds a little stiff on compression valving. Good for turning ... not good for traction on corner exit. When you increase the spring rate in the rear, we may want to soften this valving.


I forgot my tape measure on the grid during my runs, but I did grab my phone and take pics of the rear shocks after each run, then pushed the zip tie back up again.
LOL. Rookie mistake, but I like photos.


Left rear shock after run 2

Left rear shock after run 3

Left rear shock after run 4
We can see the travels are not the same, which is unfortunately typical. The higher travel on different runs can be caused by either hitting a bump, or simply driven harder with more body roll. Only you can provide us with that feedback.


Right rear shock after run 2

Right rear shock after run 3

Right rear shock after run 4
Run 3 shows the most travel on the RR shock. Run 4 shows less, which is a good indicator the RF front tire was giving up. Anytime a tire .. or both tires ... are not gripping, body roll & pitch will be less. Other than hitting a bump ... it takes grip to produce body roll & suspension travel.


I know it's not exactly scientific, and I'll do better next time I promise.
Oh sure. Everyone says that. JK. :poke:

I was having a few other issues at the same time that I was dealing with, one being this...
That is a big ol' piece of proof that you car is over working the outside edge of the front tires, due to the KPI/Caster Split favoring the KPI so much.

This course design was heavy on fast left hand turns and fast long straights with lefthanders at the ends of them and it not only abused my brakes but also my right front tire...cutting my day a bit short. I decided to not try my fifth run and I wouldn't have bettered my time anyway as it was sliding the front pretty bad on my 4th run.
Good call. If you continued running hard ... the only thing you might have learned is how to get grass & cones off the under carriage.

I HAVE to do something about my brake setup, it was a true weakness that this course design exposed big time. Several times under hard braking it wheel hopped the rears real bad...you just couldn't drive the car to it's potential because you had to back up the corners at the end of the straights so much.
The "hopping" isn't a brake issue. You have too soft of a spring back there, and the shock can't control it.

*Lance sent me his brake system specs & I calculated his front, rear & total braking force. Which will be an upcoming topic for us.

Yes, you do need more front braking force & less rear braking bias. But the rear springs being so soft ... is the main culprit to the hop ... and also contributes to your mid corner push. More on this later.


Here is my best run from the side mount view.
A few observations & tips:
0:24 Keep the late apex, but increase your degree of turning to end up with a lower, straighter exit.*
0:36 Use more of the track. Let the car "eat" by running a larger, gentler, wider radius to the outside of the track on exit to carry more speed.
0:38 Straighten out this section ... to be closer when you clip by the inside edge ... then wider when you get to corner entry.
Cone Esses: You're a tick behind in your steering making you have to turn more.
1:03 Use more of the track. Let the car "eat" by running a larger, gentler, wider radius to the outside of the track on exit to carry more speed.
1:14 Keep the late apex, but increase your degree of turning to end up with a lower, straighter exit.*
*If the handling will let you.

If you watch in the carousel, you can tell it is sliding the fronts almost all the way through. Still a fun drive though.

Cool !


Was it really 75 degrees there? It was 108 here!

[SSLance]

Ron,

I've got planned to get the car on the lift here at the shop Wednesday morning after a car show tomorrow afternoon. I've got the part numbers of upper ball joints and hope to get them measured at the parts house on the way home tonight.





[COLOR="#0000FF"]A few observations & tips:
0:24 Keep the late apex, but increase your degree of turning to end up with a lower, straighter exit.*
0:36 Use more of the track. Let the car "eat" by running a larger, gentler, wider radius to the outside of the track on exit to carry more speed.
0:38 Straighten out this section ... to be closer when you clip by the inside edge ... then wider when you get to corner entry.
Cone Esses: You're a tick behind in your steering making you have to turn more.
1:03 Use more of the track. Let the car "eat" by running a larger, gentler, wider radius to the outside of the track on exit to carry more speed.
1:14 Keep the late apex, but increase your degree of turning to end up with a lower, straighter exit.*
*If the handling will let you.

If you watch in the carousel, you can tell it is sliding the fronts almost all the way through. Still a fun drive though.
[B]
Cool !


Was it really 75 degrees there? It was 108 here!


Thanks for the tips Ron. What I was really concentrating on was to find the line that got me through the tightest sections of the course with the least amount of steering input (knowing now how much more camber loss there is with the increased steering input).

For instance, during the pace lap I figured out that the large carousel near the beginning was just about the exact same radius the whole way around, so I found the line that got me through it all basically without moving the steering wheel at all once in the turn. I tried to control how it came out onto the next straight with the throttle not the steering wheel.

The run before was better in that section, but I really struggled with that next section finding the right braking spot to not leave too much time on the table while at the same time not wheel hopping under braking. I left some time leaving the carousel because I was thinking about how to set myself up for the end of the next straight.

I know I was behind every time in the esses, again I think it was because I'd upset the car before that first gate getting into them. In fact, I got scored with a DNF my first run (erroneously which they fixed after) because I went right at the first cone instead of left. I was about halfway thru the esses when I discovered that I was coming out pointed the wrong direction for the entry into the Chicago box (another rookie mistake).

#1 dealing with the hard braking zones and then #2 dealing with a going away right front tire really made for some less than satisfying runs for me. It was fun still the same, but I just wasn't getting the results I wanted.

And yes, it really was 75 degrees... Was a beautiful day for an autocross.

[Ron Sutton]

Ron,

And yes, it really was 75 degrees... Was a beautiful day for an autocross.

Aw man ... we were BAKING ! Still are. 5 days of 106+ temps.

[Ron Sutton]

Ron,

I've got planned to get the car on the lift here at the shop Wednesday morning after a car show tomorrow afternoon. I've got the part numbers of upper ball joints and hope to get them measured at the parts house on the way home tonight.

What about the lower ball joints?

[SSLance]

Lance, you need a Moog K5208 for the upper & Moog K6145 for the lower. Unless your DSE upper A-arms have a special ball joint in them. Call DSE & find out “for sure” as this is CRITCAL.


DSE says they use a Moog ANA5208 (same as the K5208?) in the arms I have...and I'm certain the lowers are just Moog factory replacements which I was planning on using the part number you provided above, Moog K6145.

[Ron Sutton]

DSE says they use a Moog ANA5208 (same as the K5208?) in the arms I have...and I'm certain the lowers are just Moog factory replacements which I was planning on using the part number you provided above, Moog K6145.

Okie Dokie. Just wanted to make sure you're finding the center & measuring both ball joints.

[Ron Sutton]

Lance,

I suggest you figure out what your scrub radius with your current set-up ... to help guide us on decisions about possible spindle KPI changes. If we see your current scrub radius in under an inch, it may be ok to change from your current spindles with 8.75 degrees KPI to a spindle with slightly smaller KPI .. like 8.0 degrees. On the other hand, if we see it is a couple inches or more ... and there are no plans to put wider wheels with more back spacing on ... we should stick with the 8.75 degrees.

As you know, I measure everything & work it out in a suspension software. But for the average car guy in his garage ... do this:

a. Determine the EXACT centerline height of your front spindle (Pick one ... left or right ... doesn't matter) ... with all 4 wheels & tires on the ground ... suspension loaded. It is going to be around 12-13". Let's say it is 12-3/4".

b. Remove that tire & wheel. Put a good, non-leaking jack under the the ball joint (or other secure point on the lower A-arm) & jack the spindle back to that exact same height ... in this example 12-3/4". (you are simulating ride height ... with 3 tires on the ground & a jack under one front corner.

c. Using a string, laser, straight edges or whatever works for you ... make a true line through the CENTERS of the upper & lower ball joints ... projecting onto the floor. Mark it. (I use blue 3M masking tape, so I'm not marking up my floor permanently.)

d. Ideally ... you want the mark on the shop floor to be more than a dot. What works best is a line 8-12" long TRULY PARALLEL with the car.

e. Put your tire & wheel back on ... and set the car on the ground.

f. Find the true centerline of your tire tread ... and measure the distance to the line you put on the floor. Whatever that measurement is ... in inches ... is your scrub radius. This method may not be dead on accurate ... but it'll be close enough to know what you're working with.

78317

Please post the Scrub Radius dimension, so I also know what we're working with.

[SSLance]

That shouldn't be that hard to do, can do it with the rest of the measuring when the time comes.

To figure the true centerline of the tire tread, maybe put a straight edge on the floor on the inside and outside of the tire, measure the distance front and back to make sure they are parallel then measure to find the center between them?

[SSLance]

No, it's not crucial for the lift to be exactly level. If the "floor" tilts more than 2-3 degrees, it may start to affect things, as the car will lean. Otherwise, you're just measuring height from "floor" to pivot points.

One tip though, and we do this when we are out at the track & can not make something level ... if you use a digital angle finder/level ... and learn your "floor" of the lift is 0.7 degrees to one side ... take that into account when & if you use a level to measure anything ... and set it at the 0.7 degrees the same direction.


I have two drive on lifts at work, one is pretty dern level both directions, the other is level side to side but the back of it is 3.5" lower than the front. This lift is MUCH easier for me to get access to. I have to move 2 cars and quite a bit of stuff to get access to the level lift.

I'm thinking about cutting 4 pieces of 4x4 posts and putting them under the back legs of the lift to get it much closer to level. Obviously if I didn't have to do this, it would save me more time for more accurate measuring.

Ron, what do you think I'll have trouble getting accurate measurements on if the back of the car is sitting 3.5" lower than the front but otherwise level side to side? Is that an issue that I would be better off dealing with?

The lift ramps are somewhat dirty, my plan is to cover the majority of the areas that will need reference marks made on them with duct tape as it's stickier and stronger. I plan to use strings with weights on each end to replicate the centerline of the car and the front tire centerline. This too should give me more time to concentrate on the rest of the measurements.

I'll spend the next couple of days getting everything in place and probably hit the actual measuring part on Saturday.

[Ron Sutton]

That shouldn't be that hard to do, can do it with the rest of the measuring when the time comes.

To figure the true centerline of the tire tread, maybe put a straight edge on the floor on the inside and outside of the tire, measure the distance front and back to make sure they are parallel then measure to find the center between them?

Yup. Make sure the tire is truly parallel with the chassis.

[Ron Sutton]

I have two drive on lifts at work, one is pretty dern level both directions, the other is level side to side but the back of it is 3.5" lower than the front. This lift is MUCH easier for me to get access to. I have to move 2 cars and quite a bit of stuff to get access to the level lift.

I'm thinking about cutting 4 pieces of 4x4 posts and putting them under the back legs of the lift to get it much closer to level. Obviously if I didn't have to do this, it would save me more time for more accurate measuring.

Ron, what do you think I'll have trouble getting accurate measurements on if the back of the car is sitting 3.5" lower than the front but otherwise level side to side? Is that an issue that I would be better off dealing with?
You don't want to have the car that far off. It will affect the actual ride height, making the front sit a little higher & the rear a little lower. Not accurate. I did not understand what you meant about leveling your lift with 4x4's ... and it's not critical I do ... but you need the car as level as possible.

The lift ramps are somewhat dirty, my plan is to cover the majority of the areas that will need reference marks made on them with duct tape as it's stickier and stronger. I plan to use strings with weights on each end to replicate the centerline of the car and the front tire centerline. This too should give me more time to concentrate on the rest of the measurements.
Sounds good.

I'll spend the next couple of days getting everything in place and probably hit the actual measuring part on Saturday.

Cool. if you have questions, just ask.

[Ron Sutton]

Hey Guys,

I'm on the Forum today for a few more hours ... then I'll be gone for a week.


I'm meeting up with my friend Neil Porter at Sears Point where he's running 2 formula cars in SCCA racing.

https://www.pro-touring.com/attachment.php?attachmentid=78694&d=1373072350



Then I'm camping with my girls the rest of the week.

https://www.pro-touring.com/attachment.php?attachmentid=78695&d=1373072681



I'll be back online late Thursday (7/11) or Friday morning (7/18).

[SSLance]

Well I think I have completed the measuring of all of the pivot points. What an interesting challenge. I learned a lot about my suspension geometry during the process even without the data back from Ron. There is no doubt in my mind now that the 28 year old rubber bushings in my passenger side lower control arm are compromised and the arm is now out of spec (which is probably a factor in my excessive tire wear on that side as well).

I've sent all of my measurements to Ron which I'm sure he'll compile into his spreadsheets when he gets back into town. Can't wait to see what he comes up with once he reviews the data I have given him.

Stay tuned...

[SSLance]

Here's how I went about accomplishing this exercise...first I had to create a worksheet to help me keep track of all of the measurements as I made them.

https://static1.pt-content.com/images/pt/2013/07/SuspensionPivotPointMappingWorksheet-1.jpg

Then I set the car on a level drive on lift in simulated race prep mode...I even put (1) BBC head on the floor in front of the driver's seat and (2) SBC heads behind the front seat to simulate driver's weight in the car. I then made a careful measurement of the spindle heights and removed the front tires and set bottle jacks under the A-Arms as close to the ball joints as I could get them and adjusted the screws in the bottle jacks to get the spindle heights at exactly the same height as they were with the front tires on. This allowed me much more room to make the measurements needed.

Here is the car on the lift with everything I used during the process set up and ready to go

https://static1.pt-content.com/images/pt/2013/07/DSC03043JPG-1.jpg

I needed to have a secure square stand for a laser level away from the car at different times and the shop press worked perfectly for this. Notice there is a laser level on the press pointed at the upper ball joint in this picture.

https://static1.pt-content.com/images/pt/2013/07/DSC03040JPG-1.jpg

I also used a laser level to light up the string running down the whole center of the car and another to light up the string exactly 10" in front of the spindle centerline.

https://static1.pt-content.com/images/pt/2013/07/DSC03041JPG-1.jpg

The framing squares and the magnets holding them in place were used in conjunction with the three laser levels, plumb bob, tape measure, digital caliper and verneer caliper to measure and record all of the pivot points from the three reference points of the center of the car, center of the spindle, and ride height, over 80 measurements in total including the track width and scrub radius measurements.

With a good friend's help, it took about a half day on Saturday, then a couple hours a night for 3 week nights to complete the process. I'm certain we could do it faster the next time given the tricks we learned doing this our first time.

But anyway, hopefully this shows the rest of you a bit more about what we had to go through to come up with all of the measurements that Ron is going to put to use to help me figure out a solution to my woes.

[Norm Peterson]

And does the camber gain on the inside tire happen at the same point that the camber loss on the outside tire happens?
I know I'm late here, but it's probably better to think of camber gain as a continuous curve over the entire range of suspension travel. It is not a constant value, although over short amounts of travel it won't vary a whole lot. This can be plotted in Excel once you generate a table of where the suspension pivots are located at various ride heights (I've got a 2-D model for the Malibu I used to have, and FWIW that car had ~640# front springs, ~165 rear springs, Bilsteins, F41 bars, and a little over -2.5° camber when autocrossed. Around +3° caster - it's been a few years so I don't remember it any closer than that).

Camber gained as a function of the angle you steer the wheels and caster & SAI is a separate animal.


Norm

[SSLance]

Hey Norm, good to see you in here.

For those that don't know, Norm helped me tremendously last season over on the Monte board when I was first trying to figure out how to autocross my car.

[SSLance]

Hey Ron,

When you get a chance, will you explain Roll Center in layman's terms please? In a general sense, how is a car's Roll Center calculated and how is this Roll Center used when tuning a front or rear suspension?

I hear or read of Roll Center referred to often in suspension discussions and I kind have a handle on it, I think...but with my new found clearer understanding of suspension geometry and your unique way of making details simple to understand, it couldn't hurt to go through this part of it one more time...for me and others as well.

Thanks,
Lance

[Ron Sutton]

Hey Ron,

When you get a chance, will you explain Roll Center in layman's terms please? In a general sense, how is a car's Roll Center calculated and how is this Roll Center used when tuning a front or rear suspension?

I hear or read of Roll Center referred to often in suspension discussions and I kind have a handle on it, I think...but with my new found clearer understanding of suspension geometry and your unique way of making details simple to understand, it couldn't hurt to go through this part of it one more time...for me and others as well.

Thanks,
Lance

Oh sure Lance,

I'll get right on that after I create peace in the Middle East. :seizure::banghead::screwy::poke::hah::hand:



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OK, seriously, I'm working on it now.

[Ron Sutton]

Hey Lance ... I wasn't able to create peace in the Middle East ... but I did write up some Roll Center info.

This may be my longest post yet ... and that's saying something. :attn:

I’ll be very basic for any readers following along that are completely new to this & apologize in advance for boring the veterans that already have knowledge of this. Cars have two roll centers … one as part of the front suspension & one as part of the rear suspension. I’ll first explain what role they play in the handling of a car … then how to calculate them … and finally how to tune with them.

Think of the front & rear roll centers as pivot points. When the car experiences body roll during cornering … everything above that pivot point rotates towards the outside of the corner … and everything below the pivot point rotates the opposite direction, towards the inside of the corner. Because the front & rear roll centers are often at different heights, the car rolls on different pivot points front & rear … “typically” higher in the rear & lower in the front.

If you were to draw a line parallel down the middle of the car connecting the two roll centers … this is called the roll axis … that line would represent the pivot angle the car rolls on … again “typically” higher in the rear & lower in the front.


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When a car is cornering … the forces that act on the car to make it roll … act upon the car’s Center of Gravity (CG). With typical production cars & “most” race cars, the CG is above the roll center … acting like a lever. The distance between the height of the CG & the height of each Roll Center is called the “Moment Arm.” Think of it a lever. The farther apart the CG & roll center are … the more leverage the CG has over the roll center to make the car roll. Excessive chassis roll angle is your enemy, because it is over working the outside tires & under utilizing the inside tires.

Some people like to look at the car as a unit. I look at it as two halves. Here are some examples … using a typical 3500# Pro Touring Car with 53% front weight… to provide more clarity:

If the CG is 20” high … and the front roll center is 2” below ground … the car has 53% of the 3500# weight with 22” of leverage to roll the front of the car.
If the CG is 20” high … and the rear roll center is 9” above ground … the car has 47% of the 3500# weight with 11” of leverage to roll the front of the car.
* Rolling the car that much more in the front overloads the outside front tire & under utilizes the inside front tire when cornering.

If you lowered the car 2” … the CG drops 2”. The front roll center probably moved too … but it’s not linear … as it is based on A-arm angles. Let’s say it dropped 1” in the front to 3” below ground and the rear stayed the same at 9”.

Now …
If the CG is 18” high … and the front roll center is 3” below ground … the car has 53% of the 3500# weight with 21” of leverage to roll the front of the car.
If the CG is 18” high … and the rear roll center is 9” above ground … the car has 47% of the 3500# weight with 9” of leverage to roll the front of the car.
* The front now rolls over less & the rear too, making the car run “flatter” … not flat, just less roll angle … working the inside tires better.

Any weight you can remove from high up … or relocate to lower in the car … moves the CG down … reducing the leverage it has over the roll center … allowing the car to have less roll angle during cornering … working all four tires more evenly … and the grip of four tires is faster than two. :)

We're not going to discuss CG further in this post. Of course it is important, but we'll assume it is somewhere in the 16"-22" range and just focus on roll centers. We’ll discuss moving the roll centers in the final section. But next, let’s cover how to figure out where your front & rear roll centers are at.

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Calculating the Front Roll Center:
Measuring all the pivot points in the front suspension to calculate the roll center in the front suspension of a double A-arm suspension car can be tedious … but the concept is quite simple.

Quick Acronyms:
UCA = Upper Control Arm
LCA = Lower Control Arm
BJC = Ball Joint Center
IC = Instant Center
RC = Roll Center
CG = Center of Gravity
CL = Centerline

Your UCA & LCA have pivot points on the chassis … and they pivot on the spindle at the BJC’s.
Forget the shape of the control arms … the pivots are all that matter.


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If you draw a line through the CL of the UCA pivots & another line though the CL of the LCA pivots … they will intersect at some point (as long as they are not parallel). That point is called the instant Center (IC) … and the UCA/Spindle/LCA assembly travels in an arc from that IC point. However far out that IC is … measured in inches … is called the Swing Arm length. More on this later.

Next you draw a line from the CL of the tire contact patch at ground level … to the IC. Do this on both sides … and where the two “Tire CL-to-IC” lines intersect … is the front roll center. Look at the drawing below. The colored dots represent the IC for the same color LCA/UCA. The black dot represents the static RC at ride height.

Make sense?


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Now I’ll throw you a curve ball. The static RC at ride height doesn’t mean much. It is the dynamic roll center “in dive” that really matters. “In dive” means when the front suspension is compressed & the car is in roll. So in the corner … after hard braking & turn in ... when you have the front suspension compressed & the car is rolled over … all those angles change … and therefore the roll center moves. It typically goes down … and may, or may not, migrate to the left or right of center. In the drawing below, the car is making a right hand corner … compressing the suspension 2” in the center and rolling over at a 3 degree angle.

Again, the colored dots represent the IC’s for the same color LCA/UCA. See how the IC’s move & the swing arm lengths change when the suspension is compressed & rolled? The black dot represents the dynamic RC in dive. Notice the RC is lower but also “migrated” to the left. (The software drawing is backwards, so the right side of the car is on the left, like if you were looking at the grill.)


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We’ll talk about how to tune with Roll Centers in the final section.

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Calculating the Rear Roll Center is MUCH Easier ...
Unless you have a double A-arm rear independent suspension … then it is exactly the same as the front.

For all other common rear suspension types, here are the quick methods.

Panhard Bar/Track Bar: The RC is located horizontally & vertically at the center of the two pivots. If the bar is level and both sides are 8” off the ground … the roll center is 8” above the ground. If the bar is at an angle with one side at 11” & the other at 12” … the RC is at 11-1/2”. (But this angle will make the car handle differently on LH & RH corners.)

The RC is located horizontally exactly in the center of the two panhard bar pivots … which is why it makes sense to have the bar centered in the chassis on street, road race & AutoX cars … so the RC is centered in the chassis. Some oval track cars use a J-bar, which is not centered horizontally, and therefore neither is the RC.

Watt’s Link: The RC is located horizontally & vertically at the center of the bell crank pivot that is attached to the rear end housing.

Leaf Springs: The RC is located horizontally in the center … halfway between the two sets of leaf springs. The RC is located vertically at the height equal to the mating line where the leaf spring connects to the housing spring pads. If lowering blocks are utilized, the RC height is in the center of the lowering blocks.

Triangulated 4-links: Draw a line connecting the IC of the lower set of trailing arms … to the upper set of trailing arms … and where that line crosses the axle CL … is the rear RC.

Diagonal Link: The RC is located horizontally & vertically at the center of the two pivots. If the diagonal link is centered, so will the RC be. If the diagonal link is at 6” on one side and 7” on the other … the RC height is at 6-1/2”.

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Tuning with Roll Centers:

First off, most people find tuning with the front roll center difficult, tedious, confusing & laborious … and therefore they don’t do it much. I love those people as competitors because they’re easy to beat. Getting fast … faster than everyone else … takes work, testing, work, smarts, more work & more testing. And the front suspension … which is the most complicated … is the most important key to cornering performance. Because I have studied, tested & worked on front geometry so much & now understand it so well, that has been to my advantage over the years.

You don’t have to become a tuner to have fun with your Pro Touring car. You can buy & install many good suspension packages available on the market that have a “much better than factory” set-up for your car … because the aftermarket manufacturer worked out a good basic geometry package. The car will handle well, outperform most factory cars and be a lot of fun. Just don’t disillusion yourself into thinking you’re going to show up at serious competitions & beat the “thinkers & tuners” with a bolt on package.

If running “good” isn’t good enough, and you want to compete at a higher level and win events … you need to learn about suspension geometry & tuning … and do lots of testing & tuning. I figure I have over 2500 test days under my belt in my 35 years of racing. I’m not the smartest guy at the track … but when he goes home … I’m still there testing, tuning, learning & getting faster. To win … you gotta be willing to do the work. If you’re not, be clear on that and set your goals accordingly. We’re all here for fun. Some of us find the fun of winning worth the effort & sacrifices it takes to do so.

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Tuning with Front Roll Centers:

Let’s start with the understanding that to move the front RC … you are changing the angles of the UCA and/or LCA … to achieve a different IC. Some changes affect RC only dynamically in dive … while most changes affect the RC both statically at ride height & in dive. I’ll put an * next to the item that only changes RC dynamically & doesn’t show up statically.

What are (or can be) your tuning tools to change angles:
1. Spindle heights and/or distances from spindle pin to ball joint surfaces
2. Ball joint pin heights
3. Control arm length*
4. Adjustable control arm mounts on the chassis.
5. Also, obviously, any changes in ride height.

Direction:
a. Raising the RC, places it closer to the CG, reducing the CG leverage, reducing roll angle … and working the front tires less.
b. Lowering the RC, places it farther from the CG, increasing the CG leverage, increasing roll angle … and working the front tires more.
c. For faster corners found at big road courses I’ve found the happy window to be 1” to 2.5” … and -0.5 to 1.0” for tight AutoX events.
d. If the RC migrates to the inside of the corner under dive … it will work the front tires more … but roll more if not controlled by the suspension.
e. If the RC migrates to the outside of the corner under dive … it will roll less work the front tires & roll less.

*KEY NOTE: For optimum cornering ability, you need to WORK the front tires … and a low front RC combined with a big front sway bar ... and either stiff rear springs or moderate rear springs & a significant rear sway bar ... works the front tires while keeping the roll angle low. In other words, don’t use the front RC as your primary tool to control the car’s roll angle.

For the hot rod I’m designing & building for myself, I have two front RC locations. For AutoX it is 0” in dive & 1.2” in dive for road racing & high speed events. All I have to do is change the slugs in two control arms & reset the toe & bump steer shim packet. Yes, I have big sway bars. :)

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Also know, when you are changing these control arm angles, you are changing the camber gain. Use this to your advantage.

A lot of stock production cars have the swing arms so far out … there is little to no camber gain … often camber loss. Plus, in many stock production cars the A-arm angles put the roll center so low it is below ground ... and the CG is high … giving it a ton of leverage to roll the car … which is part of why many stock production cars roll so much.


*KEY NOTE: Typically, when you dial in your front geometry … you’re goal is to place your RC for optimum handling for the type of driving you do (or find the best compromise) … and end up with the desired camber gain.

Some quick tips:
Anytime you’re shortening the “swing arm” … you’re increasing camber gain … regardless of how you did it.
Anytime you’re shortening the swing arm length … & keep the IC at the same height … you’re raising the RC.
Conversely, lengthening the swing arm length … & keeping the IC at the same height … lowers the RC.
Anytime you’re raising the IC of the swing arms … and keeping the same swing arm length … you’re raising the RC.
Conversely, lowering the IC of the swing arms… and keeping the same swing arm length … lowers the RC.

There are several software programs out there to calculate roll centers. I own & use several. I suggest Performance Trends to car guys & gals often because it is the easiest to use.

*KEY NOTE: When you change the swing arm IC … length or height … you are changing the bump steer … because you are changing the arc the UCA/Spindle/LCA assembly travels in. Another reason why so many people don’t like tuning on it.

For the hot rod I’m designing & building for myself, I have two front RC locations & have worked out the bump steer for both setups … which includes a tie rod slug & shims. I simply keep a “set” for each of the 2 RC locations, making the change over quicker & easy … after the initial work is done.

Last Key Note on Front Roll Centers
Once I have tested & worked out an optimum front end set-up for a type of track … we “lock it in” and don’t change it at the track. So this is NOT something you’re constantly tuning on … just initially. At the track, the optimum front end geometry is the optimum front end geometry … so as the track changes throughout the day … we’re tuning on other stuff to keep the car “balanced”.

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Tuning with Rear Roll Centers:

If you have a double A-arm independent rear suspension … then it is exactly the same as the front. Change the term from “spindle” to “upright” and party on. Everything else is the same.

For all other common rear suspension types, here are the quick methods to tune.

Panhard Bar/Track Bar: Each end has a rod end as a pivot point. In race cars, we use a variety of different styles of mounts on the chassis & housing that allow us to relocate these pivot points up or down on both sides. I see a lot of aftermarket suspension kits & frame clips that have no adjustability.

My first thought is “what the … @$&% !”

Then I realized they’re doing this so tuning rookies don’t get themselves in trouble. Frankly, I can not fathom not having the rear roll center adjustable. It is one of the most predictable tuning tools & with the right mounts, simple, quick & easy. It is so easy, that in racing circles, if a racer is “lazy” that’s the tuning tool they use first & most, which isn’t correct, just reality of human nature.

Watt’s Link: Very simple to move the bell crank pivot up or down, as long as there are holes available.

Leaf Springs: Do not have an adjustable RC unless you change the mounting points of the springs or use lowering blocks.

Triangulated 4-links: Do not have an adjustable RC unless you change the mounting points of the links. Great for street performance cars with owners not desiring to tune.

Diagonal Links: Are for drag racing … as they are not independently adjustable for RC in the typical mounting. They mount to the ends of the rod end bolts, so change only when the lower bars are being moved to different holes.

The two best methods of centering the rear end … and have tunability … are the Watt’s link & panhard bar. Many people favor a Watt’s link because it keeps the rear end perfectly centered during travel & roll. I like them, but they’re not my preferred method, because the method of mounting leads to limited adjustability … sometimes only a few holes … farther apart than I like to make changes … and often mounted with the RC too high for modern low roll suspensions.

This limited tunability of the Watt’s link requires the tuner to rely more on other tuning items such as springs, shocks & sway bars. It reminds me a little of torque arm suspensions. They work well, just not much tuning adjustment. I think they’re the ticket for car guys that want to get a good set-up & just drive it.

As a tuner, I like to have a full tuning “tool box” at my disposal, and a panhard bar (or track bar, depending on where you came from) is more tunable. With the right adjustable mounts, I can move the RC 1/16” if I wish. I can make it super low … super high … or anywhere in between.

If … for any variety of reasons … the car is working the rear tires different in RH corners versus LH corners … I can put a little “tilt” in the panhard bar … while keeping the same RC height … and even out how the car works the rear tires in RH & LH corners, making a more balanced, faster track car. Just lower the bar down on the side you want to work the tire more … and raise the bar up on the opposite side the same amount. If I’m at a road course where I need a “lil sumthin” extra in one corner, I can achieve that with a little panhard bar tilt.

As far as keeping the rear end centered … with the newer technology low roll suspensions … if the outside rear tire is compressing much more than an inch during cornering … I’ve got bigger problems than the rear end shifting a few thousandths off center.

Direction … regardless if you’re using a Watt’s link or panhard bar:
a. Raising the RC, places it closer to the CG, reducing the CG leverage, reducing roll angle … and working the rear tires less.
b. Lowering the RC, places it farther from the CG, increasing the CG leverage, increasing roll angle … and working the rear tires more.
c. With low roll suspensions utilizing mean stiff rear springs … or medium springs & significant rear sway bar … for faster corners found at big road courses I’ve found the happy window to be 9” to 12” … and 7” to 10” for tight AutoX events.
d. Softer sprung, higher roll rear suspensions run higher rear RC’s.

*KEY NOTE: For optimum cornering ability, you need to position the rear RC low enough to work the rear tires … allowing just enough rear roll angle to disengage the inside rear tire to a degree … but high enough to prevent the outside rear suspension from compressing so much that the car rolls diagonally … and unloads the inside front tire.

Old school, conventional, soft sprung rear suspensions achieve this with higher rear RC’s. Modern low roll suspensions achieve this with stiff rear springs (or or medium springs & significant rear sway bar) to control the roll angle, while utilizing a lower RC to work the outside tire more. In other words, modern suspensions don’t use the rear RC as the primary tool to control the car’s roll angle.

For the hot rod I’m designing & building for myself, I have two rear baseline RC locations. For AutoX it is 8” & for road racing & high speed events it is 11”. Because both sides adjust easy, it is about a 2 minute change. :)

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Whew! That's all for now.

[instro84]

Ron, thats alot to take in. good info gave me some insight all the cars i've built in the past were for straight line performance. thanks for the info.
dale

[SSLance]

See, I knew you could do it Ron. :twothumbs Seriously...that is exactly what I was looking for when I asked the question. Thanks...

For the rest of the class, Ron has shown me the initial results of the diagrams like above using the measurements from my car and while digesting those, I was a bit lost in exactly what I was looking at, especially in regards to roll center. I figured best thing to do was ask and let Ron explain it to all of us in his own special way.

It is unbelievable to me how Ron can take something so complex and with words and a few pictures describe it in a way that makes it easy to understand. That is SO cool. :hail:

[Ron Sutton]

See, I knew you could do it Ron. :twothumbs Seriously...that is exactly what I was looking for when I asked the question. Thanks...

For the rest of the class, Ron has shown me the initial results of the diagrams like above using the measurements from my car and while digesting those, I was a bit lost in exactly what I was looking at, especially in regards to roll center. I figured best thing to do was ask and let Ron explain it to all of us in his own special way.

It is unbelievable to me how Ron can take something so complex and with words and a few pictures describe it in a way that makes it easy to understand. That is SO cool. :hail:

Hi Lance, Thanks for the kind words.

Explaining what roll centers are, how to calculate them & how to tune with them ... front & rear ... was a little easier than creating peace in the Middle East, but not by much.
:rolleyes:

That post got into the detail of roll centers (RC) ... but I think it's helpful for car guys & tuners to take several steps back & look at the big picture of handling ... to better understand the role of the RC with the rest of the car.

Total weight ... weight distribution front to rear ... and height of this weight (CG) act like a lever over the roll center. As discussed earlier, lowering the CG shortens that lever, as does raising the RC ... but works the tires less. Raising the CG lengthens that lever, as does lowering the RC ... and works the tires more.

Your goal is to move them both ... to the degree possible ... where you find the optimum balance of working the tires & roll angle. BUT ... and this is KEY ... modern day tuners do not use the RC height as the primary means of controlling roll angle. They use the suspension tuning items as their primary tools & the RC height as a secondary tool.

So to achieve the optimum balance of roll angle & working the 4 tires optimally ... this all has to work with your suspension ... springs, anti-roll bars & shocks ... and track width ... to end up at the optimum roll angle for your car & track application.

Hopefully, this brief overview, helps clarify roll centers place in the tuning picture.

[Ron Sutton]

Hey everyone,

If you're following along with Lance's project, he measured & re-measured all of the suspension points on his '85 Monte Carlo SS. He learned several things during the process.

1. Measuring this stuff accurately is tedious & time consuming.
2. He found some issues with his car that we will correct along the way.

I use several programs to work out Roll Centers, camber gain, etc. The Performance Trends oval track software is the quickest & easiest, and nothing about it limits it to oval track use.

NOTE: Everything on the screen is BACKWARDS, like you're looking at the car's grill head on. So the driver's side is on the right side of the screen & the passenger side is on the left side of the screen. Another tip, are the dots, lines & numbers are color coded by side. Red is the right/driver side. Blue is left/passenger side. The Black dot is the roll center.

This first screen shot represents car sitting at ride height.
Pay attention to some differences in the left side measurements & right side measurements. Then notice the roll center is not centered. These differences are the reason why.

Other things to note are:
* The Instant Centers of the left & right A-arm assemblies form different "swing arm" lengths. This is the actual cause of the roll center being 9.3" to the left.

* These swing arm differences will compound with body/chassis roll.

* While it doesn't show on this screen. The right side LCA is tipped "up" in the front on Lance's car, causing the right LCA to have a different angle that affects dynamic caster & anti-dive on that side. On this screen it just shows the "average" right side lower frame pivot as being higher than the "average" left side.
(The individual control arm measurements are actually input on a different screen. )

* The static roll center ends up below ground. This is somewhat common on factory passenger cars. Combine this with high CG's & soft suspensions & the reason why production cars have so much body roll is clear.


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In this next screen shot, we have the car showing a "freeze frame" of the dynamic geometry ... when the car is making a hard right hand corner at the AutoX track.

Things to note are:
* In the lower right hand corner, we're showing the front suspension compression & car roll angle. Shock travel on this car is low at .8" & roll angle is high at 3 degrees.

* The dynamic roll center has moved farther underground than it was statically at ride height, contributing to the high roll angle.

* The dynamic roll center has "migrated" 12.4" to the right ... ending up 3.1" to the right of center ... which contributes a small degree to body/chassis roll angle on RH corners.

* The dynamic camber goes way negative on the inside tire (bad) & positive on the outside tire (bad). (This does not account for KPI & Caster with the steering turned)


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In this final screen shot, we have the car showing a "freeze frame" of the dynamic geometry ... when the car is making a hard left hand corner at the AutoX track.

Things to note are:

* The dynamic roll center is not as far underground as it was in right hand turns or statically at ride height. This difference is contributing to the car handling different in LH & RH turns.

* The dynamic roll center has "migrated" to 18.7" to the left of center ... which contributes a high degree to body/chassis roll angle on LH corners.


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These are things that should and can be corrected. They corrections are not a 'bolt-on". I'll guide Lance on how to fix these issues when we install new LCAs.

Plus, we're going to install longer lower ball joints ... changing the angle of the LCA's ... and moving the geometry to achieve a roll center a little above ground statically & near ground level (zero) in dive.


.

[SSLance]

Thanks Ron for the clear and concise explanation of what's going on with my car.

Here's a snip from the very first post in this thread...and the reason I started it to begin with.



I ran my GoPro behind all four tires over the weekend, the back tires on Saturday during the test n tune session and the fronts on my first two runs of Event 1 on Sunday.

Here's the video of all of them.

http://youtu.be/idpMHtBwAm4

At about 1:58 in, you will notice that my right rear tire starts chattering and the rear looses traction. This happened with some regularity all weekend long, and it only does it on left hand turns...the back actually feels real good on right handers. I've got the front sorted out pretty well too, as long as I get it braked and settled before turning it, the front sticks pretty good.


Well, that was back in April and I've learned SO much more about all of this and my car since then. Thanks to all of you that have helped me understand what is going on and a great big thanks to Ron for prodding me along a somewhat difficult process...aimed at not only figuring it out, but then finding a fix for what ails it.

It is interesting to me that I thought I'd be chasing a rear suspension demon, when most likely what's going on up front was causing the symptom in the back I was asking about.

I can't wait to start the fixing part of it now. It might end up being just a bit more complicated than just bolting on new LCAs and heading to the alignment shop, but I'm also more capable at understanding this stuff now...so I feel ready for the challenge.

[CornerCarver]

Ron this info is invaluable, keep it coming!! As stated by others before you have a way of putting these things so anyone can understand them, I have a pretty good handle on most mechanical things and you have made soaking this up MUCH easier I am sure. I can't wait to put some of these things to use on my Monte this winter! Thanks!

Lance, I can't wait to see this thing run after you finish all of these changes!! It's going to be awesome I'm sure. You think you'll make next weekend?

[Norm Peterson]

Lance - pay attention to what the pavement looks like when you get into the tire chatter. It looked pretty consistent with encountering rain-grooved pavement from here. I'm not sure how that might affect the path to solution, but if you could somehow get similar video on pavement that is not rain-grooved I think it'd help.


Norm

[SSLance]

Norm, our normal course is all smooth asphalt straights and grooved concrete patches in between them connecting them all. Almost every tight turn we make during an autocross is going to encounter grooved concrete at some point. What is certainly noticeable though is how the car reacts so much differently on the left handers than the right handers. I also notice it in the slaloms which are almost always strictly on asphalt.

[Norm Peterson]

OK. That was something that kind of jumped out at me quite frequently in the video, and I really just wanted to see it eliminated as potentially being a primary cause.


Norm

[Ron Sutton]

OK. That was something that kind of jumped out at me quite frequently in the video, and I really just wanted to see it eliminated as potentially being a primary cause.

Norm

Hi Norm,

Are you referring to the grooved concrete as the primary cause of the front end push or the rear wheel hop?

[Norm Peterson]

Hi Ron,

Not necessarily a primary cause.

I see it as something that causes the local tire loading at the very outer edges of the contact patches to vary a little depending on whether it's a ridge or a groove that's underneath there, and this might be clouding the picture a bit. Tire size vs wheel width may even be involved with this.

I do know that kind of road surface sure feels different ("woozy") to drive over even when you aren't driving hard. Only one car/wheel/tire combination I've ever had might not have felt like that.


Norm

[SSLance]

Norm you might not have seen this yet, This post is from the negative camber thread at MCSS from last year...had to go looking for it after the new discoveries.






I'm also having a bit of difficulty visualizing how the rear cambers could be significantly different, although the difference would tend to explain the greater sensitivity to throttle in left turns that I think I'm seeing in the various videos. Second cup of coffee isn't helping, either.


Norm


You know, now that you mention that, the car is way more sensitive to loosing the back in left hand turns vs right handers...

Can that small of a difference in rear camber, rear toe, or weight differences really make that much of a difference in left turns and right turns?

And if the rear axle tubes weren't welded perfectly straight onto the center section, and that created the camber difference between sides...how would changing the front settings change that rear camber?

I'm also curious how making very small changes on the front of this car, can affect the rear toe?




What I know now is...yes the axle tubes are not perfectly straight on my rear axle, that is a fish to fry another day. But the real culprit to the uneven feeling in the turns is in the position of the passenger side front LCA.

Almost a year later...

[SSLance]

I should probably update this to add...do not use this method of setting your car up for measuring.





I then made a careful measurement of the spindle heights and removed the front tires and set bottle jacks under the A-Arms as close to the ball joints as I could get them and adjusted the screws in the bottle jacks to get the spindle heights at exactly the same height as they were with the front tires on. This allowed me much more room to make the measurements needed.

https://static1.pt-content.com/images/pt/2013/07/DSC03043JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/07/DSC03040JPG-1.jpg


Ron entered the numbers I gave him after the initial measuring using this method, then got back to me to go over some discrepancies...things weren't adding up. So I put the car back on the front tires on the rack and remeasured all of the height numbers...and they were all quite different.

I'm guessing the bottle jacks kept the suspension from settling completely like it will when sitting on the tires themselves. Was a nice try I thought, but in action, did not work as hoped. Part of the learning experience I guess.

Eventually I plan on fabbing up or purchasing some steel plates to bolt onto the hubs that will extend down to the ramp to set the hub at ride height. They'll have to be a bit adjustable height wise and also be able to slide around a bit once on the ground surface to allow the suspension to settle completely. What they will do though is not only allow more access for pivot point measuring, but also provide a nice flat base to measure from for setting alignment specs once changes have been made. One or two trips to the alignment shop saved should more than pay for the stands I believe.

[Ron Sutton]

Hi Ron,

Not necessarily a primary cause.

I see it as something that causes the local tire loading at the very outer edges of the contact patches to vary a little depending on whether it's a ridge or a groove that's underneath there
Absolutely.

, and this might be clouding the picture a bit.
No clouds. All clear.

Tire size vs wheel width may even be involved with this.
I concur, if the tire was on a wider rim, with more psi, the situation would be lessened.

I do know that kind of road surface sure feels different ("woozy") to drive over even when you aren't driving hard. Only one car/wheel/tire combination I've ever had might not have felt like that.

Norm

In the front, the tires push on both surfaces when turned far enough. The front end geometry & excessive body roll are causing the outside tire to go into positive dynamic camber & the inside tire to go into negative camber. Lance's helpful video provided insight & started on us on this working relationship. The tire loosing contact patch is the primary cause of the push. When it happens on the grooved concrete, it obviously adds another dynamic to the tires.

On pavement, the rear tires get a little "bound up" when the front tires go into a push condition, but are not snapping loose in this situation. The oscillations initiated from the grooved concrete are causing the rear tires to loose grip in that section, making the car momentarily loose, until Lance counter steers & it "catches".

The rear springs being too soft of rate & older shocks with weak valving are not able to control it. The soft rear springs ... combined with his rear sway bar & roll center ... are also contributing to his push condition ... as the car is not rolling equally or balanced.

During cornering, the suspension is traveling much farther in the rear than the front ... more than twice as much. As you probably know, when that happens, the car rolls diagonally ... working the outside rear tire more (increasing rear grip) and working the inside front tire less (decreasing front grip). This issue is simply compounding the push issue ... as is the uneven surface of the grooved concrete.

Lance & I are focused on both ends of the car ... with plans to travel the front end farther ... travel the rear end less ... and roll less. But first, we're working on steering geometry to correct the dynamic wheel angles to maximize front tire contact patch.

[Norm Peterson]

Norm you might not have seen this yet, This post is from the negative camber thread at MCSS from last year...had to go looking for it after the new discoveries.
I chased it down, and I'm still trying to wrap my head around the "cross" being so much. Particularly when the 'before' cross was 0.3° smaller - it's still too easy to blame alignment setup error/shift. Otherwise I'm looking for almost a visible kink in the left side axle tube midway-ish out between the pumpkin and the axle end . . . like maybe under the left rear spring?

But anyway, all of those rear cambers are less than the amount the axle rolls due to the differences in tire compression from load transfer, and the right side will go further positive than the left at the same lateral g, so it still sounds more left turn sensitive no matter which set of rear camber numbers you care to use for this anyway.


Norm

[SSLance]

I think the "problem" has been there all along, to one degree or another. Through all of the changes I've made so far, the car has always handled differently turning left than when turning right. I've just had to adjust my driving style to fit it, never really knew what the cause was. The side to side differences I found in the frame mounting points of the front LCAs along with the resulting different positions the lower ball joints are in side to side were what Ron and the software used to come to the conclusions he posted above.

Just one example showed when I put the DSE front UCAs on last summer, at the alignment shop we didn't have enough stud on the passenger side frame mounts to get the caster to the same point as we had on the driver's side, while retaining the same camber setting...we had to put the offset slugs in the cross bar on the passenger side only to get the two sides close to even.

What is amazing to me is how little the differences are at the mounting points, yet how much they affect the actions of the spindle\ball joints out at the other end of the control arms, and how those actions affect things like Roll Center the amount they do.

[Norm Peterson]

The rear springs being too soft of rate & older shocks with weak valving are not able to control it. The soft rear springs ... combined with his rear sway bar & roll center ... are also contributing to his push condition ... as the car is not rolling equally or balanced.
The shock issue is interesting. My understanding of the IAS shocks is that they can differentiate on their rebound side between the chassis moving upward as in roll and the wheel moving downward as into a pothole, and apply different amounts of damping using a Ricor valve (some sort of inertia valve) like a hydraulic switch.

I wonder how badly the inertia valves are getting confused by the combination of chassis-up due to roll plus the up/down of wheel chatter. In that scenario, does the valve allow "full" fluid bypass through the piston, some bypass, or none at all? I suspect that once roll is essentially fully developed that the valve might be migrating to somewhere in the middle of its travel, doing a little chattering of its own there, bypassing at least some fluid, and generally behaving like a tired conventional shock. And it would still pass a static-ish "bounce test" just fine.


Got it on the rest.


Norm

[Norm Peterson]

I think the "problem" has been there all along, to one degree or another. Through all of the changes I've made so far, the car has always handled differently turning left than when turning right. I've just had to adjust my driving style to fit it, never really knew what the cause was.
Makes sense that the better you get as a driver, the more these little things get noticed.



The side to side differences I found in the frame mounting points of the front LCAs along with the resulting different positions the lower ball joints are in side to side were what Ron and the software used to come to the conclusions he posted above.

Just one example showed when I put the DSE front UCAs on last summer, at the alignment shop we didn't have enough stud on the passenger side frame mounts to get the caster to the same point as we had on the driver's side, while retaining the same camber setting
Don't you just love "factory tolerances"?


...we had to put the offset slugs in the cross bar on the passenger side only to get the two sides close to even.
Bet it was at the rear shim pack and involved a header tube. At my autocross alignment I got awfully close to running out of threads there as well.


What is amazing to me is how little the differences are at the mounting points, yet how much they affect the actions of the spindle\ball joints out at the other end of the control arms, and how those actions affect things like Roll Center the amount they do.
I think you'd have to be the suspension's original designer/engineer to be ably to look at a sheet of numbers and instantly know what they all meant. Or somebody of equal or higher talent. For the rest of us, it's a matter of actually running the numbers and looking at the plots that makes it make sense. Ergo, Performance Trends and other commercially available softwares in Ron's case and spreadsheets in mine (never could get the Perf Trends demo to work on my computer, so I wasn't about to throw any money at it).


Norm

[Ron Sutton]

The shock issue is interesting. My understanding of the IAS shocks is that they can differentiate on their rebound side between the chassis moving upward as in roll and the wheel moving downward as into a pothole, and apply different amounts of damping using a Ricor valve (some sort of inertia valve) like a hydraulic switch.

I wonder how badly the inertia valves are getting confused by the combination of chassis-up due to roll plus the up/down of wheel chatter. In that scenario, does the valve allow "full" fluid bypass through the piston, some bypass, or none at all? I suspect that once roll is essentially fully developed that the valve might be migrating to somewhere in the middle of its travel, doing a little chattering of its own there, bypassing at least some fluid, and generally behaving like a tired conventional shock. And it would still pass a static-ish "bounce test" just fine.

Got it on the rest.


Norm

Although I know a guy that worked for Edelbrock valving shocks ... I am not familiar with that shock design feature, so it's outside my wheel house. I can tell the valving is weak & the shock is not controlling the wheel when I watched the video.

Since the shocks are old, one of the changes Lance is planning in the future will be purchasing shocks, instead of revalving these. I will suggest a valving curve for the new shocks to go along with the suspension strategy he decides on.

But all these changes take money ... Lance's money :lol: ... so we're on the same page that the improvement of his Monte Carlo will take time & be done in steps.

Please stay with us as we make these steps.

.

[Norm Peterson]

I'd specifically looked into them myself quite a few years ago. On the surface, it sounded like a good concept, so I did my research on them and ultimately decided against them. Can't remember exactly why any longer, only that it was with less well developed reasoning than what I posted above (because back then I knew even less about shocks). FWIW, I ended up getting Bilsteins, with the front shock part number being for the S10 and assumed to be a better match for the 640# springs.


I know - it can be awfully easy to spend somebody else's money.


Norm

[SSLance]

Well, we made a pretty good jump on spending some of Lance's money this week. :naughty:

Phase one parts have been ordered, now we are just waiting in parts jail for all of them to come in. I'll document what we ordered and the installation process once they all get here. Should be a pretty major difference in geometry and setup once they are all installed.

One of the parts Ron suggested was a much bigger sway bar for the front...he says once we get the front suspension traveling again, it will be much needed. A popular upgrade for these cars is a 36 mm bar from a 3rd Gen Camaro...and I found one this week locally so I cleaned it up, painted it and went ahead and installed it today.

From just a short road trip to the car wash and back, I can tell a difference already. Turn in seems much more crisp and the car definitely stays flatter. Tomorrow will be the real test though as our SCCA Solo Event 8 is scheduled. The car is prepped and on the trailer, can't wait to get back out there.

[Mizzouri]

Lance, I had a blast riding along for yesterday's autocross. You're going to be giving me serious fits by next season!

P.S. I call dibs on another ride once you get the rest of the parts installed.

[SSLance]

No problem, as you can tell I have a blast out there just driving...even more fun to share it with a passenger.

So I wanted to do some before and after suspension cam shots, yesterday was the before...

http://youtu.be/FqR2GJ1LPM0

I couldn't find a suitable spot in the back to put the camera to get any rear suspension shots, I'll work on that before the next autocross in two weeks. The bigger bar up front really helped the front stick and kept the car flatter in the corners. It'll be interesting to see what if any still shots our photographer grabbed of the car in the corners and if it looks any flatter. Seat of the pants told me it was significant though.



Meanwhile, the first box of new parts showed up today...

https://static1.pt-content.com/images/pt/2013/07/IMG_20130729_103258_098-1.jpg

I'll go over all of them in detail once they all show up. Stay tuned...

[Ron Sutton]

Well, we made a pretty good jump on spending some of Lance's money this week. :naughty:


Yes we did spend some of your money. Not a ton ... but hey ... there's still time.

In a PM, I proposed to Lance the following changes:
A. New LCA's that move the lower ball joint forward for more caster ... and replaces the worn out bushings in his stock LCAs with poly
B. Taller lower ball joints to move the roll center as outlined in the coming graphs ... and increase camber gain. :)
C. Raise the car 1" front & rear ... to increase travel.
D. Bigger front sway bar.
E. Stiffer rear springs
F. Adjusters for all 4 springs to adjust ride height & corner weights.
G. Tie rod kit with spindles studs to correct bump steer.
H. Modifying & correcting the pivot angle of passenger side LCA.
I. Adding additional caster with LCA pivot modifications on both sides.

I ran some new calcs with raising the car 1" and adding the 3/4" taller lower BJ's & like the set-up. I've attached the graphs. It creates a powerful migration of the roll center to the inside of each corner (evenly).

Parts are starting to arrive & there is a lot of work to do. But the good news is Lance has to do all the work & I get to drink beer in the air conditioning while I wait on photos & updates. :rotfl: :cheers:

Here is the new front end geometry with corrections, ride height change & taller lower BJ's. The 2nd one is making RH turns & the 3rd one is making LH turns. Yes, I designed it to migrate the roll center that far & that direction.

Reminder: The illustration is backwards, like your looking at the grill. The passenger side is on the left.


This is at ride height.

80048


This is "in dive" suspension compress, body rolled & making RH turns.

80049


This is "in dive" suspension compress, body rolled & making LH turns.

80050

.

[Ron Sutton]

Hey Lance,

Is this you when the delivery guy shows up each day with new parts?

:twothumbs: :woot: :bananna2: :cool: :yeah: :jump:

[SSLance]

It's like Christmas in July...over and over and over again...


80072 80074 80076 80078

[SSLance]

So the parts are rolling in and phase 1 of the transformation is underway. I did the 36 MM sway bar swap up front last weekend and this weekend I'll do the spring upgrade in the rear.

Here are some pictures of the new rear springs and spring height adjusters. The springs have a 2.5" pigtail on one end and a 4.375" ID on the other. The adjuster flange has a 3.5" OD the spring sets on. My friend John turned a set of spacers for me to make sure the big end of the spring stays centered on the adjuster.

https://static1.pt-content.com/images/pt/2013/08/DSC03111JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03112JPG-1.jpg


Here is a picture of one of the adjusters set over the spud on the chassis the top of the rear spring rides on.


https://static1.pt-content.com/images/pt/2013/08/IMG_20130730_184652_981-1.jpg

The DSE front springs that I am going to reuse have a 4.063" ID so John also made me a pair of spacers for the front adjusters.

https://static1.pt-content.com/images/pt/2013/08/DSC03114JPG-1.jpg


The adjusters offer 2" of range, from a 1/2" to 2 1/2"


https://static1.pt-content.com/images/pt/2013/08/DSC03116JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03117JPG-1.jpg


What gets me is these adjusters and springs cost about half as much as any off the shelf drop springs sold for these cars. Just think of how many of these cars have had springs changed out over and over again trying to get the spring rate and ride height where the owner wanted it... Doesn't this make a WHOLE lot more sense?

Once I test fit everything, I'll decide if the adjuster will go on top of the spring or on the bottom, whichever it fits better on and gives the easiest access to is what I'll use. I think I'm going to drill a couple of holes in the adjuster flange and rosette weld the spacers to the flange to make sure they stay in place. On the big one for the rears, I can probably drill and tap it to run a screw into place but the small one for the fronts there probably isn't enough meat there for that. Heck, the spacers might not even be needed for the fronts, but they are there just in case.

If everything goes smooth, I should have the rear springs mounted, adjusted and in place on Saturday. I then plan on putting the street wheels and tires back on the car and running our next SCCA event on Aug. 11th where I'll put the GoPro on each of the four wheels per run. This will give an apples to apples comparison to the video I did at the beginning of this thread, only with the sway bar upgrade up front and the stiffer springs upgrade in the rear.

Then after that event, I'll start on the lower control arm upgrade up front which will be a bit more involved.

[rustomatic]

Thanks to Ron for turning me toward this thread (I read some before, but not up to date). It's funny how measuring things really starts you down the path of never getting done; it's also funny how it moves you toward improvements that you'd never even considered (or possibly thought possible).

It's astounding how much body roll occurred in my archaic (yet effective) suspension design on the Falcon after putting bearings in all of the pivot points (short of the sway bar); the original design had bind that both limited and greatly slowed down suspension travel, which in many ways does not actually promote "safe" handling. In one way, I win as a result of my adjustable strut rods, since I can dial in more caster when the UCA angles start to get a bit scary (soon).

I can feel the pain of dealing with front and rear suspensions at the same time, and I'll look forward to the changes of spring rate and roll center ideas as applied to Lance's car. I recently softened my own rear springs, and have somewhat lapsed on my Panhard adjustments in the face of many other changes I've recently made.

Not that I'd know, but it seems like the idea of trying to balance the front with the rear will not be unlike trying to figure out how to live with kids...

As a final thought, are the lower ball joints like K772s? Will camber gain really be greater with the LCAs starting from more of a parallel position (from the taller BJs), as opposed to the previously inverted situation (mine are somewhat inverted, due to ride height)?

What rear spring rates are on the Lance-mobile? Is there a Panhard, and if so, does it adjust on both sides?

[Ron Sutton]

Thanks to Ron for turning me toward this thread (I read some before, but not up to date). It's funny how measuring things really starts you down the path of never getting done; it's also funny how it moves you toward improvements that you'd never even considered (or possibly thought possible).

It's astounding how much body roll occurred in my archaic (yet effective) suspension design on the Falcon after putting bearings in all of the pivot points (short of the sway bar); the original design had bind that both limited and greatly slowed down suspension travel, which in many ways does not actually promote "safe" handling. In one way, I win as a result of my adjustable strut rods, since I can dial in more caster when the UCA angles start to get a bit scary (soon).

I can feel the pain of dealing with front and rear suspensions at the same time, and I'll look forward to the changes of spring rate and roll center ideas as applied to Lance's car. I recently softened my own rear springs, and have somewhat lapsed on my Panhard adjustments in the face of many other changes I've recently made.

Not that I'd know, but it seems like the idea of trying to balance the front with the rear will not be unlike trying to figure out how to live with kids...
OMG ... that's funny !!! :rotfl: :rotfl: :rotfl:


As a final thought, are the lower ball joints like K772s?
Same style ball joint as stock ... press in & GM taper. But with 3/4" taller pins & SD strong housings from Howe


Will camber gain really be greater with the LCAs starting from more of a parallel position (from the taller BJs), as opposed to the previously inverted situation (mine are somewhat inverted, due to ride height)?
See answer below.

What rear spring rates are on the Lance-mobile? Is there a Panhard, and if so, does it adjust on both sides?


No panhard bar. Stock Monte Carlo triangulated 4-link. We'll post spring rates & sway bar sizes soon.

Antime you are changing control arm angles, you are changing the camber gain. Use this to your advantage.

A lot of stock production cars have the swing arms so far out … there is little to no camber gain … often camber loss. Plus, in many stock production cars the A-arm angles put the roll center so low it is below ground ... and the CG is high … giving it a ton of leverage to roll the car … which is part of why many stock production cars roll so much.

Typically, when you dial in your front geometry … you’re goal is to place your RC for optimum handling for the type of driving you do (or find the best compromise) … and end up with the desired camber gain.

Some quick tips:
• Anytime you’re shortening the “swing arm” … you’re increasing camber gain … regardless of how you did it.
• Anytime you’re shortening the swing arm length … & keep the IC at the same height … you’re raising the RC.
• Conversely, lengthening the swing arm length … & keeping the IC at the same height … lowers the RC.
• Anytime you’re raising the IC of the swing arms … and keeping the same swing arm length … you’re raising the RC.
• Conversely, lowering the IC of the swing arms… and keeping the same swing arm length … lowers the RC.

[SSLance]

It's funny how measuring things really starts you down the path of never getting done; it's also funny how it moves you toward improvements that you'd never even considered (or possibly thought possible).


The measuring taught me things about this particular car that blew my mind. It also made things ever so much clearer for me. Hopefully the never getting done part doesn't come true though. My OCD leads me down a path that over analyses everything, plans as much as possible out beforehand and drives me to not stop until I see the plan through completion.


Not that I'd know, but it seems like the idea of trying to balance the front with the rear will not be unlike trying to figure out how to live with kids...

I wouldn't know either...unless you consider the four legged kind. Hopefully it's just less expensive than college tuition though.




More Parts Porn...

80261

80262

80263

80264

80265

[Ron Sutton]

Purdy stuff. :)

[diesel25lrs]

Lance,

Curious how did you do it when you went back and measured again without the bottle jacks to get suspension at ride height?


I should probably update this to add...do not use this method of setting your car up for measuring.






https://static1.pt-content.com/images/pt/2013/07/DSC03043JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/07/DSC03040JPG-1.jpg


Ron entered the numbers I gave him after the initial measuring using this method, then got back to me to go over some discrepancies...things weren't adding up. So I put the car back on the front tires on the rack and remeasured all of the height numbers...and they were all quite different.

I'm guessing the bottle jacks kept the suspension from settling completely like it will when sitting on the tires themselves. Was a nice try I thought, but in action, did not work as hoped. Part of the learning experience I guess.

Eventually I plan on fabbing up or purchasing some steel plates to bolt onto the hubs that will extend down to the ramp to set the hub at ride height. They'll have to be a bit adjustable height wise and also be able to slide around a bit once on the ground surface to allow the suspension to settle completely. What they will do though is not only allow more access for pivot point measuring, but also provide a nice flat base to measure from for setting alignment specs once changes have been made. One or two trips to the alignment shop saved should more than pay for the stands I believe.

[SSLance]

Lance,

Curious how did you do it when you went back and measured again without the bottle jacks to get suspension at ride height?

After putting the car back down on the tires, I just had to get more creative with where and how I placed the laser levels to get the measurements from. Using the framing square with welding magnets to hold it true and square helped a lot to get into the tight spots.

Plus I wasn't as overwhelmed as I was in the beginning because I had already made all of the measurements once and pretty much knew what I needed and where to go to get them.

When starting from scratch, I was pretty frustrated fighting around the tires trying to get the first couple of sets of measurements. Over time I developed ways to get around things that made it easier to get around obstacles.

[diesel25lrs]

Thanks Lance,
I'm thinking that without lift access it will probably be worth it to just fab up some hub mounted stands of some sort...up and down adjustability will be key though.

[SSLance]

Yeah, you need the car 10" off of the ground at least as you have to be all over the underside of the car.

I'm going to build some crib stands to use with my 2 post lift at home to do this in the future.

[Ron Sutton]

Hey Guys,

I'm going riding quads with my girls now ... so I'll catch up with everyone when I get back Monday.

Take care all !!! :cheers:

[Rod]

Hey Guys,

I'm going riding quads with my girls now ... so I'll catch up with everyone when I get back Monday.

Take care all !!! :cheers:




Have fun Ron!!!

[rustomatic]

As math goes, I've always labeled geometry as my favorite, but this thread is making me like statistics a bit more (while slightly hating geometry). At least I've now found what is perhaps the greatest benefit of my relatively new screw-in lower ball joints: I can (somewhat easily) take them out and buy new ones that give me more geometrical quandaries to ponder.

Thanks Ron, Lance, ancient Greeks. I'll now happily return to planning the angle grinder destruction of the rear end of my transmission tunnel, which was necessitated by geometrical changes in my driveshaft/rear axle...

[SSLance]

Little progress this weekend... I got the rear springs in the car and drove it around a bit to feel it out. Then things went a bit wonky. Pressing the stock ball joints out of the new A-Arms went pretty well, but pressing the new Howe Ball Joints back in them gave me a few fits. Seems the housing kept wanting to go in the arm a bit crooked. Finally just sent them with my friend John to his machine shop to use the good press to get them to go in straight. This delay kept me from getting to anything else on the front this weekend though.

We've got an autocross this coming Sunday so I'll run it with the new rear springs, new front 36 mm sway bar and street tires...and run the camera on the sides pointed at all 4 wheels to do a direct comparison to the first video in this thread. Then after that I'll have a month off to complete the front end changes and really make a difference.

[Ron Sutton]

Little progress this weekend... I got the rear springs in the car and drove it around a bit to feel it out. Then things went a bit wonky. Pressing the stock ball joints out of the new A-Arms went pretty well, but pressing the new Howe Ball Joints back in them gave me a few fits. Seems the housing kept wanting to go in the arm a bit crooked. Finally just sent them with my friend John to his machine shop to use the good press to get them to go in straight. This delay kept me from getting to anything else on the front this weekend though.

We've got an autocross this coming Sunday so I'll run it with the new rear springs, new front 36 mm sway bar and street tires...and run the camera on the sides pointed at all 4 wheels to do a direct comparison to the first video in this thread. Then after that I'll have a month off to complete the front end changes and really make a difference.



Sound good Lance.

Obviously we still have the front geometry problems & roll center too low & off to one side. The front tires will still want to push, just maybe not as bad with the stiffer rear springs. Once you have time to correct the front end geometry, move the roll center & add caster ... the front end will have more grip, and that is when we'll see a noticeable lap time improvement.

I'm back from my quad trip, so I can answer questions if you have any.

We went on an epic 7-1/2 hour quad ride up several mountains in the Sierra Mountains in Nevada & California. From 7000' to 11,700' through a wide variety of rough terrain, rocks, creeks, broken shale. My wife flipped over once, but was OK. She's a sweet, but tough gal. We saw breath taking scenery on several mountaintops looking out over the range, went partway into old gold mines that were caved in, rock & wood cabins where miners lived. We were all worn out from the ride.

[SSLance]

Sound good Lance.

Obviously we still have the front geometry problems & roll center too low & off to one side. The front tires will still want to push, just maybe not as bad with the stiffer rear springs. Once you have time to correct the front end geometry, move the roll center & add caster ... the front end will have more grip, and that is when we'll see a noticeable lap time improvement.

I'm back from my quad trip, so I can answer questions if you have any.

We went on an epic 7-1/2 hour quad ride up several mountains in the Sierra Mountains in Nevada & California. From 7000' to 11,700' through a wide variety of rough terrain, rocks, creeks, broken shale. My wife flipped over once, but was OK. She's a sweet, but tough gal. We saw breath taking scenery on several mountaintops looking out over the range, went partway into old gold mines that were caved in, rock & wood cabins where miners lived. We were all worn out from the ride.




Yeah I know, I thought about just putting the LCAs (with stock ball joints) and the spring adjusters in by themselves, then going back after next weekend to finish everything else up but I really dislike doing things twice, especially when coil springs under pressure is involved. If everything would have went perfectly smooth, I might have got it all in last weekend, but that wasn't meant to be.

Besides, the weather was perfect here for a boat ride and just like yourself on the ATVs, sometimes you just have to get away and play for a while instead.

We can always work on the car when it's raining...right?

[Ron Sutton]

Yeah I know, I thought about just putting the LCAs (with stock ball joints) and the spring adjusters in by themselves, then going back after next weekend to finish everything else up but I really dislike doing things twice, especially when coil springs under pressure is involved. If everything would have went perfectly smooth, I might have got it all in last weekend, but that wasn't meant to be.

Besides, the weather was perfect here for a boat ride and just like yourself on the ATVs, sometimes you just have to get away and play for a while instead.

We can always work on the car when it's raining...right?

We can't use that reasoning out here ... because it doesn't rain from May to November. :)

.

[rod cole]

Ron from what I understand from what you stated. Could a person put the vehicle on turn plates and add caster until the spindle/wheel stayed level to the max available turn radius. Thus achieving what you are doing with math? And does the correct amount of caster for a given spindle give the same camber whether turned in or out? Thanks Rod

[Ron Sutton]

Hi Rod,


Ron from what I understand from what you stated. Could a person put the vehicle on turn plates and add caster until the spindle/wheel stayed level to the max available turn radius.
I'm not 100% certain of your question, but If I understand it right, the answer is ...

If you place the wheel at zero camber ... and set the degree of caster to exactly match the degree of KPI in the spindle ... then as you rotate the wheel & spindle forward ... it will remain straight up & down ... plumb ... 0.0° ... meaning the caster counteracted the KPI. But when you rotate the wheel & spindle backwards ... the degree of caster & the degree of KPI in the spindle COMBINE to lean the tire towards the inside of the corner.

Did that make sense?

Thus achieving what you are doing with math?
Correct.


And does the correct amount of caster for a given spindle give the same camber whether turned in or out?
That's a tricky question. What is the correct amount of caster? That will vary somewhat with track, driver & philosophies of the set-up person.

For tight tracks, I like to run 1.0° to 1.75° more caster than spindle KPI. On bigger, faster tracks, with high speed sweeping corners, that may make it too free on entry or middle ... frankly anytime the driver uses excessive steering input.

But at no time does caster keep the dynamic camber the same if you turn the wheel forward versus backwards. As stated above ... If you place the wheel at zero camber ... and set the degree of caster to exactly match the degree of KPI in the spindle ... then as you rotate the wheel & spindle forward ... it will remain straight up & down ... plumb ... 0.0° ... meaning the caster counteracted the KPI. But when you rotate the wheel & spindle backwards ... the degree of caster & the degree of KPI in the spindle COMBINE to lean the tire towards the inside of the corner.

If that didn't make sense, just bring up the parts that don't & I'll be happy to explain it.

Bets wishes.




Thanks Rod

[rod cole]

So what I am shooting for is when the left wheel is turned into a right corner. I want the wheel to stay 0 or negative camber by adding caster to offset KPI yes? Thanks Rod

[Ron Sutton]

So what I am shooting for is when the left wheel is turned into a right corner. I want the wheel to stay 0 or negative camber by adding caster to offset KPI yes? Thanks Rod

There is more to it than that. You don't want to rely solely on caster. You want to build your steering geometry with a "happy combination" of KPI, caster, caster gain, camber, camber gain ... while taking into account the body/chassis roll angle.

I'll repost the info on the concept ... then the process I use to build a "happy combination" ... and after you read it, if anything isn't clear, post your questions & we'll discuss it deeper. Here goes ...

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Front End Geometry

Most everyone knows camber, caster & KPI/SAI work together, but most don’t really understand HOW they work together & how they affect each other. I’ll do my best to explain it, but we’ll need to peel the onion one layer at a time, so bear with me.

For those that don’t know what this is, KPI stands for King Pin Inclination & SAI stands for Steering Angle Inclination. They mean the same thing.

KPI was a term coined back in the day of solid front axles when spindles actually used king pins. Steering Angle Inclination is a more correct modern term & is calculated simply by running a theoretical line through the upper & lower ball joints & comparing that angle to the actual spindle pin the hub spins on (rolling axis in the photo). (I use both terms because many race car guys are used to the older term of KPI.) .

Think of caster as “dynamic camber” … since caster has no affect on angle of the tires & wheels … until you turn the steering. Then caster is tipping the top of BOTH tires towards the inside of the corner you’re turning into (Good).

KPI angle is important to keep the scrub radius lower. You can look at the illustration above & imagine how big the scrub radius would be if the KPI was straight up & down. If the front tire stays in the same location more KPI makes the scrub radius smaller. Less KPI reduces the KPI.

A bigger scrub radius means the tire is farther from the steering pivot … making the arc bigger that tire has to make in order to pivot. Not a big deal at low speeds, but in track conditions, at higher speeds, with the tire at its limit of grip … when you turn the wheel more, you are “torquing” the tire tread around a big axis to turn. This “rips” the tread across the pavement, causing the tire to lose a degree of grip. The bigger the scrub radius ... the higher degree of grip is being lost when you turn the steering. A zero scrub radius means the center of the steering pivot & the center of the tire tread are the same. This pivots the tire right in the center of the tread reducing lost traction to the minumum. KPI has pros & cons.

Think of KPI as a different kind of “dynamic camber” … since it also has no affect on the angle of the tires & wheels … until you turn the steering. But unlike caster, it is not tipping both tires towards the inside of the corner you’re turning into. KPI is tipping the top of the outside tire out towards the outside of the corner you’re turning into (BAD) and tipping the top of the inside tire in towards the inside of the corner (Good).

When the KPI/Caster Split favors the KPI … the tire & wheel, on the outside of corners, goes into a state of positive camber (BAD) … rolling over on the outside part of the tread and sidewall of the tire … with the inside part of the tread becoming unloaded. Basically, at this point, the actual tread making contact with the pavement (contact patch) gets narrower, making it incapable of maintaining the speed it was capable of an instant earlier, when it had a full contact patch.

Now let’s talk about the tire on the inside of the corner. Some cars roll so much the inside suspension goes into a “droop” or state of extension … and if that car has negative camber gain built in … the droop actually helps the inside tire stand straighter. For cars don’t roll as much … and that compress the suspension on the inside tire & wheel when cornering, the negative camber gain on the tire on the inside of the corner is tilting that inside tire the wrong way. It is rolling over on the inside part of the tread and sidewall of the tire … with the outside part of the tread becoming unloaded. Also making the contact patch narrower, making it incapable of maintaining the speed it was capable of an instant earlier, when it had more contact patch.

So your front tires that were already at their limit of grip … just lost a significant amount of contact patch & essentially got narrower … and lost even more front traction … creating a push or understeer condition.

The amount of dynamic camber loss is minimal with slight amounts of steering input on large sweeping corners, but grows exponentially worse with higher rates of steering input (front wheel steering angle) on tighter corners. More caster would help both situations … creating more dynamic camber the correct way for both tires … keeping the tire contact patches flatter on the track surface. But how much is enough? Read on.

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Now let’s discuss how Caster & KPI can work together for an optimum combination …

Racing spindles run the gamut of KPI angles. In oval track stock cars where the control arms are pretty average in length & the wheels are out wide … making the scrub radius bigger … racers typically run spindles with 8-12 degrees of KPI. In Trans Am & other road race cars where the control arms are longer & the wheels have a lot of back spacing … making the scrub radius smaller if not zero … racers typically run spindles with 3-5 degrees of KPI.

For the street & Pro Touring market, there are a lot of spindle options … usually with KPI somewhat in the middle of the extremes outlined in the racing paragraph above. Many Ford, Mustang II, Wilwood Pro Spindle & the ATS spindle from Speedtech all have 8.0 degrees of KPI. A lot of GM spindles have 8.75. I believe the C6 is 9.15. For our conversation … and math purposes … let’s use a spindle with 8.0 degrees of KPI/SAI as our sample.

If you were to set both the caster & camber at zero … and rotated the spindle 90 degrees each direction … the difference would be 2x the KPI/SAI angle of 8.0 degrees … so in this case 16.0 degrees.

We know the wheels don’t turn anywhere near 90 degrees, but this example makes everything more clear. Please humor me & follow along closely, because I’m about to share something that is one of the most overlooked keys to proper cornering set-up. We will account for the ACTUAL steering turning radius later.

If you rotate the spindle 90 degrees toward the front (like the wheel is turning on an outside corner) the tire & wheel experience 8.0 degrees of camber loss (goes into positive camber). Bad … very bad for the outside tire of a corner. :(

If you rotate the spindle 90 degrees toward the rear (like the wheel is turning on an inside corner) the tire & wheel also experience 8.0 degrees of camber loss (goes into positive camber). But this good for the inside tire of a corner. :)

Reminder, obviously we are not turning the wheel 90 degrees in the real world, so don’t lock in on the numbers “too much” … just the concept.

Caster is different. If we set caster at 8.0 degrees positive (top to the rear) & leave KPI/SAI out of the equation, as if we had a spindle with zero KPI/SAI … and you rotate the spindle 90 degrees toward the front (like the wheel is turning on an outside corner) the tire & wheel experience 8.0 degrees of camber gain (goes into negative camber). The right direction for the outside tire in a corner.

If you rotate the spindle 90 degrees toward the rear (like the wheel is turning on an inside corner) the tire & wheel experience 8.0 degrees of camber loss (goes into positive camber). And this is the right direction for the inside tire of a corner.

So … caster helps both the inside & outside wheel & tire. :)

Here’s the most important piece of info to know at this point. It is the first & most important key to getting the front tires to use their full contract patch when cornering … increasing front end grip & turning speed. Drum roll please …

Caster offsets KPI/SAI on the wheel & tire on the outside corner … and compounds (adds to) KPI/SAI on the wheel & tire on the inside corner. :)
Read that again. It’s very important.


This is called KPI/Caster Split. When the Caster & KPI are equal … the caster offsets the negative effects of the spindle KPI on the outside wheel ... and compound the advantages of the KPI on the inside wheel. When the KPI is greater than the caster (unless the car has a TON of Camber) the outside wheel is going to lose camber as the steering is turned & roll over on the outside front tire. Ugly.

The greater the split is favoring the KPI, the worse the problem. On the other hand if the KPI/Caster split favors the caster … meaning the caster is slightly greater than the KPI, the outside wheel is going to gain camber as the steering is turned, creating a flatter, better tire contact patch. The inside wheel also gets cambered the correct direction (for the inside wheel) and both front tires stay flatter to the road, have more grip, better turning & higher corner speeds.

Sooo … if we set the car up using spindles with 8.0 degrees of KPI/SAI and 8.0 degrees of caster … and you rotate the spindle 90 degrees toward the front (like the wheel is turning on an outside corner) the tire & wheel experience 0 degrees of camber gain or loss. Frankly it is zero, no matter what degree you rotate it to the front, because 8.0 degrees of caster counteracts … or neutralizes … the 8.0 degrees of KPI/SAI.

If you rotate the spindle 90 degrees toward the rear (like the wheel is turning on an inside corner) the tire & wheel experiences 16.0 degrees of camber loss (goes into positive camber). This is the right direction for the inside tire of a corner … way too much ... but we’re not turning 90 degrees. We’re turning somewhere from 0 to 25 degrees. What if the wheels were turning 15 degrees? … that’s 1/6 of 90 degrees … times 16.0 … equals 2.67 degrees … the right direction.

At this early point in peeling the layers of the onion ... we have:
Outside Front Tire at 0.0 degrees (OK)
Inside Front Tire +2.67 degrees (Good)

You’re probably going “Hmmmm” … but we don’t have the whole picture yet.
We have a lot of other geometry to factor in. Remember, we’re peeling this onion a layer at a time, so we’ll get to camber gain, chassis/body roll angle & static camber in steps.

Camber gain & chassis roll angle are next. Chassis roll angle hurts the contact patch of both tires. Camber gain (towards negative) helps the contact patch for your outside tire & hurts the contact patch for the inside tire.

Chassis/Body Roll Angle
Stock production cars have a HIGH roll angle when pushed to their limits. Pro level race cars running high travel/low roll angle suspensions … obviously have pretty low roll angle. But’re we’re talking modified PT cars for track purposes. Way better than stock production cars, but not quite race cars.

Because higher roll angles are an enemy of proper geometry & optimum contact patch … for this conversation let’s say we’re running a milder version of the high travel/low roll suspension … and have 1.5 degrees chassis/body roll in the corners. Obviously any chassis/body roll is ot the outside of the corner … and therefore hurtful to the contact patch angle of both tires.

If we add chassis/body roll angle into our numbers above, now we have
Outside Front Tire +1.50 degrees (Bad)
Inside Front Tire +1.17 degrees (Good)

Camber Gain
On the outside tire, if you worked out your camber gain to be 1.5 degrees negative “in dive” … and assuming we have a modern low roll angle suspension with chassis/body roll angle of 1.5 degrees … those two just neutralized each other. The inside tire, of this car in the same corner, is compressed, but not as far, so it doesn’t have as much camber gain towards negative (reminder: camber gain towards negative is bad on the inside tire).

Let’s say we end up with 2/3 the compression travel on the inside tire & end up with 1.0 degrees negative camber gain (the bad direction for the inside tire) … so what does that do for us at this level of “onion peeling”?

Dynamically we have:
Outside Front Tire 0.0 degrees (OK)
Inside Front Tire +0.17 degrees (OK)
Not optimum yet, but we’re going the right direction & we’re not done yet. :)

The next layer of the onion is static camber.
You need SOME static camber … to help with initial steering turn-in responsiveness. Just don’t get greedy. In road racing or AutoX where you’re turning left & right, static camber is like camber gain. It helps the contact patch on the outside tire & hurts on the inside tire. For this example, let’s add 1.0 degrees of static camber.

Now with static camber added … with your car hard in the corner … suspension in dive, wheel turned 15 degrees for a tight corner …

Dynamically we have:
Outside Front Tire -1.0 degrees (Good)
Inside Front Tire -0.83 degrees (Bad)
Not optimum yet, but we’re we’re not done yet. :)

Now, here is another part I love. You simply add caster until the contact patches of both tires are flat & happy. And from this point the math is easy.

Add 1.0 degree of caster and …
Outside Front Tire -2.0 degrees (Good)
Inside Front Tire +0.17 degrees (Good)

Add 1.25 degree of caster and …
Outside Front Tire -2.25 degrees (Very Good)
Inside Front Tire -0.42 degrees (Very Good)

Add 1.5 degree of caster and …
Outside Front Tire -2.5 degrees (Very Good)
Inside Front Tire -0.67 degrees (Very Good)

There are many factors that will define your optimum set-up, but this creates a baseline that is darn close.

**P.S. I like to end up “around” 1.5-2 degrees more dynamic camber on the outside tire, since the outside tire is loaded so much more.

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There is a little more involved in this, when you involve exact steering angles for specific corners. The good news is … when you run tighter corners requiring more steering angle than 15 degrees … the caster increases the dynamic camber to help the tires maintain flat contact patches. I use a spread sheet I developed to plug in all the info & know exactly what dynamic camber I have at different steering angles & different camber gain & different suspension travels.

The best way I have found to work out a front end setting is to start with KPI/SAI & caster … then bring in camber gain … and finally static camber … to achieve the optimum dynamic camber for BOTH tires. Regardless of how you get there ... all of these geometry pieces need to work together in harmony to achieve full, optimum contact patches for both front tires in hard cornering situations … for optimum cornering grip & speed.

It probably is clearer now why getting advice on one setting that worked for a buddy’s car … without knowing the whole picture … can be misleading. As a tuner, I couldn’t imagine setting the caster without knowing the spindle KPI & the car’s camber gain … and then of course testing on track with tire crayon on the edges every run (plus taking tire temps).

It’s been said a zillion times. It’s the whole package, not one part or one setting.

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Remember the KPI/Caster Split concept ... if the caster is slightly greater than the KPI, the outside wheel is going to gain camber as the steering is turned, creating a flatter, better tire contact patch. The inside wheel also gets cambered the correct direction (for the inside wheel) and both front tires have more grip, better turning & higher corner speeds.

When I'm designing a front suspension for a specific class with rules on what spindle we can run, I pick the best spindle available under the rules and design everything else to either fix or compliment that spindle. Factory spindles usually have KPI/SAI ranging from 7-10 degrees. When I have to run a factory spindle ... I know I'm going to end up with 1-2 degrees of caster more than the KPI.

I designed & raced NASCAR Modifieds with Factory GM #2 spindles with 8.75 KPI. 10-10.25 degrees of caster produced awesome results. We had a crew chief go off the range with set-ups & try 6-7 degrees of caster, but the cars always pushed in mid corner ... and snapped loose on exit. He was used to running less caster, but didn't take into account the KPI of the spindles we had to run.

The whole combination of KPI/SAI, caster, caster gain, camber, camber gain, Ackerman, toe, steering ratio, etc. ... ALL have to be designed together for optimum cornering performance. All of them are important, but the KPI/Caster Split is critical & often not fully understood.

When I'm designing a front suspension with no rules on what spindle we can run, I design the spindles & have them built. Then I'm not trying to fix anything ... and everything else in the front suspension can be designed to compliment that spindle. For a road racing car, I designed the spindle with 3 degrees of KPI/SAI ... and designed the rest of the the front suspension around what is called a "zero scrub" set-up ... & we ended up with 4.0 degrees of caster for optimum handling. This car did NOT require a high caster number, because the spindle KPI was lower. What is optimum for tight cornering is having the KPI/Caster Split slightly favoring the Caster.

Another successful car I designed with 5 degrees of KPI/SAI ... ended up with optimum handling with 6.5-7.0 degrees of caster ... depending on the track. Again, the key was the KPI/Caster Split slightly favoring the Caster.

This higher amount of caster seems odd to most veteran mechanics & street car guys used to running 1-3 degrees of caster. But when you look at the newer Corvettes, Vipers, BMW’s, Mercedes, Etc. … you'll see they run a lot more caster than what most think of as "typical”. The Factory GM specs for the C6 ZR1 is 7.7-8.3 degrees of caster. But owners that compete & win in the C6's increase the caster to 9.5-10.5 degrees of caster ... with the KPI/Caster Split favoring the Caster.

The common denominator is we are almost always running more caster than KPI/SAI ... if we can. . We run spindles with lower KPI where we can too ... but it requires running wheels with DEEP back spacing to get the scrub radius low (or sometimes zero). So simply ordering a spindle with smaller KPI is NOT a bolt-on solution.

There are a lot of spindle options, including custom spindles, which cost less than most folks think. One BIG question in this equation though is Scrub Radius. For optimum AutoX performance. Scrub Radius is important. The smaller the better … down to zero … and KPI/SAI plays a big role in this.

The first goal with Scrub Radius … if possible … is reducing it, so the tire is not having to torque itself around a big radius when you turn the wheel. If that is not possible … the 2nd goal would be … at least not making it bigger. Caster, KPI/SAI, wheel back spacing & Scrub Radius … all need to be worked out together. You should not arbitrarily pick a spec for any one of these things without considering how they affect each other.

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How do you work out a front end geometry combination?

All of us know that each front suspension geometry setting affects the overall picture ... and to a degree ... each other. As a race car Designer & Crew Chief, I can't look at just one individual setting. I have to look at the spindle KPI/SAI, Caster, Caster Gain/Loss, Camber, Camber Gain/Loss as a team ... a team of geometry devices that I need to work together in harmony to improve how the tires contact the road dynamically.

Having done this for years, designing, building, tuning & racing a lot of cars, in just about every type of racing, has given me some firsthand insight into how all these things work. So now it's a little easier & quicker for me to "get a set-up there" to the sweet spot. I have a process that gets me there quickest ... with the least back-n-forth.

First … some guidelines:
Zero scrub radius with long control arms & deep backspaced wheels is optimum, but many race series rules prevent us from achieving this, with rules on the LCA. If the rules allow, we're running long control arms & a low KPI spindle on deep backspaced wheels & achieving low to zero scrub radius.

But when the rules restricting our LCA choices prevent us getting the ball joints "out there" … making us choose between track width & scrub radius … we are “usually” going with wheels with less backspacing to achieve the maximum track width allowed by rules … then running higher KPI spindles to reduce the scrub radius as much as we can.

I've had people ask me why don't we give up track width to achieve a lower or zero scrub radius ... but in the big picture ... track width trumps scrub radius, up to a point. Everything has its limits & there are exceptions for everything. Tight AutoX courses sometimes favor narrower cars with narrower track widths. But most anything faster than that … like road course … favors a wider track width. When you have no rules or limitations, you making everything optimum. When rules prevent that, you’re shooting for the best overall compromise.

I have a step-by-step process I follow ...
with the goal being optimizing the contact patch of both tires, while turning hard on tight corners of AutoX tracks or Road Courses .

A. I have to work out the Spindle KPI/SAI with the length of the A-arms, tire width & wheel backspacing ... to end up with a desirable scrub radius.

When I’m working out a car for class rules, those rules often limit what you can do for spindles & wheels. In more unlimited series there are less rules. On the street, there are no rules, except the ones you impose based on your desires, budget & priorities.

If I have a scenario where we are running front wheels with a lot of backspacing … that gets the KPI/SAI closer to the center of the tire … reducing Scrub Radius. “Zero Scrub” is optimum, but challenging to achieve for packaging reasons. It requires very wide wheels & deep backspacing. You can go too far ... with REALLY DEEP back spaced wheels & HIGH KPI/SAI spindles … you can get into a situation of negative Scrub Radius, which isn’t desired.

I recently designed a front end with 12” wide wheels & 10” of backspacing. A 8-10 degree KPI/SAI spindle would have put it into negative Scrub Radius. The spindle design & hub design also play a part on the packaging with the distance from the steering axis to the wheel hub face. With the hub we used & a 5 degree spindle, it created a zero scrub radius package.

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B. Once I know the spindle KPI/SAI, that guides me on how much “static” caster I need to build in to achieve a KPI/Caster Split favoring the caster.

Optimally, we need the 1.0-2.0 degrees more caster than KPI/SAI angle. A lot of Ford passenger cars run 8.0 KPI, so we’re shooting for 9.0+. A lot of GM spindles are 8.75 KPI, so we’re shooting for 10.0 +/-. If we can run a lower KPI/SAI spindle … like in the example above using a 5 degree KPI spindle … we’ll need 6.0+ degrees of caster.

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C. I need to work out if we want caster gain, or for the caster to stay the same, as the front suspension compresses fully under braking & turning (Term = "Dive") Think of this as “dynamic” caster, because it only happens when the suspension is compressed.

Quick Primer: When the front suspension compresses, if the angles of the lower control arm cause the lower Ball Joint to move forward and/or the angles of the upper control arm cause the upper Ball Joint to move back … that creates camber GAIN … in dive (compression). When the front suspension compresses, if the angles of the lower control arm cause the lower Ball Joint to move back and/or the angles of the upper control arm cause the upper Ball Joint to move forward … that creates camber LOSS … in dive (compression). We never want loss. When the front suspension compresses, if the angles of the lower control arm and/or upper control arm combine for no change in the ball joint locations … that is considered Caster Neutral. *Ask if you want the “how” explained more in-depth.

If we can get all the “static” caster we need, we will typically run only a small amount of caster gain. If we can’t get enough static caster, we need to build in more of caster gain to help us get to the desired total number.

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D. If I can get the caster I want ... statically and/or with gain ... so the KPI/Caster Split favors the caster 1.0+ ... I can run less Camber, which is the goal. We're always going to run SOME static camber (negative) … say –0.5 at a MINIMUM … and we always want SOME Camber gain … but if we don’t end up with a KPI/Caster Split favoring the Caster by 1.0+ degrees … then we need to make the difference with Static Camber & Camber Gain.

This is NOT ideal, because Camber by itself helps the angle of the outer tire achieve optimum contact patch … and hurts the angle of the inner tire, preventing optimum contact patch. The more static camber & dynamic camber we have to run … to make the outer tire work best … the more it hurts the contact patch of the inner tire.

If we can get to the optimum angle with a KPI/Caster split favoring the caster by 1.0+ degrees … either statically or in dive … we will run smaller amounts of static camber & camber gain. This is optimum. But if we don’t … we’ll run all the camber we need to … to make that outer tire WORK.

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E. Once I know how much camber I need for that combo, I work out how much of it is going to be static camber & how much is going to be camber gain.

We always want some static camber. -0.5 is like the minimum. I like -1.0 to -2.0 … IF everything above falls into place.

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F. How we get the camber gain, & how much, affects the car's static & dynamic roll center ... so they have to work as a team too.

Our desired roll center plays a role in this decision, because all the A-Arm angles creating Instant Centers determines where the static Roll Center is ... and where it goes dynamically in dive.

It should be clear now why I don't start with Camber.

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All of this ... is to optimize both front tire's contact patch with the asphalt ... In the car's dynamic states when it's driven HARD ... meaning turning, braking, rolling, unwinding & accelerating to the limits of the car, tires & driver ... sometimes beyond.

I realize this is a lot to digest. Don’t be afraid to ask questions where ever I wasn’t clear.

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*Caster gain is achieved when the front A-arm geometry is set for anti-dive. Zero caster loss or gain is achieved with zero anti-dive. Caster loss is achieved when the front A-arm geometry is set for the opposite of anti-dive … called “pro-dive.”

** The more static camber you have to run to optimize the outside tire, the more you’re hurting the inside tire. I like to get 50%-60% of the total camber desired … through camber gain. Here is why: The suspension on the inside of the corner is not compressed as far as the suspension on the outside corner. So effectively … the inside tire is not getting as much negative camber gain to fight & overcome.

*** Don’t get greedy with static camber. Yes it improves initial turn-in steering response, which is good. But two things:
1. Camber helps the outside tire & hurts the inside tire. If you run too much static camber, you can’t get the inside tire to work optimum.
2. There are a LOT of other things that help turn-in response … so use some of those … & don’t get greedy with static camber.

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You know how people say a little information can be dangerous? This is one of those times.

If your PT car has a Moderate to High scrub radius … you have to be careful with how much caster you can put in the car … because caster combined with a moderate to high scrub radius creates a “jacking effect” when you turn the wheels. Dynamically, this jacking effect “de-wedges” the car … loading the inside front & outside rear tires more … while also unloading the inside rear tire & increasing the degree the car diagonally rocks & loads the outside front tire.

All of this helps the car to turn better. But go too far … and the car will get loose on entry. This is where track tuning comes into play. If you have a moderate to high scrub radius … sneek up on the caster you put in the car … until you get the car “free” on entry … then reduce the caster a tick … or tune something else to allow you to keep that amount of caster, so the car turns well in the middle. But do NOT keep a set-up that makes the rear loose & stepping out on corner entry.

Make sense?


In my experience & by my personal scale ...
0-1/4" = Zero
1/4"-1" = Very Low
1-2" = Low
2-3" = Moderate
3-5" = High
5-7" = Very High
7" + = Extreme

* But this relative to the situation. When we designed a new Modified chassis that dropped the Scrub Radius from over 7" to under 5" ... we thought of that as "low scrub radius” ... for the NASCAR Modified class we raced in.

[rod cole]

Got it. Currently have stock G-body spindles 3/4 taller lower ball joint and 1/2 taller upper with 1/2 shorter upper arms. Looks like in youre example I am going to need 9 plus degrees of caster to offset the spindles most likely requiring moving the lower ball joint forward to reach these numbers. Thanks for you,re expertize. Rod

[Ron Sutton]

Got it. Currently have stock G-body spindles 3/4 taller lower ball joint and 1/2 taller upper with 1/2 shorter upper arms. Looks like in youre example I am going to need 9 plus degrees of caster to offset the spindles most likely requiring moving the lower ball joint forward to reach these numbers. Thanks for you,re expertize. Rod


You are on track with the amount & method for tight cornering.

[SSLance]

So just to update where I'm at with the car now... I've made a couple of the changes Ron suggested already as I had the parts on hand and available time to make them. I put the 36 mm sway bar up front before the last autocross 2 weeks ago and I put the new rear springs in before this week's autocross. Now that I've got a month off before the next event, I'm ready to tackle the major pieces of the recommended changes, new LCAs, taller lower ball joints, repositioned LCA mounting holes, coil spring adjusters to raise ride height and adjust weight, the bump steer kit and the associated alignment settings once the parts are in place.

I ran the bigger front bar last event with the R-comp tires I'd been running most of the season. I could tell the car was staying flatter, not rolling over near as much and this seemed to help keep the front planted better. I ran a camera pointed at the front suspension that event and discovered that not only is my frame flexing around quite a bit, but also I was running way too low of a tire pressure in the R-comps and was really rolling over the sidewalls and the tire slip angle was huge. Data collection is huge and the GoPro helps tremendously with this.

I then put the stiffer springs in the rear along with the adjusters. An unexpected consequence of this addition to me was about an inch of ride height increase in the back, even with the adjuster flange back out and the springs just set on the base of the adjuster. I wanted to drive it with the stiffer springs in anyway to see how it drove, knowing the increase in ride height would upset other parts of the car and that this would be temporary until I finished up the front end changes. Here is how it sat before yesterday's event.

https://static1.pt-content.com/images/pt/2013/08/IMG_20130811_100544_840-1.jpg

Little too much rake which I'm certain had a negative effect on the roll center. I don't want to spend too much time on what it screwed up as it's all going to change again very soon. I also ran my street tires yesterday for the first time since April, brand new sticky Rivals up front and wore out Nitto 555s out back.

I kind of figured the mis-mash of changes would be entertaining, add in a Gymkhana style course setup for this event...and well...it was.

I was WAY loose entering into corners. The front was stuck pretty well, I can't remember ever losing or pushing the front tires more than just a little bit of squealing but I was struggling getting into corners which was messing me up pretty good. It seemed like the car wasn't rolling over near as much though, with the big bar up front and stiffer springs out back, it seemed to run more flat. And traction off of the corners was much better as well, it didn't want to seem to try to spin the tires off of a corner as long as I wasn't already sliding the rears because of loose in.

After my second run (with some road rage mixed in from a missed cone\DNF) we had an oil down from a blown power steering line and about a 45 minute delay. With nothing to do and still a bit fuming over my last run, I texted Ron with an update on my progress. He was by his phone and texted me right back. I explained how it was going, about being loose in...and he helped me with a few driving tips to help counteract the condition for the last two runs.

I can't tell everyone here how much I appreciated his help at that time. What an unbelievable resource, and the fact that he is texting me, on a Sunday afternoon, from halfway across the Country...blew my mind. Thanks Ron!

Ron told me to brake a bit earlier and a bit softer and to work on picking the throttle up sooner on exit. In my mind...that meant, slow down...to go faster....and it worked. I picked up almost 2 seconds on my 3rd run and it just felt better overall. Picked up another 2\10s on my 4th run but also a cone.

Here are my runs from the weekend http://youtu.be/xRvExmeX82U

And here are the final best raw times in order

http://www.kcrscca.org/results/solo/2013/2013_event9_raw.htm

1985 Chevrolet Monte Carlo SS Maroon (1) 71.176 (2) 70.841+dnf (3) 69.134 (4) 68.929+1

So anyway, now the real fun can begin. I'll start disassembly of the front end this week and will document here the making of the major changes Ron prescribed and then if all goes well, get some testing video and then event video from our next autocross on Sept 15th.

My personal goal is to get this car to run as fast on street tires as similar cars I race against run on R-Comps and I think it can be done. Especially if the driver keeps his head in the game.

[Ron Sutton]

Great update Lance.

I was a little leery of you running just 2 of the 9 changes we planned. Sometimes that gets real ugly. :lol:

Here, the result was actually pretty good.

------------------------------------------------------------------------------------------------------------------

On a somewhat different note, as you move to a "Tweener High Travel/Lower Roll Set-up" ... you'll need to adapt your driving style as you did this last weekend. This type of set-up doesn't allow the driver to charge the corner as hard ... meaning it doesn't like late, hard braking. You'll need to brake a "little" sooner. How much sooner ... 5', 15' etc ... needs to be worked out in on-track testing.

And you need to brake a lot softer & a little longer. Again, how soft & how long will come to you from on-track test driving. You will want to slow the car "less" ... as you will be able to carry more corner speed with this set-up ... and that is where half of the lap time advantage comes from.

The other half of the lap time advantage comes on the corner exit. You will be able to get the car turned sooner & better. And you will be able to get on the throttle earlier & roll it to full throttle quicker. This is a big deal to the overall lap time. Bigger than most people think.

The simple summary of the this set-up will be:
a. Brake a little earlier, a lot softer & a little longer.
b. Slow the car less & carry more corner speed.
c. Get the car turned better & sooner.
d. Pick up the throttle earlier & roll it on quicker.

[SSLance]

Are you being easier on the brakes to keep the car from diving and unloading the rear tires on corner entry? Basically letting the car settle back to ride height before initial turn into the corner?

In other words, with this type of setup, where in the corner do you want the weight to transfer to the front, then the outside, then the rear on exit?

[Bryce]

What about on tighter and slower autocrosses?

Example: not alot of straight aways to accelerate therefore not a lot of braking to get the car to dive.

How does a low roll/ high travel setup work under those conditions?

[Ron Sutton]

Are you being easier on the brakes to keep the car from diving and unloading the rear tires on corner entry? Basically letting the car settle back to ride height before initial turn into the corner?
No. I'll outline below.

In other words, with this type of setup, where in the corner do you want the weight to transfer to the front, then the outside, then the rear on exit?

I'll outline the optimum driving style for both common suspension set-ups;

---------------------------------------------------------------------------------------------------------------------------------

For a Conventional Low Front Travel/High Roll Set-up:
You can drive this set up deeper on corner entry because the stiffer front springs will prevent the car from unloading the rear tires too much or too quick.

You need to drive this set-up deeper on corner entry ... and brake HARD ... to get the front end to compress as much as it can ... to get some loading on the front tires for cornering grip.

If you don't brake hard enough ... the front end won't travel enough to properly load & grip the front tires ... and the car will push once you really start to turn it.

If you brake too short ... or too soft ... you will have a mid-corner push.

If you brake hard too early ... and get off the brake too early ... the front springs will push the front end up too early & push bad in the middle of the corner.

If you brake hard too early ... and stay on the brakes long enough to prevent the front springs from pushing the front end up too early ... to avoid pushing bad in the middle of the corner ... you will have braked too long ... killing the corner speed.

Because this set-up is more prone to mid-corner tightness, push or understeer ... the car doesn't get turned or "rotated" soon enough ... and you have to wait on picking up the throttle.

If you pick up the throttle much before the car is turned or "rotated" ... it will push on exit ... until the front tires grip and snaps the rear of the car loose.

---------------------------------------------------------------------------------------------------------------------------------

For a Modern High Front Travel/Low Roll Set-up:
You can not drive this set up as deep & brake as hard on corner entry ... because the softer front springs will unload the rear tires too much, or too quick ... unloading & ungripping the rear tires ... and the car will be loose once you really start to turn it. This is easier to do because of the softer front springs and/or higher ride heights.

You need to brake a little earlier on corner entry with this set-up ... and brake substantially softer, but hard enough to get the front end to compress ... to load the front tires for cornering grip. This is easier to achieve with softer springs and/or higher ride heights.

If you brake too long ... you will kill the corner speed. Overall, you will need to brake less ... to keep the corner speed up ... to obtain the lap time advantage. This set-up will corner well at higher speeds. The same cornering speeds that would cause a push in a conventional set-up.

If you brake too soft or too short ... the front springs will still push the front end up too early & push in the middle of the corner ... just less than a conventional set-up.

Because this set-up is more likely to turn well in the middle of the corner ... you can pick the throttle up sooner ... and roll it on harder.

---------------------------------------------------------------------------------------------------------------------------------

Make sense?

[Ron Sutton]

What about on tighter and slower autocrosses?

Example: not alot of straight aways to accelerate therefore not a lot of braking to get the car to dive.

How does a low roll/ high travel setup work under those conditions?

Frankly, with how soft the front springs are ... it happens plenty quick. Also with the stiffness of the rebound valving ran in successful set-ups ... it is not coming all the way back up to ride height.

[SSLance]

Yeah, I gotcha...that makes sense. You need to time the braking to load the front tires at the optimum spot, but don't brake for too long or it'll scrub off too much speed.

This will be a big change for me at my next road course track day. I'm typically an easy braker on the road course, more coast into a corner then power out of it. My last instructor was trying to get me to charge the corner harder, brake more aggressively, then roll the corner faster.

[Ron Sutton]

Yeah, I gotcha...that makes sense. You need to time the braking to load the front tires at the optimum spot, but don't brake for too long or it'll scrub off too much speed.
Yup !

This will be a big change for me at my next road course track day. I'm typically an easy braker on the road course, more coast into a corner then power out of it. My last instructor was trying to get me to charge the corner harder, brake more aggressively, then roll the corner faster.

That didn't quite sound right. You will need to brake softer.

What your instructor was teaching back then ... is for a more conventional set-up.

[SSLance]

What I meant was, he was trying to teach me to charge the corners and brake harder...which I was working towards near the end of our session.

Now it sounds like with the high travel\low roll set up I'll have to back away from that a bit. And that's okay really as it might fit my more natural driving style better anyway.

[Ron Sutton]

What I meant was, he was trying to teach me to charge the corners and brake harder...which I was working towards near the end of our session.
You got it. I was just twisted up with the wording This is for conventional stiff front spring/low travel/high roll set-ups, :drive1:
where the goal is to charge the corner entry hard ... drive deep ... and brake hard.

Now it sounds like with the high travel\low roll set up I'll have to back away from that a bit. And that's okay really as it might fit my more natural driving style better anyway.

Yup. With modern, soft front spring/high travel/low roll set-ups, where the goal is to carry more corner speed, you brake a "bit" earlier, brake softer & a little longer ... but overall using less braking to keep corner speed up.
Then get'er turned & giddy up. :6gears: :1st: :)

[AJohn6]

So after reading this thread and being absolutely blown away by the amount of useful information on here I feel the need to thank Lance for having the courage and wherewithal to post his handling problems in a logical manner. Also I'd like to thank Mr. Sutton for answering the questions in such a way that even guys like me understand it and can hopefully start to apply it to my truck.

So...

Thank you guys for the support you have shown to the members of this forum.

-Adam

Also, I have some questions for you Mr. Sutton but I will PM you. I don't want to hijack the thread with my own questions.

[Ron Sutton]

So after reading this thread and being absolutely blown away by the amount of useful information on here I feel the need to thank Lance for having the courage and wherewithal to post his handling problems in a logical manner. Also I'd like to thank Mr. Sutton for answering the questions in such a way that even guys like me understand it and can hopefully start to apply it to my truck.

So...

Thank you guys for the support you have shown to the members of this forum.

-Adam

Also, I have some questions for you Mr. Sutton but I will PM you. I don't want to hijack the thread with my own questions.


Thanks for the kind words. PM your questions & we may start our own thread.

[SSLance]

Making a little bit of progress this week so far. Tuesday night I pulled the driver side LCA and coil spring out and put the DSE LCA with Howe tall ball joint in place with no coil spring. I then used the lift and some car ramps to cycle the suspension to the bump stop limits up and down while recording the shock length and fender height measurements every inch along the way. This will aid us when the time comes to set the adjuster height on the spring to dial in final ride height.

Here is the passenger side at current ride height and all of the old pieces still in place

https://static1.pt-content.com/images/pt/2013/08/DSC03193JPG-1.jpg

and here is the driver side at same height but with new LCA and BJ in place

https://static1.pt-content.com/images/pt/2013/08/DSC03191JPG-1.jpg

Notice the different tie rod end angles.

This picture shows the UCA bump stop on the passenger side

https://static1.pt-content.com/images/pt/2013/08/DSC03196JPG-1.jpg

And here is the driver side UCA bump stop with new parts in place

https://static1.pt-content.com/images/pt/2013/08/DSC03198JPG-1.jpg

Both pictures at current ride height as measured by the fender.

I then put a tape measure on the outside of the frame rail and measured to a tread block on the front of the tire (and also a second measurement to a framing square up against the outside of the tire) as I cycled the suspension from full compression to full extension to document how much bump steer is happening with the new LCA and the old tie rod end. That's where I stopped last night.

As it sits the tie rod adjuster contacts the frame just as the LCA bump stop hits the frame. Ron asked me to remove the bump stop and tie rod and cycle the suspension even further up, see what hits next and record shock and fender height measurements as I go...all to further document the new suspension travel points. Then I'll put the bump steer correction kit on the drivers side and measure the new bump steer travel at all points. Once armed with these measurements, Ron will direct me on how to set up the bump steer kit for optimum correction.

I've also been sourcing the needed parts and tools to correct and remount the LCA bushings in the cross member. Since this car is Metric, this was a bit of a difficult task. I ended up going to two local fastener stores and placed mail orders with 2 more stores to get everything I need. hopefully I'll have everything in hand by Friday and can make some serious progress this weekend.

Parts and tools purchased

M12-1.75x110 Socket Cap Screw 12.9 (2) (shoulder is 0.4685, ID of bushing is 0.4750)
M12-1.75x120 Socket Cap Screw 12.9 (2)
M12x24x3mm const. flat washer hard zinc plate (8)
M12-1.75 All Metal Top Lock ZP Nuts (4)
3' piece of 12mm drill rod
Flat Washer, Thick, Blk Oxide, Fits M12, Pk5 (2)

The last item being the hardest to find. Here is how they are described, Flat Washer, Extra Thick, Case Hardened Steel, Black Oxide, Fits Bolt Sizes M12, Inside Dia 13mm, Outside Dia 26mm, Thickness 5mm, Thickness Tolerance +0.4/-0.5mm, Rockwell Hardness C40, Load Distributing, For Use With Die And Jig Fixture Setup. Finding an extra thick, case hardened, M12 washer locally proved to be an impossible task.

I'll use the drill rod to put through the crossmember holes and LCA bushings and elongate the holes in the crossmember to place the control arms in the preferred position. The thick, case hardened washers will be what gets welded to the crossmember to hold the control arm bolts in place once the new positions have been set. Then the new longer bolts with tighter tolerances to the ID of the bushings will be used to hold the control arms in place while not restricting the movement of the control arms up and down.

That's where I'm at now, will update once again once more progress is made. Wish me luck on it all going smooth...

Lance

[Mizzouri]

Nice work Lance! I might have to step up to 315s when we race next season. :)

[SSLance]

This will be fun Patrick, the 2013 KC Region ESP and SM Champions going head to head in SMC in 2014!!

Are you going to be in a Camaro or a WS6 is the only question?

[rod cole]

On moving the lower control arm. I slotted mine a 1/8 to 3/16 and got about 9/16 at the ball joint. It stayed within the steel sleeves in my circle track solid bushings. I also put a come along and pulled the a frame forward while tightening the bolts to help in distorting the frame. Made my own .125 thick washers but not hardend. The stock bolts were long enough to fit everything. How far are you shooting for?
Slotted with die grinder and carbide bit

[SSLance]

It is amazing to me how much just a little of movement at the bolt translates to a large movement of the ball joint, still trying to wrap my head around that.

Ron will have to answer specifically how much we are looking to move the holes, but I think our first objective is to get the passenger side to match the driver side in lower ball joint placement and to get all 4 holes in the cross member on each side perfectly in line so there is no bind to restrict the up and down movement of the LCA, then go from there for more built in caster. I have room in the wheel well to move the tire forward as it sits back of center now. The further forward we go, the more adjustability we'll have with the upper control arm mounts. The downside of going further forward is greater bump steer movement and possibly clearance issues with the tie rods and sway bar.

We'll have to see how it all shakes out, but in the back of my mind, I'd love to see both sides exactly equal and 9+ degrees of positive caster with the inset slugs in my UCA cross bar offset back and be able to swap that slug to center or forward to have less positive caster (and bump steer) for daily driving. Easy changing from an optimum track setup to a street setup would be an ultimate goal for me, it remains to see if that goal can be reached though.

This exercise has been a great learning experience for me, I'm really starting to recognize how it isn't just a toe setting, or a camber setting, or even caster or KPI angle...it is how all of these settings work together as the suspension cycles up and down and the steering wheel is turned. We are trying to maximize all we can with all of these settings while working with the parts we have and the platform already in place. I can't wait to see how it all turns out.

[Ron Sutton]

Lance & I have discussed moving the lower BJ forward a total of .800" to gain 4° of caster "potential". The LCA from DSE moves the lower BJ .400" forward ... so we'll get the other .400"+ through LCA pivot modification.

In the end, you want the LBJ on both sides to be in identical in X & Y distances. And you want the pivot of the LCA to be 100% true, which most are not from the factory.

.

[SSLance]

28 year old rubber bushings...

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_112655_844-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_112721_181-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_112752_899-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_112806_174-1.jpg

New parts, full droop

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_111743_198-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_111751_913-1.jpg

Full stuff

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_111905_150-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130817_111924_097-1.jpg

Video of wheel travel with all new parts mocked in place.

New wheel travel - YouTube (http://youtu.be/3R3JEt0sn00)

Still don't have my drill rod or washers so no modification on control arm bolt holes done yet.

[diesel25lrs]

Awesome work Lance! Thanks for documenting everything so we can all learn! I hope to be there doing the same very soon.

[SSLance]

Since I was still waiting on my drill rod and right sized washers to get here, I didn't any parts to work with Sunday, I built some homemade alignment tools.

https://static1.pt-content.com/images/pt/2013/08/IMG_20130818_165252_046-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130818_174946_691-1.jpg

https://static1.pt-content.com/images/pt/2013/08/IMG_20130818_175003_960-1.jpg

Custom fender height measuring device...

https://static1.pt-content.com/images/pt/2013/08/IMG_20130818_174928_966-1.jpg

Slide plates...

https://static1.pt-content.com/images/pt/2013/08/IMG_20130818_171429_224-1.jpg


Everything still need a bit of tweaking and I need to reposition my camera differently, but here's a video of them in action for the first time.

New homemade wheel alignment tools in action - YouTube (http://youtu.be/O6k3TJEMsV0)

I think it will view better if I have the camera stationary, not stuck to the car and I need to find out if my digital angle finder has a back light. Also I'll figure out a better way to measure the toe change with more accuracy.

Notice the two pieces of laminate under the tires, had them kicking around...cut them up and they slide on each other real nice. Should be able to hang a tape measure across the front and back of the 1/2" steel rod to measure and set toe real easy by myself and can also measure camber pretty easily as well. If I can figure out a way to set the upright part of the tool in line with the ball joints (can't see them from the outside) I can measure caster with them as well.

Anyway, that's how my Sunday went, hope all or yours was good too.

[Norm Peterson]

Alternatively (and probably easier) just sweep the wheels from some known angle right to the same angle left, take the algebraic difference between camber readings taken at those positions, and multiply by a factor that depends on what that angle right and left was. Most of the commercially available camber gauges use ± 20° and a 1.5 factor is built into the caster vial, but you could also use ± 15° where the factor = 2.


Norm

[SSLance]

There has to be an easier way Norm, right? :naughty:

Some progress tonight. Got my drill rod and washers in today. After having the washers turned out to 0.475 ID I headed home to put the rods and washers in place. As Ron warned me, I had to ream out two holes on the driver side and one on the passenger side to get them all lined up in a row straight enough to get the rod through. After some finagling, I got the rod and washers in place. A couple of the holes could have used a bit more work, but since it's all coming apart and more work on the holes needs to be done, I left it for the night.

Some notes in case anyone else wants to do this on a metric chassis. The stock LCA bolts are 12 mm. I ended up with a 12 mm drill rod, and 7/16s case hardened extra thick (5mm) washers which we turned the inside out to 0.475 ID which is also the ID of the bushings in the control arms. The 12 mm washers I ordered first had 1 mm of play between the washers and drill rod which isn't acceptable.

Anyway, here's the pics of the rods in place.

https://static1.pt-content.com/images/pt/2013/08/DSC03220JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03222JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03223JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03224JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03225JPG-1.jpg




Also had some time to try out my new laser pointer to check the bump steer. I started at 26" fender height which might be where the ride height ends up, then dropped it by 1", measured, then 1" and measured, then raised it to 27" and measured. I had the graph paper up against the front of the inner fender and was using a marker and there wasn't any room between the marks, so I moved the graph paper up 7 feet in front of the car and remeasured.

7' in front of the tie rod ends, the toe moved out 3/4s of an inch with the 2" of suspension compression, and a 1/4" in with the inch up from ride height...and was the same on both sides. Someone better at math than me might have to help figure out how much it's moving at the tires...I know this though, it ain't much.

https://static1.pt-content.com/images/pt/2013/08/DSC03230JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03229JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03228JPG-1.jpg

That's it for now. Up next is the moving of the holes and welding the washers in place.

[Norm Peterson]

I've seen a sketch of a jig that would allow you to measure caster directly. IIRC, it registers off the ball joint studs - which has its own difficulties, including getting access to them without disturbing the wheels at all and ensuring that the jig is oriented specifically in a longitudinal plane (otherwise you'd be getting a mixed reading of cosine times caster and sine times SAI).

1/4" at 7' plus an assumed 6" for the steering arm length gives about an 0.042" difference if you were using dial indicators against the wheel flanges at 15" on center. You'll note that your data points do not lie in a straight line - this is to be expected. It's high, but not unexpected. I clearly remember having to saw away at the steering wheel of the Malibu to stay on line when encountering gentle pavement heaves in the middle of sweepers at only normal street driving speeds.


Norm

[SSLance]

Thanks Norm, I knew I could count on someone to do the math for me. ;) I moved the data lines down myself to give me room to write the fender height measurements on the sheet, The dot on the paper stayed at about the same height as it moved across.

I didn't have my GoPro out in the shop last night, I'll do this exercise again later while running the camera to show actual movement.

I forgot I picked up a dial indicator at a swap meet a few months ago, maybe I'll use it on the wheel to see how much it is moving there.

[Norm Peterson]

Double post, page didn't update properly for me.


Norm

[Ron Sutton]

Hey Lance,

You're doing a great job. I suspect you're learning a lot too & having a few "ah-ha" moments. Doing this "hand-on" is a great learning experience compared to talking about it or playing with computer programs.

You measured from the tie rod, which is "approximately" 6" behind the front of your tire. Therefore the math works out to approximately .090" toe change per 1/4" on your graph paper. So in 2" of dive (compression) your Monte is bumping out .180"

You & I are happy ... for now. I'll explain to everyone else why.

Everyone following along ...
Lance installed the bump steer kit with the rod end as low as it would go on what is called the "bump steer stud" that bolts into the spindle in place of the tie rod. The lowest position provides maximum "bump out". We did this, so we could check to see if we would have enough adjustment with the bump steer kit we choose. Stock production cars typically "bump in" ... meaning the steering gains toe-in on suspension compression. They typically bump in ... a lot.

When you tilt the spindle back ... to add caster ... you're raising the steering arm ... which increases the "bump in" ...making it worse if you don't fix it. So I knew we'd need to move the tie rod pivot down away from the steering arm more than most to achieve "zero bump" because of the higher caster Lance is running.

Right now, the car has about 7.5° of caster ... and the steering "bumps out" .090" per inch of travel. We would like to increase the caster to 9.5° ... which will raise the steering arm up even more ... about .227" or close to 1/4". This will reduce this "bump-out". We need to make sure it doesn't turn back into "bump-in". Our goal is zero bump steer change from ride height, compressing 2" or lifting 1". We'll go past this to see when it changes. But all that really matters is the suspension travel you're actually using in track conditions.

So Lance, lets do a brief "mock" bump-steer exercise to ensure we can get the bump steer to zero change through the travel area we care about. With no changes to the suspension ... take a small amount of shim from above the rod end & place it below the rod end ... raising the rod end up .... and re-run your laser test. For this exercise, converting the math is unnecessary. If you achieve zero bump steer on your graph paper ... 7' out ... you would have zero bump steer at the tire.

You don't need to futz with thin shims to get it to absolute zero at this point. We just need to see what will happen when you add caster & the steering arm raises .227". So one of your laser tests needs to be with the rod end up that amount. If your bump steer kit has a .100" shim & a .125" shim ... that is what you need to move from above the rod end to below it & test. If not, use a .200" shim or .250" shim to get us close.

I'd suggest doing this one shim at a time ... so you can see how this works, and within this range ... how much shim equals how much change ... I'd suggest you get there a shim at a time. Measure the shims each time & record it, so you know how much shim equals how much change ... and at what point does it go past zero bump & turn back into "bump in".

Post any questions if you're not clear.

[Ron Sutton]

I've seen a sketch of a jig that would allow you to measure caster directly. IIRC, it registers off the ball joint studs - which has its own difficulties, including getting access to them without disturbing the wheels at all and ensuring that the jig is oriented specifically in a longitudinal plane (otherwise you'd be getting a mixed reading of cosine times caster and sine times SAI).

1/4" at 7' plus an assumed 6" for the steering arm length gives about an 0.042" difference if you were using dial indicators against the wheel flanges at 15" on center. You'll note that your data points do not lie in a straight line - this is to be expected. It's high, but not unexpected. I clearly remember having to saw away at the steering wheel of the Malibu to stay on line when encountering gentle pavement heaves in the middle of sweepers at only normal street driving speeds.


Norm


How I did it came up with .045" roughly. But it doubles when measuring for toe-in or toe-out ... because you're measuring the difference in front of the tire ... .045" ... and at the rear of the tire ... another .045" ... to get to .090".

It could very easily be .042" +.042" = .084". I used 26" for tire diameter, but that was just a ball park too. I'm not worried about being super precise at this point, and I want to use methods most car guys are comfortable with.

[SSLance]

Sounds good Ron, I can do that. I can do this on just one side right, no need to do the passenger side too since it appears it is moving the same amount?


Regarding the work...it's pretty interesting...to me anyway. Most of the people I talk to about what I'm doing think I'm bat crap crazy, but they just don't understand. I'm a problem solver by nature, and I like projects. Once I start on something, I dig in like a bulldog and try to not stop until it's done. Each step along the way where I'm successful eases my mind and refreshes me for the next step. Getting the right size drill rod and washers was taxing me, I get uncomfortable when things don't go as planned and am anxious to get the ship righted as soon as possible. My mind was eased when that all went to plan last night...finally...

Now I just have to get the thoughts of taking a carbide bit to my lower control arm mounting locations correctly out of my mind and eased... :hmm: :help:


:fingersx:

[Ron Sutton]

Sounds good Ron, I can do that. I can do this on just one side right, no need to do the passenger side too since it appears it is moving the same amount?
Yes. For now, we're just ball parking it to make sure we'll have enough adjustment when we add caster.


Regarding the work...it's pretty interesting...to me anyway. Most of the people I talk to about what I'm doing think I'm bat crap crazy, but they just don't understand.
Well you might be bat crap crazy. The jury is still out. Haha :lol:

I'm a problem solver by nature, and I like projects. Once I start on something, I dig in like a bulldog and try to not stop until it's done. Each step along the way where I'm successful eases my mind and refreshes me for the next step. Getting the right size drill rod and washers was taxing me, I get uncomfortable when things don't go as planned and am anxious to get the ship righted as soon as possible. My mind was eased when that all went to plan last night...finally...
As a "virgin" to most of these processes & modifications ... you have done a great job ... not only doing this technical stuff ... but showing it for others to see.

Now I just have to get the thoughts of taking a carbide bit to my lower control arm mounting locations correctly out of my mind and eased... :hmm: :help:
Relax. Even if you grind too much here or there, it's all fixable.

:fingersx:

As a veteran of the process of correcting and/or modifying the LCA pivot axis, I'm telling you if you take your time & follow the instructions I'm about to post, it will all be good. I'll get a detailed outline about LCA pivot axis problems, corrections and modifications later today.

[Ron Sutton]

Correcting Lower Control Arm Geometry

We all know there are factory tolerances in production cars. An area that most car guys don’t think about are the actual frame mounts for the lower control arms (LCA). The area we’re talking about are the “buckets” or “receivers” in the front frame clip that the LCA bolts into. They have a hole on each side of the receiver for the bolt to pass through in two locations … and two receivers … so a total of 4 holes for each side.

If you draw an imaginary line through those 4 holes, that is the LCA pivot axis. Forget imaginary … run a solid, straight rod through those four holes and you can see it, touch it & measure it. If your car uses ½” bolts, get ½” quality straight rod. If your car uses 12mm bolts for the LCA like Lance’s ’85 Monte Carlo SS get 12mm rod.

81136

In my experience … the LCA pivot axis is “off” right out of the factory ... on most cars. They may get farther off if the car frame or clip had any tweaking from incidents.

That LCA pivot axis is important to the front suspension geometry in many ways. Very important … in many ways … and usually overlooked. The LCA pivot axis is probably off … meaning not true & not the same from side to side … in your car. It has a direct affect on the handling of your car. Lance’s car had one receiver bucket ¼” higher than the rest … affecting anti-dive, caster gain & roll center migration. This changes where the instant center of the control arms intersect that forms what is called the “swing arm.”.

If one side is off … this makes the “swing arm” lengths different from side to side. That will place the roll center off to one side … as opposed to being in the center where it belongs. This swing arm difference compounds when the car is driven on track & the body rolls in the corner. Lance’s front roll center was 9.3" to the left of center sitting statically in the parking lot. When he autocrosses it … on LH corners, the RC moved, or “migrated”, to 18.7" left of center ... which contributes to a higher degree of body/chassis roll angle on LH corners compared to RH corners. You can read more detail about this in Post #93 of this thread.

All we’re really talking about are the 4 holes that locate the LCA. They are important … but this area is basically pretty simple.

In my experience, I find these LCA mounting holes can be off in any of three ways.
1. Very common problem is all four holes simply don’t line up … meaning you have to force the second bolt in … and the LCA has some degree of bind friction. If you were to run a correct size rod through all four holes … often the holes don’t line up. The rod has to be forced in, or won’t go at all.

2. When you do run a rod through all four holes on each side for both LCA’s … the horizontal angles of the rod, which is equal to the LCA pivot axis … often don’t match. It is common for them to have differing horizontal angles, like Lance’s did.

3. When you do run a rod through all four holes on each side for both LCA’s … the angles of the rod in relation to the chassis centerline … occasionally don’t match. It is not uncommon for them to have differing angles relative to the chassis centerline. This affects lower ball joint location in the fenderwell, therefore tire & wheel location in the fenderwell … and overall wheelbase.

Let’s discuss in detail what each of these affect & what that means to the handling of the car.

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#1. If you can’t run a truly straight steel rod through all four holes & rotate the rod smoothly with no friction & no bind … how will the LCA rotate without friction and/or bind? It can’t. If you have to force the second bolt in … or “bend” the bushings in the LCA … to get the second bolt to go in the LCA … then the LCA has some degree of bind friction. If that’s the case … which is common … the LCA doesn’t move freely & easily. Some degree of force is required to move the LCA up & down.

This is bad. Way worse than the typical mechanic thinks it is … for high performance & track driving.

That bind friction means the LCA doesn’t respond to small degrees of force. This reduces the tires ability to follow small irregularities in the track surface. That means you have less grip with the front tires. This is not huge, but it is bad. Any reduction in front tire grip means your car is slower on track period. When races are won by seconds or less, .5 to 1% less front tire grip is a big deal.

That same bind friction also means the LCA doesn’t respond as quickly to larger degrees of force. There is a bit of lag. Again, this is not huge, but it is bad. Any slowing of the suspension means the tire is not following the track as well as it should. This really shows up on 7-post shakers where we’re looking at percentage of tire contact. Not being able to keep the tire following the track surface equals a reduction in front tire grip. Your car will be slower on track. Every little bit of front tire grip matters.

You need to have your LCAs pivot freely, without bind & with minimal friction. This is an easy fix, that I’ll outline later. When you have it right, the LCA should pivot super free.

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#2. When you run a rod through all four holes that mount the LCA … that is the LCA pivot axis. If you put an angle finder on the very top or bottom of the rod (in between the two receiver buckets) and look at it from a side view … that will give you the horizontal LCA pivot axis. Rarely are they 0.0°. The problem is less about what the angle is … and more about the angle being different from side to side. If one side is 1.2ۜ° uphill to the front … and the other side is 2.1° uphill to the front … you will have several suspension geometry differences from side to side.

The horizontal LCA pivot axis affects:
• Anti-dive
• Caster gain
• Swing arm length
• Camber gain
• Roll center location
• Roll center migration during suspension travel

Holy crap. You don’t want all of these things different from side to side on a street, road race or AutoX car. Yes, oval track race teams intentionally make them different from side to side, to help them achieve their specific goals turning left & only left.

Anti-Dive & Pro-Dive primer:
• The net degree of anti-dive or pro-dive the front control arm assembly has, is completely determined by the instant center formed by the UCA & LCA horizontal angles (side view). Both UCA & LCA horizontal pivot angles define this … not just one. So the LCA pivot angle is simply affecting the total.
• Simply put, if the instant center is behind the front axle centerline, the front control arm assembly has anti-dive. If it is in front, it has pro-dive. The longer the distance from the axle CL to the instant center … the less degree. The shorter the distance to the instant center, the higher the degree.
• The LCA pivot axis running downhill to the front adds anti-dive to the front control arm assembly. Uphill adds pro-dive … the opposite of anti-dive. Said another way, if the LCA is running uphill to the front … it simply reduces the degree of anti-dive.
• Anti-dive adds caster as the suspension compresses. This is known as caster gain. Pro-dive reduces caster as the suspension compresses. This is known as caster loss.

81135

You sure don’t want these different from side to side. Having less anti-dive on one side of the car will make that corner compress the suspension quicker & end up with less caster in dive. Having more anti-dive on one side of the car will make that corner compress the suspension slower & end up with more caster in dive. This means the car will have more roll angle turning one direction … and less roll angle turning the other. And … you’ll have caster split (difference in caster from side to side) making the car turn easier to the side with more caster & harder the other way.

Moving on to other problems …
With the two front control arm assemblies having different geometry … in additional to anti-dive & caster gain differences … you also end up with different swing arm lengths side to side … meaning you’ll have different camber gain on each side. The roll center location won’t start in the center … and it will migrate to different points during suspension travel & body roll.

To summarize … the car will not turn the same one direction as the other. As much as the final numbers matter … being the same from side-to-side is just as important. So you need to get the horizontal LCA pivot axis the same from side to side.

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#3. Most everyone has seen factory LCA’s and know they are longer on one end & have the pivot axis at an angle to the chassis centerline.

If you were to look from a top or bottom view of the chassis … and you have a rod through all four holes on each side for both LCA’s … the angles of the LCA pivot axis … in relation to the chassis centerline … occasionally don’t match side to side. They are typically around 14°. But if one side is 14.1° & the other side is 13.3° you may want to true that up. Why? … what does it affect?

81134

That angle plays a role in the location of the lower ball joint, therefore the steering axis of that suspension system. In my experience with factory clips, this can vary just as easily as the other angles being off from side-to-side. If one side is angled less, that moves the lower ball joint … and spindle, wheel, tire, etc … rearward in the fenderwell … shortening the wheelbase on that side of the car. (Assuming the rear axle is true in the car.)

Obviously, if the LCA on one side is angled more, that moves the lower ball joint … and spindle, wheel, tire, etc … forward in the fenderwell … lengthening the wheelbase on that side of the car. (Assuming the rear axle is true in the car.) Regardless of how you view it … if one is back or one is forward … if the front axle/spindle centerlines are not even … you will have handling differences.

What does this affect?
When the wheelbase of the car is different side to side … and the differences are in the front & the rear axle is square … the car will compress the suspension farther on the front corner with the shorter wheelbase.

Example:
With rear axle square in car … and the wheelbase is 108-1/4” on the left & 107-7/8” on the right … the car will be looser on LH turns & tighter on RH turns. Yup … might want to square this up. :)

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I’ll be back on today with a post on how to measure, how to correct & how to “improve” LCA geometry.

[SSLance]

Little more playing around with the bump steer kit.

With 0.2555 spacer below the rod end bump steer out 7 feet in front of the tire was as follows

.500" out at 24" fender height
.250" out at 25" fender height
.000" out at 26" fender height
.187" in at 27" fender height

https://static1.pt-content.com/images/pt/2013/08/IMG_20130820_192924_807-1.jpg



With 0.4710 spacer below the rod end bump steer out a 7 feet in front of the tire was

.250" out at 24" fender height
.000" out at 25" fender height
.000" out at 26" fender height
.000" out at 27" fender height
.187" out at 28" fender height


https://static1.pt-content.com/images/pt/2013/08/IMG_20130820_194942_326-1.jpg

Like Ron said, we are still going to add another caster which will raise the steering arm up, but it looks like we should be able to fine tune the bump steer pretty well with this kit (to my untrained eye anyway).

[Bryce]

If its a front steer it looks like the tie rod is too long. Any way to adjust the inner pivots easily?

[Ron Sutton]

Measuring, Correcting & Improving Lower Control Arm Geometry

We have three areas to work on:
1. LCA rotation
2. Horizontal LCA pivot axis
3. LCA pivot axis angle in relation to the chassis centerline

We have three possible goals:
1. Measure
2. Correct
3. Possible relocation for improvement

I am going to outline how to measure each of the three areas … how to correct all three … and potentially change angles for geometry improvement. Before you get started, you get clear on your goals. Are you looking to true everything up … for matching suspension geometry & even handing characteristics when cornering? Or are you looking to change geometry?

When Lance was measuring all the suspension points so I could calculate his roll center, camber gain, etc … he ran across one of the receiver buckets ¼” higher than the rest. I discussed what problems that causes … and showed him in the roll center graphs … and of course he wanted to correct it.

On the tuning front …
Lance already has the adjustable DSE UCA’s that added some caster, but he was maxed out at 5.7° currently. Lance wanted to make his car “capable” of up to 9.5° caster for AutoX competition. We planned to get this additional 4° through the LCA … which means you’re moving the lower ball joint forward. The calculations showed he needed to move the LBJ forward .800”+ to achieve this. I calculated that would move his spindle axis, tire & wheel forward about 9/16”. Since his tire & wheels were already located more than 9/16” behind the centerline of the fenderwell, this would be a double win.

The DSE lower control arms Lance chose are designed to move the LBJ forward by .400”. So we needed another .400”+. Given that Lance already needed to correct his LCA mounting holes … making the decision to get the additional .400”+ of LBJ forward movement by moving the LCA axis made the decision easier. Once Lance started this process, he found out his lower control arms had bind friction, as outlined in problem #1 in the previous post.

So Lance’s goals are:
1. Eliminate any LCA pivot bind friction
2. True up the horizontal LCA pivot axis if needed
3. Gain caster by moving the LBJ forward.

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Step-by-Step Plan:

Please read this thoroughly before starting, because it may prepare to do some things before you get started.

Parts & materials needed:
• Two 16-18” pieces of truly straight, solid rod of the same diameter as your LCA bolts
• Hardened Machined Washers – 3/16”+ Thick
• Machined washers can not be “sloppy” on the bolts
• LCA Bolts ½” Longer to account for the thick washers
• New lock nuts

Tools needed:
• Tape measures
• Level
• Accurate digital angle finder/inclimeter
• Removable masking tape & sharpie
• Jack, jack stands, stand shims
• Die grinder with small round burr
• Round file
• Sander or wire wheel to remove paint
• Welder

Tip #1: Leave the die grinder in the tool box until all measurements are captured & we’re clear on all the goals.

Tip #2: Whether you use a lift, or jack stands, the closer you have the car to ride height angle (rake) & level side-to-side the easier it is to keep angles clear in your head. If you can’t do that. Figure out what the rake of the car is on the ground … and check it in the air … and write down the difference & direction so you can refer back to it when your mind is cluttered with angles. :)

Tip #3: Whenever you measure angles … always write them down with a note next to them saying “raw number.” This means it was taken with the car in the air. Then also write in your notes … and add or subtract your correction number … to know the “corrected angle” if the car was at its normal rake angle for ride height. I can’t stress this enough to write the word “raw” or “corrected” next to the appropriate numbers. This will keep your head clear & reduce the required drinking later. :)

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Step #1
Run the rod through all four LCA mounting holes on each side of the car. If you can not easily slide the rod through the 4th hole … figure out which hole or holes you can modify the least to get it to slide through. At this point, if it is snug, that’s not a problem. But if it requires flexing the rod to go in, don’t do it. It will throw your measurements off. If you need to remove very much material … get clear on which direction you move the LCA for your goals & remove material in the direction that helps your cause … and allows the rod to slide in easily.

Tip: I have found taking a little off opposite sides fo the two inners holes to be easiest.

Step #2
Install the LCA’s with the rods instead of bolts & make sure they rotate freely. Using adjustable jack stands, shims, etc … support the outer end of each LCA to mock up ride height. If the car is in the air, or on a lift, you can simply put the LCA’s at the same angle (front view) that they were on the car at ride height on the ground.

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Step #3
Using a digital angle finder/inclimeter on the very top or bottom of the rods, capture & record the exact angle of each horizontal LCA pivot axis. Figure out the difference … and decide if you’re going to match them by modifying just one side … or modify each side a little to meet in the middle … or modify both sides to achieve a target geometry you want.

Reminder: Convert the angle degrees to be corrected with the car at the normal rake angle for ride height.

If the two sides are close … say the corrected left number is 0.8° uphill in front & the corrected right number is 1.1° uphill in the front … you may decide to modify just one side to match them up. Which one you choose to keep depends on your geometry goals. I usually want them level to the ground or running slightly downhill to the front … so we get more anti-dive & caster gain, as outlined in the previous post. So I would suggest the left 0.8° as your target & match the right side to it.

Frankly, if it was a race car or hardcore track car, 0.8° uphill wouldn’t make me happy. That reduces the total anti-dive & caster gain. For my cars, I would be adjusting both LCA’s to achieve a level horizontal LCA pivot axis … at minimum … or I may even get it running downhill going forward … to add to the total anti-dive & caster gain. In my NASCAR Modifeds, whether we used Impala or Chevelle clips, we ran the horizontal LCA pivot axis at 3.0° downhill going forward. That’s not a magic number for all set-ups, just what worked well with our high travel Mods.

Tuning Tip: If you know you’re going to need all the caster you can get … or you’re having a hard time achieving your total caster goal … now is the time to add some caster gain. Again, tipping the horizontal LCA pivot axis downhill going forward adds anti-dive & caster gain.

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Step #4
With the LCAs mocked up at ride height (or ride height angle) … you need to measure what I call the “X” & “Y” coordinates of the lower ball joints. Find & mark a spot on the frame to measure “out” from the frame to the center of the LBJ … and write it down. This is X. It is important that your X measurements be a true 90° … or as close as you can humanly get it … and/or exactly in the same spot from the frame on each side of the car.

Find & mark a spot on the frame or firewall to measure “forward” to the center of the LBJ … and write it down. This is Y. It is important that your Y measurements be truly parallel with the car … or as close as you can humanly get it … and/or exactly in the same spot from the frame/firewall on each side of the car. Now do the other side & compare the numbers.

I’m sure this goes without saying … except I’m going to say it. You want to be as accurate as you can be. Some tips are:
• Get a helper.
• Measure the same way all the time.
• Make sure the tape is level, square, etc.
• Don’t run the tape at an angle. Use a level or square.
• Have only one person read the tape.
• Take your time & do it with care. Rushing leads to errors.
• Double & triple check your numbers.

Don’t be surprised if the numbers from side to side are a little different. Be surprised if they’re the same.

Initially just compare the left & right side X numbers … then just compare the left & right side Y numbers. But when you decide what you’re doing think of the combined direction you need to move the LCA pivot axis to achieve both.

If the two sides are close on their X numbers … say the left side ball joint is 12-1/8” out from the frame & the right side is 12-3/16” … you may decide to modify just one side to match them up. If on the other hand, if the X numbers vary significantly … the left side ball joint is 11-3/4” out from the frame & the right side is 12-3/16” … you may still decide to modify just one side to match them up … or you may decide to create a target number in the middle and move them both to that target number in the middle. Which route you choose may depend on your track width or clearance goals.

If the two sides are close on their Y numbers … say the left side ball joint is 24-1/8” ahead of your measuring point … and the right side is 24-1/4” … you may decide to modify just one side to match them up. If on the other hand, if the Y numbers vary significantly … say the left side ball joint is 24-1/8” ahead of your measuring point … and the right side is 24-7/8”… you may still decide to modify just one side to match them up … or you may decide to create a target number in the middle and move them both to that target number in the middle. Which route you choose may depend on your caster goals … or location of the axle centerline, tire & wheel in the fenderwell.

Regardless of your geometry goals, the important thing is to get both sides the same-same-same in every aspect.

Tuning Tip: If you know you’re going to need more caster … or you need a little more or less front track width … now is the time to get it. If this is a race car or hardcore PT track car, I would take this opportunity to push the ball joints out … for a wider front track width (providing you have fender clearance) and to move the ball joints forward … enough to achieve the maximum caster you could dream of running. I make all my race cars have caster capability of 2.0°+ more than the KPI degree angle … just in case I ever need it.

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Step #5: The Ah-ha Stage!

Now you know where you are with all your measurements. Work out the math & decide your target numbers for each of the three items:
1. Target horizontal LCA pivot axis angle in degrees.
2. Target LBJ X location in inches.
3. Target LBJ Y location in inches.

81150


With these numbers:
Decide which LCA pivot ends you’re deciding to move … and which directions you need to move them … and combine the directions & amounts. If you need to move the front of the left LCA down 1/8” & inward 1/8” … you could go down & in at a 45° angle ..175” (close to 3/16”). Otherwise, if you grind down, then over, you’re removing unneeded material.

Most machined washers for this application provide a “band” around the bolt. Measure yours to see how wide that band is. If it’s 5/16” … I suggest not grinding out more than 5/16” with the hole in any one direction. If you have more to remove than the band width of the washer … it is ideal to split the amount of material removed from both receiver buckets … versus taking it all out of one.

For example: If you need to move the front of the left LCA down 1/4” & inward 1/4” … you could go down & in at a 45° angle .350” (close to 3/8”) … that’s wider than the band of your hardened washer. Instead of doing that, I suggest you go down & in at a 45° angle .175” (close to 3/16”) on the front of the left LCA … and go up & out at a 45° angle .175” (close to 3/16”) on the rear of the left LCA. Make sense?

If you have a small to moderate amount to remove … achieving it all in one receiver bucket is fine, as long as you don’t enlarge the holes so big the washer can’t cover them. Lastly, if you can achieve the same goal by working either the front or rear receiver bucket … the rear one without the crossmember is often easier to work with. Just sayin’

Washer Tip:
If you find you need to grind farther than the range we’re covering here, you may want to explore larger outer diameter washers. It is key to have the washers thicker than the receiver bucket material by at least 50%. I use 3/16” & ¼” thick washers with great success. Also, I have had grade 5 & grade 8 “stamped” washers wear the holes out of round over time. I have never had a problem with hardened washers changing shape.

Important: If you’re going to fully weld the receiver buckets to the frame where there are weld gaps … now is the time … before you start grinding on the holes. I suggest this. But if you try to do it at the end, it will cause bind issues.


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Step #6: Now the grinding begins.

Tools needed:
• Die grinder with small round burr. I prefer a ¼” burr.
• Round file
• Sander or wire wheel to remove paint
• Welder
• Tape measures
• Level
• Accurate digital angle finder/inclimeter

This is no big job. And it is not super sensitive either. You will end up grinding the holes slightly bigger than they need to be … because you’re not going to use the holes to support the LCA bolts anyway. That is what the 3/16”-1/4” thick, hardened, machine washers are for.

All we’re really talking about here … is enlarging these 8 holes just enough to achieve your target LCA pivot angle & ball joint placement goals. This is important … but the process is basically pretty simple. Once you know the direction & estimated amount of material to remove, get to grinding & filing.

Here are my tips:
• Again, don’t be in a hurry. That leads to mistakes and/or too much material removed.
• You don’t need the LCA in place for the horizontal LCA pivot axis angle … but you do for the ball joint measurements.
• You will need to remove & reinstall the LCA & rod often. Out to grind … back in to measure.
• Don’t get lazy and grind a ton without checking it.
• A helper assisting makes the day go a lot easier.
• Deburring the inside of the receiver buckets helps the LCA to go back in easier.
• I prefer to grind the hole on the inner side of the receiver bucket first … as needed to achieve the desired angle … then simply slide the rod through and mark the other side of the receiver bucket with a sharpie around the rod to show me where & how much to grind.
• It is ideal to remove a modest amount of material from both receiver buckets … than to just one.
• If you are removing the majority of material from just one receiver bucket … you may find you need to grind a little here & there on the other receiver bucket to get the rod & LCA to move where you need it to.
• When in doubt … take it out & check.

I can’t say this enough. Whatever numbers you’ve decided on … you will want make both sides identical.

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Step #7: Targets Acquired

When you achieve the:
• Target horizontal LCA pivot axis angle in degrees.
• Target LBJ X location in inches.
• Target LBJ Y location in inches.

Deburr the inside & outside of the receiver buckets. Then use a sander or wire wheel to remove the paint from all surfaces that will get welded. I do the insides too, just so I don’t have to breathe paint fumes in while I’m welding.

When you put the LCA & rod back together this final time before welding … install all the washers as you go. Then travel the LCA’s through their motion range to ensure there is absolute no bind or friction. If there is any, fix it now.

Double & triple check your measurements. When you’re confident they are right, it’s time to weld the washers in place.

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Step 8: Welding

With the LCA & rod in place … tack weld the thick, hardened, machine washers on 3-4 corners of the washer. Do all 4 washers … then travel the LCA’s through their motion range again to ensure there is absolute no bind or friction. If there is any, fix it now.

If there is no bind or friction:
1. Check your measurements again.
2. Remove the LCA & rod
3. Reinstall the rod
4. Weld up the washers.

Of course you’re going to travel the LCA’s through their motion range again … to ensure there is absolute no bind or friction. If there is any, fix it with a small hand file.

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You’re done with the mods. You can now repaint spots, & reassemble the suspension.

Final Tip: Do NOT crank down on the LCA bolts & nuts. Tighten them just enough to so the bolt doesn’t spin. The lock nut will hold the bolt in. But if you “crush” the receiver buckets you will create bind & friction in the LCA.


.

[SSLance]

Alright!!! Easy peasy sounds like... :poke:

Actually that all seems pretty much like I envisioned it would go. My main concern given my setup is how am I going to get the frame square and level and the LCAs at ride height repeatedly for accurate measuring. I think I've come up with a plan though, let me know what you think of this.


I'll use the 2 post lift under the frame rails in the center of the car, they are leveled up front to back and side to side now (I've already checked). I've also currently got 10.5" stands set under each tire. My thought was to take some 4x4 posts that I have leftover from a project and cut them to my ride height length at the front of the frame rails (taken when on tires on the drive on lift) plus 10.5" and set them upright under the front frame horns and set the car down on them. This way the 4x4s would be holding the front section of the frame at ride height while the lift is holding the rest of the car at ride height and the wheels would be on the 10.5" stands under them. Ride height before was 25 1/4" at the fender and we are shooting for it to be closer to 26" so maybe I need to add 3/4s" to the 4x4s to achieve the frame height I'm looking for.


The car wouldn't be sitting on the 4x4s for support, the lift would still be supporting the main weight of the car...they would just be holding the front clip up from flexing down under the weight of the hanging engine. I guess ultimately a set of extra tall jack stands would be ideal for this and I might explore that angle today as well. They might not be as easily set to an exact height though.

My other question is whether or not to leave the lower ball joint hooked to the spindle during all of this or not? It would be a lot easier to put the LCA in and out of the frame buckets if it was loose, but it would be a lot easier to make sure it is all at ride height each time if it was hooked to the LBJ and the tire was on the stand.

I have time scheduled tonight to get after this...wish me luck!! :fingersx:

[Ron Sutton]

Alright!!! Easy peasy sounds like... :poke:

Actually that all seems pretty much like I envisioned it would go. My main concern given my setup is how am I going to get the frame square and level and the LCAs at ride height repeatedly for accurate measuring. I think I've come up with a plan though, let me know what you think of this.
It's not necessary to have the chassis level. You just need to know what the angle difference is from how the car sits on the ground.

For example, let's say on the ground the car has a rake downhill to the front, and a digital angle finder on the front frame rail, near the suspension ... in a flat spot ... reads 0.8°. Then with the car in the air, on the lift, let's say it still has a little rake downhill to the front, and the digital angle finder in the same spot now reads 0.2° ... you know you need to account for a 0.6° difference when you're measuring the horizontal LCA pivot axis.

I'll use the 2 post lift under the frame rails in the center of the car, they are leveled up front to back and side to side now (I've already checked). I've also currently got 10.5" stands set under each tire. My thought was to take some 4x4 posts that I have leftover from a project and cut them to my ride height length at the front of the frame rails (taken when on tires on the drive on lift) plus 10.5" and set them upright under the front frame horns and set the car down on them.
That's not necessary.

If you can "lock" your lift at a good height to work it, you don't need anything to support the frame. You do need something to support the LCAs at the same angle (front view) as ride height ... for the whole process.

This way the 4x4s would be holding the front section of the frame at ride height while the lift is holding the rest of the car at ride height
That's not necessary.

and the wheels would be on the 10.5" stands under them.
The front wheels need to be off for this entire process.

Ride height before was 25 1/4" at the fender and we are shooting for it to be closer to 26" so maybe I need to add 3/4s" to the 4x4s to achieve the frame height I'm looking for.
You don't have to work at the exact ride height you're shooting for. You just need to pick a number that is close. But it has to stay the same throughout the process.


The car wouldn't be sitting on the 4x4s for support, the lift would still be supporting the main weight of the car...they would just be holding the front clip up from flexing down under the weight of the hanging engine.
That's not necessary.

I guess ultimately a set of extra tall jack stands would be ideal for this and I might explore that angle today as well. They might not be as easily set to an exact height though.
That's not necessary.

My other question is whether or not to leave the lower ball joint hooked to the spindle during all of this or not?
The spindle needs to come off.

It would be a lot easier to put the LCA in and out of the frame buckets if it was loose, but it would be a lot easier to make sure it is all at ride height each time if it was hooked to the LBJ and the tire was on the stand.
That's why you need a support under the outside end of the LCA ... to ensure it sits at the same height throughout the process.

I have time scheduled tonight to get after this...wish me luck!! :fingersx:

Your message reads as if you're using techniques to accurately recreate ride height & measure suspension points ... like you did when measuring your front suspension geometry. That's not necessary here. It doesn't need to be that complicated. Keep it simple.

You got this Lance!

[SSLance]

Alright, that helps... I can lock the lift and leave it set. I have one tall screw jack I can use to hold the LCA in place. I can probably use a floor jack and a 2x4 for the other side.

I'll just have to find an easy spot to measure the LCA against the frame at ride height so I can reproduce that LCA angle with the car up in the air.

Maybe I'll take those 24" jack stands I bought this morning back to harbor freight and pick up another screw jack...

[SSLance]

I've got an idea...how about I just get a strong piece of wire (or plumbers tape maybe) and hook it in the sway bar mounting hole on the LCA and somewhere on the frame when the car is sitting at ride height. Then every time I put the LCA in with the car in the air, just hook that strap or wire back up and it'll hang the LCA in the exact same spot every time?

[Ron Sutton]

I've got an idea...how about I just get a strong piece of wire (or plumbers tape maybe) and hook it in the sway bar mounting hole on the LCA and somewhere on the frame when the car is sitting at ride height. Then every time I put the LCA in with the car in the air, just hook that strap or wire back up and it'll hang the LCA in the exact same spot every time?

That may work. I'm more a fan of something solid under the end. But that's your call & I'll let you figure that stuff out.

Post pics when you're done & let me know if you have questions along the way.

[SSLance]

Heck, if I can tie the sway bar up somehow, I can use the actual sway bar attaching links...just slide the bolt in the hole on the LCA each time.

This might even help more to keep the sides even if I can get the links both the same length.

I've looked for another screw jack locally and that isn't happening, so I need to figure another way to hold both LCAs up.

[SSLance]

Your message reads as if you're using techniques to accurately recreate ride height & measure suspension points ... like you did when measuring your front suspension geometry. That's not necessary here. It doesn't need to be that complicated. Keep it simple.

You got this Lance!


https://static1.pt-content.com/images/pt/2013/08/DSC03237JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03238JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03239JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03241JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03242JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03243JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03246JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03248JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03253JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03254JPG-1.jpg

I'm freaking physically and mentally wore out...

It all went pretty well though. Didn't set anything on fire and met almost all of the laid out goals. Please don't give me too much grief about my welds, I was much more concerned about making sure they were burnt in well than making them pretty. Plus I don't have near as much proper welding attire as I should have, especially for welding above my head. If one could do this with a stripped down frame without tie rods and other various parts in the way, it would be much easier to get the correct angle on the welding wire to pretty up the beads.

[Ron Sutton]

I'm freaking physically and mentally wore out...

It all went pretty well though. Didn't set anything on fire and met almost all of the laid out goals. Please don't give me too much grief about my welds, I was much more concerned about making sure they were burnt in well than making them pretty. Plus I don't have near as much proper welding attire as I should have, especially for welding above my head. If one could do this with a stripped down frame without tie rods and other various parts in the way, it would be much easier to get the correct angle on the welding wire to pretty up the beads.

Haha. You did great.

When you "recover" ... post the specs & measurements of what you did ... and why ... so everyone following along can learn.

[SSLance]

The hole movement goal was two or three fold... First the passenger front bucket holes had to go down to get the pivot angle the same as the driver side. Then the back bucket's holes on each side went out and the front bucket's holes on each side went in with the goal being to push the lower ball joint forward 0.400" than it was before while maintaining the exact same distance to the center of the frame.

We ground out the holes using a carbide bit on an angle grinder. Grind a bit, measure...grind, measure, grind measure...until we had the rods on both sides where we thought they needed to be. On several of the holes we could see the gap of the original hole past the edge of the washer. I was a bit unsure if I'd be able to fill that gap successfully with my limited welding skills so we stopped. At this point part of me was wanting to go all out and really move the holes further to gain every bit of potential caster, but my cautious side didn't want to create more problems with trying to get the washers welded in solid.


Then it was time to weld. We did the outer two washers first to get the rod set in place. Tacked them in, removed the rod, welded the washers solid, reamed the washers out a bit as they closed up and the rod wouldn't go back in...then put the rod back in place, tacked the inner two washers in place, removed the rod, welded the washers in, then opened them up so the rod would go back through all four washers tightly, but would still spin. Spatter would get on the rod when tacking which made it difficult to remove the rod each time because the washer to rod clearance was so tight. We found we had to file or grind the spatter off before removing the rod or risk breaking the tack welds on the washers driving the rods back out.

Hind sight, it wasn't that difficult to fill the gaps...I probably could have moved the holes a bit further and bridged that gap...but I just wasn't sure of that at the time. I was most concerned about blowing through the somewhat thin frame with the welder, but honestly, that never even came close to happening.

It was a long tedious process. We achieved most of the goals set out for us. We did the driver side first as the holes just needed to go sideways, not up and down. On the passenger side, we were tired, punchy, and needed to get it done as it was getting late and we just couldn't quite get the rod where we had the wheel base number AND the pivot angle number we were looking for. I made the call to get the pivot angle set to match the driver side but the ball joint ended up about 1/8" back from where the driver side is and the center out measurement is dead on. 2 out of 3 ain't bad I guess. We were tacking the washers in place when we discovered we couldn't quite get the rod exactly where we wanted it to be. We would have had to step back and go back to grinding some more to get it there and there wasn't enough time or motivation left to get that done at that point.

Hopefully we got it good enough and the UCA adjustments can mask the little bit of wheelbase difference. It has to be a BUNCH better than it was before as the pass side LBJ was a 1/2" in and a 1/4" back I think as well as the pivot angle being .4 degrees different than the driver side.

[SSLance]

Had the local photographer look back through his pics from our last event and he found these...

Before front sway bar and rear springs (taken last fall)

https://static1.pt-content.com/images/pt/2013/05/kcrscca_10072012_078-1.jpg

After front sway bar and rear springs were installed (taken 2 weeks ago)

https://static1.pt-content.com/images/pt/2013/08/DSC03260JPG-1.jpg


https://static1.pt-content.com/images/pt/2013/08/DSC03261JPG-1.jpg

Before...

https://static1.pt-content.com/images/pt/2013/03/kcrscca_10072012_043-1.jpg

After...

https://static1.pt-content.com/images/pt/2013/08/DSC03262JPG-1.jpg



There was 2.25" rake front to back during the last event which was a bit upsetting to the car. After my latest changes this weekend, that will change to about a 1.25" rake. That along with the much improved front geometry and improved front lower control arms should make even that much more difference in the car's cornering.

Can't wait...

[SSLance]

I've been making a little bit more progress since my last update...

Inside the frame pockets for the front coils, there were spring cups bent down at the factory to hold the top of the coil spring in place. These kept the Afco spring adjuster from sitting flat against the top of the inside of the frame. They had to go...

Before

https://static1.pt-content.com/images/pt/2013/08/DSC03256JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03257JPG-1.jpg

After some trimming and bending...and some paint to prevent rust

https://static1.pt-content.com/images/pt/2013/08/DSC03267JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03268JPG-1.jpg

Afco Spring adjuster welded in place.

https://static1.pt-content.com/images/pt/2013/08/DSC03269JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03272JPG-1.jpg

Then the control arms were bolted into place one last time. I put a layer of grease on the bolts before installing and slowly tightened them down just until they started to impede the free movement of the control arm, then backed them off just a touch. There is zero slop in the bushing area yet the arms swings easily throughout their movement.

Pics of the LCAs in place.

https://static1.pt-content.com/images/pt/2013/08/DSC03276JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03275JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03277JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/08/DSC03274JPG-1.jpg

Then it was time to fine tune the bump steer

I ended up with 3/16s" of spacer below the rod end on both sides and the rest of the spacers above and here are the results.

https://static1.pt-content.com/images/pt/2013/08/DSC03280JPG-1.jpg

These measurements were taken 91" in front of the contact patch of the front tires. Ride height goal is 26.25" at the fender, I measured the bump steer 1 inch above ride height and 1 and 2 inches below ride height (dive).

Ron and I were on the phone back and forth throughout the adjustments...he was diagnosing my pics of measurements and advising me what to try next from 2 time zones away. I thought that was pretty cool of him.

It got late and I sent him this last picture and said I was hitting the shower. I think it's as good as we are going to get it, I know it isn't perfect but around 3/16s of an inch of bump out 91 inches in front of the tire at full dive, I'm hoping that is driveable anyway.

Next up is to get the coil springs back in the car, hook up the sway bar and bump stop, nut and bolt everything one more time, load on the trailer and take it to the alignment shop. The shop has time available tomorrow, hopefully I'll get the car buttoned up tonight and to the shop.

[Ron Sutton]

Hi Lance,

Doing the math, whatever difference you see with the laser pointing at 1/4" graph paper 91" away ... is exactly 3.5 times less when measured at the tire.

So ...
1/4" (.250") on the paper is .071" of bump steer change at the tire.
3/16" (.187") on the paper is .054" of bump steer change at the tire.
1/8" (.125") on the paper is .036" of bump steer change at the tire.
* By doing it this way ... which amplifies the differences ... it's easier to see changes & way more accurate.

While we could make many various combinations work, what I'd like to see you start with is:
Static toe-out of .060-.066" total / .030-.033" per wheel
Toe-out gain (aka "bump-out") .070"-.090" total / .035"-.045" per wheel at 2" of dive.
Dynamic toe target: .130" to .156" toe-out in dive.

You got it to here in your 2nd to last attempt.

81431

This was very close to zero bump steer & would be considered almost perfect for most street cars. Unfortunately it was had a tick of "bump in" (slang for bump steer achieving toe-in when the suspension is in dive (compressed like it does under braking & cornering).

Since you autocross the car, we need a bit of toe-out in dive to help with initial corner turn-in response and to optimize the inside tire slip angle. We needed to add approximately .015" -.025" of shim above the tie rod end.

But since you only had a .065" shim to work with, it changed it too much & ended up like this:

81437

This works out to about .200" on the graph paper 91" ahead ... and about .057" at the tire ... per side ... for a total "bump out" amount of .114". that could be made to work with less static toe-out, but instead I'd suggest this ...

For now, take the .065" shim back out ... get the car back to "almost zero bump steer" ... like you had in your 2nd to last attempt.

Get the front end aligned & geometry set & go run it.
Before you go to the track, by yourself some 5/8" ID shims in thicknesses of .010" to .015". At the track, add .010" bump shim above the rod end after your baseline runs. See how you like it. Keep adding shim as long as it improves turning ability. Stop & back up one shim if you go too far.

Here's why to do this way. No one can tell you exactly how much dynamic toe-out you need to achieve the optimum slip angle for your car & tires, unless they have tested the exact same set-up. Testing is the only way to know. The cool part is all you need at the track is a pad to lay on, a 5/8 ratchet & the shims. :)

[Ron Sutton]

Hi Lance,

My suggested starting point for your "static" front end geometry settings is:
Camber: -1.3°
Caster: 8.5° ... if you can get it.
Toe-out: 1/16" total ... 1/32" per side.

[SSLance]

Couple of quick lessons to pass along to the class. First, geometry is hard...especially if you are in a hurry. Second, things very rarely go as planned. And if anyone else attempts tack these Afco spring adjusters in place in your frame pockets, make sure they will clear the shock absorber after tacked in place. :secret:


After cutting out and repositioning the pass side adjuster last night, I proceeded to compress a spring and put it in place. I knew the fender had to go up 1" so I carefully measured the adjuster flange so that it was 1" lower than the frame pocket and compressed the spring a little over an inch to give me some leeway. Once I had the spring in place and the ball joint tight, I could not get the compressor out because the top tangs of the compressor were stuck against the adjuster. Out it all came once again. One the second try, I couldn't get the bottom wedge of the compressor out because it was jammed against the LCA spring bucket. On the the third try, I realized I only had to grab the middle 3 rings of the coil spring making not only the spring easier to compress but a TON easier to get out once the spring was in place. Somewhere along the line of this I also discovered that my tie rod end separator will not reach to break apart my tall ball joints, something I have to figure out a better way to do for sure. Anyway on the third attempt I got the spring in place and the compressor out. On to the passenger side.

This went pretty easy as I now have the procedure down pat. Then I buttoned everything else up hustling because I need to get the car down and on the trailer as I have a 9 am appointment at the alignment shop. Sway bar ends, bump stops, shocks, and finally tires installed and snugged down.

Set the car down on the ground, freaking fenders are at a tad over 27"... :banghead: :machine: :hammer:

I knew right away what I did. And I knew damn well that 1" at the shock was good for about 2" at the fender because I had documented all of that while measuring for shock travel. It just slipped my mind while hurrying to get this done last night. Needless to say, I was PISSED... I back the car out for a quick spin around the block anyway just to see if the steering wheel was pretty straight and if it would settle any at all once compressed a few times. Right away I noticed it wasn't steering right and headed back to the garage. Further inspection revealed that my tie rod ends are now firmly up against my sway bar. :banghead: :machine: :hammer:

Last time I test fit this all was before the pivot hole relocation and the bump steer adjustments, both of which raised the tie rods enough to interfere with the sway bar.

At this point, the shop is trashed, I'm trashed, and I'm in no mood to fight it anymore. So I punted...

Sometime in the future when I've calmed down and am not trying to hurry anymore, I'll pull the front springs AGAIN and readjust the adjusters properly and figure out a way to extend my sway bar links...then head to an alignment shop to work on the settings Ron posted above. None of this is a death blow, but it can work on one's state of mind. I need to recharge and hit it again later. I guess this is the difference between bolt in suspension kits and custom suspension work. I fully respect what the big companies that develop these bolt in kits go through during this process now. And I still like the way I am going about this and have learned a TON while going through this school of hard knocks. These lessons are the type you don't forget.

[SSLance]

Hi Lance,

My suggested starting point for your "static" front end geometry settings is:
Camber: -1.3°
Caster: 8.5° ... if you can get it.
Toe-out: 1/16" total ... 1/32" per side.




Car is on the trailer, appointment at the alignment shop at 1 pm.

Wish me luck...

[Ron Sutton]

Cool! Text me if you have questions.

[SSLance]

Trip to alignment shop went well. We re-set the rear thrust angle and pinion angle, then moved to the front and got as much camber and caster as well could get out of the passenger side, then made the driver side match it and set the toe.

Car drives out nice, no shimmys shakes, vibrations, or pulls. Tracks great... No sign of any bumpsteer. Didn't get too aggressive as still no front sway bar end links, they are built though, just need bolted on.

Here's the new stance

https://static1.pt-content.com/images/pt/2013/09/IMG_20130904_185353_308-1.jpg

Lance is happy, now off on vacation for a few days. Will post all of the specs achieved when I get back.

[SSLance]

So, here's the sheet with the new alignment specs

https://static1.pt-content.com/images/pt/2013/09/Alignmentspecs09042013_Page_2a-1.jpg

We were aiming for more static camber and caster, but the back upper control arm bolt on the passenger side was too short to give us the settings we wanted. Had a couple of texts back and forth with Ron while the car was on the rack trying to decide which way to go, more camber or more caster, as we had a little bit of play room with the front UCA bolt on the passenger side and we settled on this.

We then set the driver side to match the passenger side and set the results you see above.

Here are my newly extended sway bar end links (with the old standoffs next to them).

https://static1.pt-content.com/images/pt/2013/09/IMG_20130911_132618_354-1.jpg

I'll get these installed in the next day or so and do a little data acquisition with my Gopro mounted under the car to help get them set in the right place where the sway bar won't contact the tie rods and yet the ends will be set as parallel to the ground as they can be.

[Ron Sutton]

Looking Good!

Don't you have an AutoX event coming up soon ?

[SSLance]

Sunday SUNDAY Sunday!!!

:git: :drive: :woot: :fingersx:

[SSLance]

Alrighty then...

Barney is back down on all fours, all suspension components have been firmly reattached in the appropriate positions and more importantly...are not hitting each other anymore...

Test drive in the dark last night was successful... All it needs now is a bath and an event to go to.

Lets go racing!!!!

[Ron Sutton]

Cool. Have fun racing. Give us a complete update when you get back !

[SSLance]

So I drove the car to work today, first time on an extended highway run since all of the latest changes. I must say, the car drives fantastic!!


Not even a hint of bump steer feedback, car drifts just a tad to the right in the right lane and a tad to the left if in the left lane (following the crown of the road), no heavy feel to the steering even in parking lots, no vibrations, and just a real nice tight feel to the springs and shocks. Nothing jarring, or heavy feeling at all. I don't notice any more NVH inside the car now with all of the delrin in the front than I had before with the rubber bushings. I wouldn't hesitate to get in this car and drive it across the Country now...that makes me very happy.


When it was on the alignment rack, we spent quite a bit of time dialing in the rear control arms. We squared the rear end up as good as we could get it with the LCAs and then adjusted the UCAs to set the pinion angle exactly parallel with the trans output. This completely eliminated the pinion vibration that was evident after raising the rear ride height. 1.5 degrees of pinion angle change is more than enough to create a vibration...and the pinion angle will change that much with an inch of ride height change making it mandatory IMHO to put adjustable UCAs on any G-Body with any sort of ride height change.


I didn't hit any fast curves on the way to work, it's mostly a straight shot of highway, but I did have one slow speed exit that I played a bit on. It is amazing how this car corners now. The front is absolutely stuck, I haven't found the limit of it yet. And the rear is a bit loose but with just the right amount of throttle input, it squats down and is planted as well.


Ron coached me a bit on the phone yesterday with how to drive the car with this setup. He stressed that I need to be easy on entry, early and smooth on the brakes, then equally smooth on throttle input once the car is set in the corner while trying to maintain as much speed as possible in the turn. He says it's hard to believe this, but if the rear is loose, you can actually get it to grip by applying throttle which will transfer weight to the rear and make the rear tires grip better. I plan to put all of that to the test this coming Sunday.


In the meantime, I'm just enjoying driving the car. I'm very happy that none of these changes have disturbed the road quality experience of the car and in fact have helped the driveability. I wish all of you could go along on a ride with me to check it out.

[SSLance]

Rain... :banghead:


After making a bunch of changes to the car I really wanted to feel it out, but my first two runs were wet yesterday, which was treacherous at best. It dried up a bit for the third run and a bit more for the fourth, but by that time I was trying too hard to beat the WS6 and 2011 Camaro I was racing directly against and blew my runs.


I would have beat them both if not for the cone I hit after my last trip through the timing lights at the end of the course, spun it out trying to get that last little bit.


I went out first each run, the Camaro was 4 cars behind me, the WS6 2 cars behind him


2000 Pontiac Trans AM WS6 Blue 69.095 65.660 60.466 59.739 59.739
2011 Chevrolet Camaro White 70.995 66.881 60.108 59.896 59.896
1985 Chevrolet Monte Carlo SS Maroon 70.482 67.790 60.054 59.064+1 60.054




Not only that, but my camera quit talking to my phone for some reason and due to operator error, I ended up just getting stills on my last two dry runs, not any video, so I really don't have any data relating how the suspension is working either.


http://youtu.be/AbbGNxu110U


I'm gonna run my slicks again at an autocross in two weeks, so I'll have the same traction at both ends. Hopefully that along with getting my GoPro to play nice again, will let me get a better feel for how all of the changes actually work on the track.

The car desperately needs new street rubber on the rear rims...but I'm holding out to see if BFG comes out with a 275/40/17 Rival before picking any up. Can't really tell how the car is working with brand new Rivals up front and wore out Nitto 555s out back.

I think it's gonna be good though. The front is definitely hooked up, even in the rain I never slid the front tires. Back end was all over the place though, couldn't keep it straight.

[Ron Sutton]

Thanks for the updates. Sorry for the rain.

The real test will be when you have good rubber front & rear.

[SSLance]

Yeah, I really feel like I never got the chance to see what the car can do yesterday. Even as it dried up on the last two runs, the asphalt part (where the slalom was) was still treacherous. Just when you thought it was dry enough for some grip it would lose traction completely...that led to an uneasy feeling and erroring on the side of caution while at the same time trying to go as fast as you could as your chances were running out.

Not a good combination.

When I last ran the car on street tires early this season, it would push the front tires in the corners and create the havoc I was dealing with when I started this thread. Even in the rain yesterday, it never pushed the front once. The front is really hooked up and it sure seems to not be rolling near as much as it was before. When driving the car on the street, it really feels balanced front to rear. The other night I was taking 35 mph corners on the 2 lane road at 75-80 mph and it felt fantastic. The front went where I pointed it and the back would set in yaw just a bit then just stay planted. Before in those corners at that speed the fronts and the backs would be squealing for help and this time they never made a sound. I can't wait to see what the car does in dry conditions with equal rubber on the front and the back. Hopefully we get that situation at our next event in two weeks.

[Ron Sutton]

When I last ran the car on street tires early this season, it would push the front tires in the corners and create the havoc I was dealing with when I started this thread. Even in the rain yesterday, it never pushed the front once.
Awesome. That was out goal.

The front is really hooked up and it sure seems to not be rolling near as much as it was before.
Those go hand-in-hand with your new "Tweener High Travel/Low Roll Suspension."

When driving the car on the street, it really feels balanced front to rear.
Excellent. When you get equal tires front & rear on the car, it will be pretty balanced at the track too.

The other night I was taking 35 mph corners on the 2 lane road at 75-80 mph and it felt fantastic.
Nice.

The front went where I pointed it and the back would set in yaw just a bit then just stay planted.
I know it seemed like we went up on the rear spring rate a lot ... and we did. But I calculated the FLLD & RLLD numbers and knew it would help keep both left side tires planted for more total grip. Remember, on spring rate, we went a tick on the free side.

Readers: Lance had 125# rear springs. When I ran the calcs to achieve the balance we needed with the new front sway bar, the optimum spring rate came up at 207#. I asked Lance if he wanted to err on the side of tight or loose & he choose loose. So we went with 225# springs. I think this will fastest for AutoX, but it will be on the edge of "free".

Before in those corners at that speed the fronts and the backs would be squealing for help and this time they never made a sound. I can't wait to see what the car does in dry conditions with equal rubber on the front and the back. Hopefully we get that situation at our next event in two weeks.

I'm looking forward to hearing how it goes too !

[Mizzouri]

The slalom and that back sweeper were still slick on the 4th run. I had to laugh as the 3rd heat guys had full dry pavement, and their times reflected it.

I'm ready to spend all next season going head to head! Now where did I put those 315s........

[SSLance]

I'm looking forward to hearing how it goes too !


Well, yesterday's event was a whole different story with the new setup. In order to make things easier to grade, I bolted my Hoosier A6s back on the car and ran in Street Modified for this event. This gave me equal tire grip on all four corners of the car.

I also booked to run in two heats, so I worked heat 0, ran heat 1, ran heat 2, then worked the course in heat 3. When you do this, the second heat's runs don't count towards your score, but you are still timed and get to see if you can better your time as you run. I used the extra runs to more familiarize myself with the new setup and to give some ride alongs at the same time.

The course design played right into my hands...it was beautiful if you were driving a "ground pounder" type of car. 3 straights with speeds in the 60s on all three...with just enough turns in it to make it interesting.

Here was the in car video from my 7th run of the day which was also my fastest. My passenger was the Co-chair of the event and also the course designer.

http://youtu.be/jZQiX6p-ELE

Here were my times for the day:

Heat 1
#1 53.123 (hit a cone on the inside of first sweeper, was surprised how well it turned)
#2 52.438
#3 52.307
#4 50.260 (last one that was going to count, so I stepped it up)

Heat 2
#1 50.232
#2 49.820
#3 49.553
#4 50.123 (over drove the corner after the last straight, wheel hopped under braking and dirttracked the corner)

Here are the posted raw time results

http://www.kcrscca.org/results/solo/2013/2013_event11_raw.htm

Officially I finished 25th out of 100 drivers. Had my 49.553 counted I would have finished 18th.

Check out the list of cars I finished ahead of! A LOT of those cars are considered "autocross" type cars and a bunch of them were running on some sort of racing compound tire as well. This was done with my 3700 pound 1985 Sport Luxury Monte Carlo with a full interior including AC! Nothing better in my book than beating them at their own game.

Here are my tire cam videos and my best run again, it's worth watching to the end just to hear the announcer talk about my runs. They are starting to notice me more and more now.

http://youtu.be/N3ggkP3P_tE

I'll let Ron talk about the changes we've made and how they've affected the car from his perspective...I LOVE them and think it can only get better. It's unbelievable the grip this car has now, even with the problems it still has which we will continue to correct upon.

[SSLance]

Some still shots from yesterday

Doug, our Co-Chair is also our photographer...so he didn't get to take any pics this weekend. My wife and Mom got some from the sidelines though...

Here's one where SSLance was giving Monte Carlo all it had in the hard 180 after the back straight...

https://static1.pt-content.com/images/pt/2013/09/DSC03718JPG-1.jpg

Bit out of focus, but diving into the same corner a few runs later...

https://static1.pt-content.com/images/pt/2013/09/DSC03723JPG-1.jpg

Accelerating hard out of the first corner after the start

https://static1.pt-content.com/images/pt/2013/09/DSC03721JPG-1.jpg

Pretty hard on the binders here into the sweeper before the back straight.

https://static1.pt-content.com/images/pt/2013/09/DSC03716JPG-1.jpg

The car turned so well in that corner that I hit a cone on the INSIDE of the corner on my first run. I usually really struggle in that corner as the pavement is giving up there, not yesterday though, was able to just power through and build up speed for the back stretch.

Hard on the gas heading into the walloms on the back stretch

https://static1.pt-content.com/images/pt/2013/09/DSC03742JPG-1.jpg

Coming out of the last wallom on the back straight setting up for the hard 180 to the right.

https://static1.pt-content.com/images/pt/2013/09/DSC03737JPG-1.jpg

Setting up for the third straight on my fastest run of the day

https://static1.pt-content.com/images/pt/2013/09/DSC03738JPG-1.jpg

Same run, last turn before the finish...

https://static1.pt-content.com/images/pt/2013/09/DSC03739JPG-1.jpg

Last run of the day, last corner at the end of a straight...

https://static1.pt-content.com/images/pt/2013/09/DSC03744JPG-1.jpg

Over drove it for the first time of the day, wheel hopped, slid, then muscled it on through. Cost me a half second.

[SSLance]

So, after a couple of days rehashing the day at the track and the way the car handled after all of the changes, I found myself thinking about the places I left time on the track. In a couple of the pictures I posted above, you can see that I was sliding the front tires at different times in the 180 right hander at the end of the back straight. Knowing that I had video of this happening, I decided to slow the video down to half speed to make it easier to see exactly what was happening and try to figure out how to keep from repeating it.

Here is the slo-mo of what I'm talking about.

http://youtu.be/zFRhfKQVyZw

At about 10 seconds in, you can see the front plant pretty hard under braking, then during turn in all seems good.

At about 14 seconds...the fender starts to raise back up off of the tire right at about the middle of the turn. This is when the right front tire looses grip and slides...

Thinking back the front probably came up as I let off of the brake pressure as I had slowed enough for the corner. The car was also rolling over at the same time.

I'm certain there are mechanical things I could do to the car to keep this from happening (stiffer sway bars, better shocks with slower rebound to hold the front down longer) I'm wondering though if there are driving tips that could help me get through a corner like this without sliding the inside front tire? Timing wise, is there something I could have done differently to still carry maximum speed through the corner but keep the inside front tire from loosing grip when the front becomes unplanted?

[Norm Peterson]

I doubt you've got enough aero effects to where front ride height is sensitive enough to matter at maybe 40 mph, so I think that trying to tie the front down with shock damping might be counterproductive (more rebound damping will lift more load off the inside tire faster during that upward motion than the upward position suggests). More rebound in the rear shocks might be something to try if the car is understeering when you are not sliding a tire like that.

What I think was happening is that you carried a little too much braking a little too deeply into the turn. Eventually the combination of braking traction plus lateral acceleration and the accompanying roll and upward force from shock rebound was more than that tire could handle. So it locked at least partially and made the front slide. The smoke begins to be visible just before 0:14.


Norm

[SSLance]

Thanks Norm, was wondering if you had seen the results and videos from my last event yet.

Not sure that it makes any difference but I was up into the mid 60 mph range at the end of all 3 straight stretches on that course. It was really giving the low horsepower cars fits...most of them were shifting 6 times or more during a run.

You should have seen the grin on my face get bigger and bigger as I walked the course for the first time...and then after each run.

I'm wondering now if I shouldn't have braked harder while keeping the car in a straight line and then entered the corner much later (late apex)? This way I would have been completely off the brakes mid corner and if set up properly could have gotten back to the gas faster. The pinch point in that corner was the cone on the outside entering the next straight. If I had used a later apex line, I might not have needed to use as much steering input at that point where I slid the inside front tire.

It was hard to stay out as long as I did though, carrying that much speed and knowing how tight of a 180 turn it was...it was like it sucked me into the turn early on just about every run.

[SSLance]

Oh, I should add, the only time the car understeered all day long was in that particular corner a couple of times...when I was locking up the inside tire. The rest of the time the front was stuck.

So much so that in the first run, on the first big right hand sweeper...I hit a cone on the inside because the car turned so much better than I thought it might and it surprised me. I just keep adding speed and adding speed each run after that and it just kept on sticking.

[Norm Peterson]

Oh, I should add, the only time the car understeered all day long was in that particular corner a couple of times...when I was locking up the inside tire. The rest of the time the front was stuck.
How did the rear feel relative to the front? Docile, like it'd never step out on you unless you did something really stupid or more like it was balanced on a knife-edge where it felt like it could get away from you if you only got a little sloppy?


Norm

[SSLance]

With equal tire traction\grip front to rear, the back feels great. It stepped out a few times on my runs Sunday a little bit, but mainly due to other factors like bumps or too abrupt throttle application at the wrong time. If you are smooth between braking and throttle application the back feels great. Even if it steps out a little bit, it is still very much in control. Depending on the traction at the time you can get it back in line either by giving it a bit more gas transferring weight to the back or letting up just a bit to let the grip catch back up.

When I have unequal traction like with my current street tire setup, the back is way loose but still very controllable. Not knife edgy at all, very controllable with the amount of throttle applied. It is REALLY fun to drive, just not necessarily as fast in the corners as it is with equal grip front to rear.

With my old setup, when running the slicks...coming out of a sharp right hander hard on the gas the car would lift up the right rear tire and overpower the trac-loc and spin just the inside tire. With the new setup, it will still do this under the most extreme circumstances, but it is MUCH better than before. I think it only spun the right rear once or twice coming out of the last righthander before the finish of the course and never enough to really slow the car down...just that it was a bit noticeable.

When I was working the course in heat 3, I noticed a LOT of cars were spinning their tires coming out of that turn hustling towards the finish.

[Tomswheels]

Lance, after this turn, how long was the next straight? I always sacrifice speed in the apex if I can EXIT the turn on the gas sooner (early apex) IF there is a decent straightaway after the turn. Your speed at the end of the next straight will be higher if you get on the throttle earlier, plain and simple. In a Miata, those milliseconds you are NOT on the throttle dont matter much. With your V8 every millisecond off throttle is a wasted opportunity....

[SSLance]

It was a short chute with another 180 to the left at the end, not sure how long 100-150' maybe.

You can see it here on this in car video.

http://youtu.be/jZQiX6p-ELE

[SSLance]

I guess there is also the possibility that I was getting the car through that corner as fast as it was going to go with it's current setup?

That run that I posted the slo-mo video of the front tire locking up was my 2nd try at that corner (and the whole course)...and I ran a 52.438.

The run I showed from inside the car was my 7th try at the course, and I also slid the front tires in that same turn...and ran my fastest time of the day at 49.553.

With that long course with 3 very fast straight sections, there were lots of places to make up time and also to loose time. On my 8th run I over drove the entry to the left hander at the end of the third straight, wheel hopped the car and had to dirttrack the whole corner...and I lost a half second. The rest of the run was clean and very fast.

I guess I should just accept what I ran, learn from my mistakes, and try to keep getting better on my next runs. I'm not sure of a way to tell which is faster on each individual corner in a course with usually only 4 attempts at it during an event. I know this though, every time I lose the back on entry, I lose a LOT of time, but my 7th run shows that I can slide the inside front a bit and as long as it catches without upsetting the rest of the car, I can still put down a pretty good time. My times also show that I can carry less speed through the corners and not slide the fronts, but my times represent that as well.

[Ron Sutton]

Hi Lance,

It is cool to see how much progress you have made with your car at the track. I remember when you posted this in April ...


Car drove a LOT better today, part I'm certain was due to straightening everything with rear suspension out..the rest was the tires. I usually finish about 60-70th out of 100 cars or so in raw time...38th out of 97 cars today!!



Now, with a little work & very little budget, you have improved your car from a pushing mess ... rear tires bouncing ... to a flatter running, neutral handling, smoother "AutoX racer" that is faster, fun to drive & impressing people at the track.


Well, yesterday's event was a whole different story with the new setup.

Here were my times for the day:

Heat 1
#1 53.123 (hit a cone on the inside of first sweeper, was surprised how well it turned)
#2 52.438
#3 52.307
#4 50.260 (last one that was going to count, so I stepped it up)

Heat 2
#1 50.232
#2 49.820
#3 49.553
#4 50.123 (over drove the corner after the last straight, wheel hopped under braking and dirttracked the corner)

Here are the posted raw time results

http://www.kcrscca.org/results/solo/2013/2013_event11_raw.htm

Officially I finished 25th out of 100 drivers. Had my 49.553 counted I would have finished 18th.

Check out the list of cars I finished ahead of! A LOT of those cars are considered "autocross" type cars and a bunch of them were running on some sort of racing compound tire as well. This was done with my 3700 pound 1985 Sport Luxury Monte Carlo with a full interior including AC! Nothing better in my book than beating them at their own game.

I'll let Ron talk about the changes we've made and how they've affected the car from his perspective...I LOVE them and think it can only get better. It's unbelievable the grip this car has now, even with the problems it still has which we will continue to correct upon.


Not sure that it makes any difference but I was up into the mid 60 mph range at the end of all 3 straight stretches on that course. It was really giving the low horsepower cars fits...most of them were shifting 6 times or more during a run.

You should have seen the grin on my face get bigger and bigger as I walked the course for the first time...and then after each run.

Let's recap what you did for anyone following along:

Mapped the roll center & corrected a RC migration problem
Raised car 1" to increase front travel with spring adjusters
Installed larger front sway bar ... kept same 575# springs
Installed stiffer rear springs from 125# to 225# ... kept same rear sway bar
Installed DSE LCA's to add caster
Modified LCA holes to get a little more caster
Increased caster from 5.5° to 7.5° (Better but still about 1.0° -1.5° less than optimum)


Now ... with the higher travel front end & bigger sway bar ... the car is working the front tires much better. The caster is helping keep the contact patch much better. This is one of the keys to taking the bad push out of the car that you had ... and why the corner speeds are up. You can not make a car go faster the front tires have grip. The videos show you still need that extra 1.0° -1.5° of caster. Winter project maybe ?

The stiffer rear springs are keeping the rear tires planted better ... no hop ... plus helping to keep the rear roll angle in line with what the front is doing ... while helping to keep the inside front tire planted better. As you know, I worked out the spring & sway bar combo for the correct FLLD & RLLD. Anyone following along ... the calcs showed the rear spring rate needed to be 207#. I asked Lance if wanted to err on the tight/pushy side or the free/loose side ... and he choose the free/loose side ... which is why we went with 225# rear springs.

Lance, if after you dial in the new shocks ... you find the car is still a bit on the free side ... you can always go to 200# rears to tighten it up. You may find in the early Spring & Fall when the weather is cooler ... and the track has less grip ... the 200# rear springs may be the hot ticket. Then put the 225#s back in for warmer weather.

The one LCA hole that was off ... causing the RC to migrate to the side made the car handle much differently left & right. Correcting that made the car handle more consistently & predictably. One cool thing is you learned how all that stuff worked .. and learned that you can correct & affect your geometry.

What's next:
Replace those 5 year old Edelbrock street shocks with adjustable Ridetech shocks with special valving. I worked with Britt & Herb at Ridetech to develop some AutoX valving. They utilize digressive valving on the rebound side of the front shocks ... with much stiffer low speed rebound valving to better hold the front end down through the roll through zone of the corner ... then release and extend as normal on corner exit. After you get them on your hot rod ... test & tune is next ... then another AutoX event.

It has been a lot of fun working with you ... and it has been very rewarding to see your car's handling & track performance improve so much. Of course there can always be more. That just depends on how hardcore you get in search of performance. :)

[Ron Sutton]

I doubt you've got enough aero effects to where front ride height is sensitive enough to matter at maybe 40 mph, so I think that trying to tie the front down with shock damping might be counterproductive (more rebound damping will lift more load off the inside tire faster during that upward motion than the upward position suggests). More rebound in the rear shocks might be something to try if the car is understeering when you are not sliding a tire like that.

What I think was happening is that you carried a little too much braking a little too deeply into the turn. Eventually the combination of braking traction plus lateral acceleration and the accompanying roll and upward force from shock rebound was more than that tire could handle. So it locked at least partially and made the front slide. The smoke begins to be visible just before 0:14.

Norm

Hi Norm!

I think you'll find it interesting what the car does with stiffer low speed rebound valving in the front shocks. That is a key element to high travel/low roll suspension setups. Lance's car is not a "full" high travel/low roll set-up. It's more of a "Tweener set-up" ... but the same tools apply.

We'll get to see the results in a few weeks when he runs with the new shocks.

Take care !

[SSLance]

Now ... with the higher travel front end & bigger sway bar ... the car is working the front tires much better. The caster is helping keep the contact patch much better. This is one of the keys to taking the bad push out of the car that you had ... and why the corner speeds are up. You can not make a car go faster the front tires have grip. The videos show you still need that extra 1.0° -1.5° of caster. Winter project maybe ?



Thanks Ron, The amount of knowledge I've learned over the summer with your help has been invaluable. Thank you for being patient with me, talking me back away from the ledge at times and getting the whip out on me when I needed it as well.

I have several projects planned for the winter, adding longer UCA bolts to get the additional caster is on the list...along with replacing the body mounts to stiffen the car up and correct some other issues.





One cool thing is you learned how all that stuff worked .. and learned that you can correct & affect your geometry.



You have created more of a monster than you probably know. :naughty::seizure::cheers:






What's next:
Replace those 5 year old Edelbrock street shocks with adjustable Ridetech shocks with special valving. I worked with Britt & Herb at Ridetech to develop some AutoX valving. They utilize digressive valving on the rebound side of the front shocks ... with much stiffer low speed rebound valving to better hold the front end down through the roll through zone of the corner ... then release and extend as normal on corner exit. After you get them on your hot rod ... test & tune is next ... then another AutoX event.

It has been a lot of fun working with you ... and it has been very rewarding to see your car's handling & track performance improve so much. Of course there can always be more. That just depends on how hardcore you get in search of performance. :)





Can't wait to get to working on getting the Ridetech shocks installed. It's gonna take a little bit of work on my part while you sit back, drink beer and watch... :smoke:

Then you are going to have to walk me through tuning them, which I am sure you are up for.

Hopefully that all goes as smooth as the rest of this has and the BMWs, Minis, and Miatas will really have something to look out for at next year's autocross events.

[SSLance]

Well my next project is under way...so I figure I'll start with the nuts and bolts of it here.

An upgrade in shocks was the obvious next choice, as I was competing on 5 year old Edlebrock IAS shocks at all four corners. I guess I left this til last as it is a pretty difficult yet pretty important choice to make in order to get the most out of your suspension.

Ron Sutton worked with the guys at Ridetech and they came up with a shock that they felt would work the best on my car. With my DSE front arms on the car, here were the measurements I made to determine which shock to use.

Fully extended length 12"
Fully compressed length 8.75"
Ride height length 10.375"

That was about a 3.25" stroke. Ridetech had a 2.9" stroke shock body and a 3.6" stroke shock body to chose from. Ron wanted the travel, so we chose the 3.6" body (Comp: 9.73” Ext: 13.33”) and said we'll just figure out a way to get them mounted to the car so they'd travel.

The rear shocks were easier:

Fully extended length 22" (the Edelbrock shocks on it now only extend to 20" and haven't been a problem)
Fully compressed length 13.5"
Ride height length 15.5"

That's a 8.5" stroke, The shocks for the rear are a 6.9” stroke shock with the following dims:

Comp: 13.125”
Ext: 20.025”

Those should fit fine on the car.

Ridetech sent me a mockup front shock body to try to figure out how to modify my brand new DSE arms to drop the shock mount an inch below their shock mount. Once my last autocross event was in the books I pulled the old shock and set out to try to figure it out.

Here's what I was looking at...

https://static1.pt-content.com/images/pt/2013/10/IMG_20131006_100749_538-1.jpg

https://static1.pt-content.com/images/pt/2013/10/IMG_20131006_100023_707-1.jpg

There was going to have to be significant trimming to get the shock body through the bottom of the arm and we were planning on building brackets to bolt onto the old shock mount holes, drop down and mount the new Ridetech shock to.

The more and more I looked at this, the more I didn't like it. Especially if we eventually went to a coil over spring where 100% of the weight would have been on that mount. The most obvious choice was to use Ridetech's Lower Control Arm in place of the DSE arm. A few checks were made to make sure there weren't any significant design differences between the two that would mess up everything else we had worked on so far and that was a non-issue, so front LCAs were put on the list.

For the rears, Ridetech ships an adapter to convert the Trunion style upper mount to a double shear mount as well as an adapter to do a sideways double shear mount on the bottom side. Looks like this.


https://static1.pt-content.com/images/pt/2013/10/DSC03754JPG-1.jpg


Knowing in advance that the shock\lower control arm mount on my QP 9" axle housing is much different than stock, I knew this would take some work. It does... The top mount will work fine or I can convert it to a Trunion style mount that Ridetech also sent. The bottom mount won't work at all

https://static1.pt-content.com/images/pt/2013/10/DSC03758JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03759JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03760JPG-1.jpg

I bought some 3/16s plate steel today, cut it up into some pieces based off of the cardboard templates I made up last night and tonight I will attempt to recreate Ridetech's bottom shock mount, only built to fit my rear axle housing. I made them a bit long to add in some adjustability just in case.

And that's where we stand now. I've got one side of the front off and tonight I'll mock the Ridetech LCA in place with just the shock and measure travel to make sure everything moves freely and plays nice together. I'll also at least get one of the rear bottom shock mounts tacked up and if I'm feeling froggy, may even weld it up on my own instead of farming that part out. We'll just have to see how it goes.

[SSLance]

Things are progressing nicely in the shop with the Ridetech install. Here are some pictures of my "Made by Lance" Lower shock mount brackets for my Quick Performance 9" rear axle housing.

These were taken with the shocks at full compression, no springs installed yet.

https://static1.pt-content.com/images/pt/2013/10/DSC03787JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03788JPG-1.jpg

Probably about ride height

https://static1.pt-content.com/images/pt/2013/10/DSC03789JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03790JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03794JPG-1.jpg

With springs on sitting at ride height.

https://static1.pt-content.com/images/pt/2013/10/DSC03796JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03797JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03795JPG-1.jpg

Fully extended with springs

https://static1.pt-content.com/images/pt/2013/10/DSC03800JPG-1.jpg

https://static1.pt-content.com/images/pt/2013/10/DSC03799JPG-1.jpg

The shock travel with the mounts in this manner basically mimic the shock travel I had with my stock style shocks. Full compression is about 13" center to center, ride height is about 15.5" and fully extended is 20". The bump stop on the shock contacts the shock body just before the bump stop on my axle contacts the frame.

For the front install I had to finesse the front control arm mounts on my frame a bit to fit the Ridetech LCAs in place, but that wasn't a big deal once I figured out what to do. I've learned over the years that the frames on these G-Bodys are loosey goosey and if something isn't fitting properly it isn't that difficult to get the frame part moved to make everything line up. I then pressed the Howe Tall lower ball joints out of my DSE arms and pressed them into the Ridetech arms and bolted them in place without issue. The travel of the front shocks is good, with ride height set at 26" at the fender, they will compress down to 23" at the fender before the bump stop on the shock stops the travel. They will extend up to at least 29" at fender as well, I haven't measured exactly how high they'll go before lifting the tire off of the ground.

One other thing I had to do to fit the front shocks in place was open up the shock tower hole on the frame from .600 to .750 so that the mono ball stem on the shock mount would fit through the frame. other than that it was pretty much plug n play just like the rears.

[SSLance]

So with everything shock related mocked up and in place except for the shock reservoirs, this is what I've been working on this week

I've ordered a pair of these

https://static1.pt-content.com/images/noimg.gif

http://www.sealsit.com/grommet_split.asp

And once they get here I'll prepare myself mentally to cut two 3" diameter holes in my trunk floor up near the center of the shelf above the rear axle. The reservoir lines will leave the top of the shock mounts, wrap around the old coil spring spuds on the frame and head to the center where they'll go up through the floor of the trunk and the reservoirs will be mounted pointed back out to the outside of each respective side. Their placement will allow me to open the trunk and reach the adjustment knobs on each reservoir very easily plus give a secure and safe place to mount them out of the way. Hopefully the grommets provide a good clean safe way to seal the holes back up again.

The front shock reservoirs will just be mounted somewhere near the top of the front shocks on the inner fenderwell so all three adjustment knobs up there will be easy to access as well.

I've been working on the alignment settings with the new front lower control arms. I ordered the Joes Racing caster camber gauge and started checking it out Tuesday night. I had to remove my dust caps, the cotter pin and wheel bearing nuts, take the bearing washer out and put the nut back on the spindle to have enough thread to thread the tool onto the spindle. Once there I checked all of the settings.

I knew my steering wheel was centered before so I centered it again and put several pieces of masking tape on the top of my steering column and also on the steering wheel itself then made a mark going across both to give me a reference mark showing when the steering wheel is centered.

To check caster, you have to know when your front wheels are turned 20 degrees left or right. If you notice on the gauge...

https://static1.pt-content.com/images/noimg.gif

On the outside of it there are two edges that are pointed 20 degrees toward the inside. With the gauge on the drivers side front wheel, I turned the steering wheel to the left until the level I put on that end of the gauge was parallel with the body of the car, representing a 20 degree turn to the left. Once I was sure it was parallel, I put a mark on the steering wheel masking tape even with the mark on the column, noting a 20 degree turn to the left. Then I repeated that procedure for the passenger side.

To check Caster, what you do is turn the driver's side wheel 20 degrees to the left, level the bubble on the end of the gauge, then adjust the thumbscrew on the center part of the gauge to set the caster bubble to zero. Then turn the steering wheel all the way to 20 degrees to the right (line up the other mark on the masking tape) and boom...read your caster number on the bubble level. Easy Peasy...

To do the passenger side just reverse the above procedure.

Reading Camber settings is even easier. Level the gauge on the respective spindle and read the bubble on the level.

Now...and this is the part where I can't seem to get it through my thick head how to do this stuff right the first time.

It is CRUCIAL to have the car sitting at ride height, on a square and level floor before starting to read or mess with these adjustments.

When I first put the gauge on a spindle, I was so excited about how easy it was to use, I just started measuring, making notes and then went right into making adjustments pulling out shims, measuring, and repeating all while checking for tie rod clearance at the frame at full compression (my main interference point). I had my two post lift arms set under the frame, 10.5" of wood stacked under the rear tires and my car ramps and two double laminated pieces of plywood under the front tires at 10.5" tall as well. Coilover springs on the rear were set to ride height, driver side front shock was installed with no spring, no passenger side shock was installed. After messing with it quite a bit tweaking the driver side caster and camber getting it just so where I thought it was best, I went to the passenger side and it was all out of whack. :banghead:

I then realized what was going on. My lift arms are not exactly level with one another, so as I was raising and lowering the frame of the car with the lift with no springs in the front, essentially the passenger side of the frame was about a 1/2-3/4" lower than the driver side. This WILL mess your readings up!! Not only that, the weight of the engine forces the front of the frame to flex down 1/2-3/4" when the frame is lifted behind the front tires...also detrimental to getting accurate measurements of front geometry.

So, I punted for the night and came up with a new plan of attack.

Last night I first I installed the passenger side shock (no springs) to match the driver side. I then set the rear tires on the floor sitting on one flat 2x6 raising them 1.5" up off of the floor. I set the front tires on the two pieces of 3/4" laminate plywood on the floor, basically setting all tires 1.5" up off of the floor. I then put my floor jack under the front crossmember and lowered the car off of the lift arms and got them out of the way. I discovered that my jack would not go low enough to drop the front of the car to full compression (necessary for setting bump steer) so I put another 2x6 under all four tires raising them all to 3" off the floor and that gave my jack the clearance it needed. Basically this let me set the rear coilovers to exactly the desired ride height and to use the floor jack to raise or lower the front suspension with the complete weight of the car, engine, frame body etc on the jack\frame just like it would be if there were springs on the shocks.

I then only used the jack to move the front of the car up and down as needed and remeasured all of my current alignment settings on both front wheels. Of course, the adjustments I made the night before completely screwed the Drivers side up due to readings being off because the body of the car was canted to the passenger side and the frame was drooping 1/2-3/4s" under the weight of the engine.

What I also found was with the weight on the frame in this correct state, I could get another 1/2" of compression travel before the bump stops settled and the tie rod hit the frame.

#startover

I then quit for the night knowing that the next time in the shop the car is all jigged up ready to go and all I have to do is start taking readings again, making adjustments and taking readings once again. It should go pretty fast now, it really doesn't take that long to loosen the UCA nuts, slip a few shims in or out tighten back down and check again and I have a pretty good idea now of what needs to be changed to get things where we want them for maximum front tire contact in all scenarios.

Lesson here, car HAS to be in static ride height condition in order for the tools and procedures to work properly...live it, learn it...

And that's where I'm at right now. Hopefully tonight I'll get a real good set of adjustments made to the camber, caster, bump steer and toe and get the front end locked down. Then it'll just be a matter of installing the front springs, mounting the reservoirs, nut and bolting everything and a test drive to start tuning the shocks.

[SSLance]

Alignment is done, as are bump steer adjustments.

Got -0.50 static camber on both sides and +9.25 caster driver, +9.125 caster passenger side. Close enough for now, I'll fine tune that on the alignment rack once I get some longer UCA bolts in the passenger side.

At 2" of fender compression from ride height, the camber gains to -2.50. Toe stays steady until about the same height, then it toes out just a bit as the fender goes to 23" or full compression...exactly as Ron prescribed.

With a fender ride height of 26", the front will compress to 23" where it sits on the shock bump stops. At this point the tie rod is just kissing the frame, it will still move easily for about a half turn of the steering wheel each way before binding up. Lifting the car 1/4" freed it up completely. I still need to extend the stock style sway bar end links a bit to keep the sway bar off the tie rods, I'll measure for that before putting the front springs on, shouldn't be a big deal though. The bolt will be long enough, just need to add some spacers to it.

Fender will rise to 29" without lifting the tire off the ground giving a front wheel travel of at least 6", 3" compression, 3" extension.

I have 700# 8" long springs and 600# 10" springs on hand for the front.

I have 200# and 185# 12" long springs for the back. Ron has calculated the 185# rear & 600# front for the correct Tweener high travel/low roll setup.

I'll have to compress the 600# springs approx. 1/2" to pre-load them on the shocks.

Tonight we start bolting on parts for the final time and nut n bolting everything to make sure it's all tight. Biggest part of this will be cutting the 3" diameter holes in the trunk floor for the reservoirs...

The build continues...

[SSLance]

I'll have to compress the 600# springs approx. 1/2" to pre-load them on the shocks.




So this was interesting, and I wonder if the exercise I went though yesterday is why people to use a shorter shock and a stiffer shorter spring when putting a coil over setup on a G-body or similar frame rather than the 3.6" travel shock and 10" spring.

The good news is though, I figured out a way to make it a pretty easy install.

After trying 3 different spring compressors with no luck in getting the spring on the shock, I took the whole assembly back apart and started from the beginning. I knew I was going to have to use either my press or the weight of the car to compress the spring enough to get the spring on the shock. With the shock's top mount apart and in my hand, it hit me...

I put the lower plastic ball part of the mount into the hole in the frame from the bottom. I then put the lower spring adjuster all the way down on the shock body (mistake, will explain later) then the 10" spring, then the upper spring retainer and the aluminum top mount with the clip in place. The length of the spring made the top mount not go all the way down on the shock, but that was okay.

The lower ball joint was loose, so I slid the shock into place in the A-arm and put the bottom bolt in place, then lifted the A-arm while directing the shock assembly into the hole in the frame. Once it touched, I put my screw jack under the A-Arm and used the jack to lift the A-arm and shock up, compressing the spring at the same time. As it got there, I guided the lower ball joint into the bottom of the spindle and lifted it up until it was tight in place. I inspected the top shock mount and everything was right in place.

At this point I kicked myself in the butt as I just did in 10 minutes what I had spent the last three hours trying to do...unsuccessfully. :banghead:

I put the top two pieces of the shock mount in place on top of the frame and tightened the nut down. Boom...coil over shock installed. I did the same to the other side and lowered the car down to check the ride height. Fender was about an inch lower than we wanted it, that meant the bottom spring adjuster needed to go up about a half inch. While I was doing the passenger side, my brother finished up the install on the drivers side including the sway bar mount and the cotter pin in the ball joint stud. Second mistake...

We tried to raise the adjuster up with the spanner wrench but the adjuster being at the very bottom of the shock down in the dropped A-arm mount, there wasn't room to get the spanner wrench in there much less turn it with pressure on the spring. The smart thing to do would have been to bust the lower ball joint loose again, lower the A-arm taking pressure off the spring, run the adjuster up by hand and re-install. We did it the other way. We used a hammer and a punch to turn the adjuster about 3 turns before we could get a good bite on it with the spanner wrench to run it the rest of the way up we needed. This isn't particularly easy and I strongly suggest to not use this method, but we made it work anyway.

Once both of the adjusters were ran up a half inch we lowered the car down again, jounced the suspension up and down a bit, rolled the car back and forth and measured again...we need another couple turns on each and it was good. We then stopped for the night and today I finished up the install and test drove.

What we've learned here is that it is possible to run a 3.6" travel shock with a 10" 600# spring in the front of a G-body. The pressure it takes to move the front down on the springs feels very similar to the 575# conventional springs I had in it before and it drives very similar as well.

I haven't started adjusting on the shocks yet. I set all three settings at -12 clicks on all 4 shocks for the initial test drive. The rear feels a little bit more stiff than before but the front feels VERY similar to the old setup. Travel, turn in, weight transfer, control, ride, all are very nice as is...but I'm certain I can make them all much better with some tuning, which is next. I need to clean up the shop and spend some time with my wife for a day or so first...then get back after it.

Hopefully this will show though that you can make a long travel coil over setup work on a G-body without resorting to putting a super stiff spring in due to space constraints or install difficulties. It really isn't that hard to do now that you know how.

[instro84]

Nice work Lance, i'm going with ridetechs on my buick also just the single adjustables thou. Hope to order bynthe end of the week.are you gonna use those camaro brakes or stay with stockers?

[Norm Peterson]

It's not surprising that 600# coilovers feel similar to 575 # big springs, since the big springs are roughly concentric to the shock and would have at least a similar motion ratio.

One of the things to do next would be to cornerweight the car. Getting the ride heights equal does not guarantee that the corner weights are balanced. You'll probably want at least one endlink on the front sta-bar to be adjustable so that re-connecting the bar won't upset the corner weights after you've gone to the trouble of getting them set.


Norm

[Ron Sutton]

It's not surprising that 600# coilovers feel similar to 575 # big springs, since the big springs are roughly concentric to the shock and would have at least a similar motion ratio.

One of the things to do next would be to cornerweight the car. Getting the ride heights equal does not guarantee that the corner weights are balanced. You'll probably want at least one endlink on the front sta-bar to be adjustable so that re-connecting the bar won't upset the corner weights after you've gone to the trouble of getting them set.

Norm


Both great tips.

Lance you told me you know of a race shop where you can scale it. That will be key. Can you do it before next week's event?

P.S. Norm, the Ridetech LCA's move the lower mounting point of the shock out, which, even though it increases the shock angle, did increase the motion ratio a small bit. In the rear, changing from inboard mounted coils to outboard mounted coil overs increased the side-to-side motion ratio a lot, so we needed to go down in spring rate, to keep the same wheel rate.

[SSLance]

Unfortunately I doubt it... I'm struggling just trying to figure out the best way to get the shocks tuned by then for now. Between the shorter fall days, my other commitments, my lack of tire availability (street and\or slicks) and just my flat out lack of time...I'm pessimistic about getting the shocks completely tuned in by Sunday's event.

Hopefully things will work out, otherwise I may be tuning them at the event...which isn't the preferable method under any circumstances...but it is what it is.

I had to buy longer bolts (8" vs 7.5") for my sway bar end links and space the bushings out by about 5/8s" longer than stock with washers to keep the tie rods off the sway bar at full compression. Even then I had to snug the bushing down without the top washer, then pull the nuts, put the washer on then put the nut back on quickly so there was enough thread showing to get the nut on. To put any more adjustment on the sway bar links I'll need even longer bolts or rig up a more suitable adjustable style end link which would probably be the best solution.

[AutoX_a_Truck?]

Unfortunately I doubt it... I'm struggling just trying to figure out the best way to get the shocks tuned by then for now. Between the shorter fall days, my other commitments, my lack of tire availability (street and\or slicks) and just my flat out lack of time...I'm pessimistic about getting the shocks completely tuned in by Sunday's event.

Hopefully things will work out, otherwise I may be tuning them at the event...which isn't the preferable method under any circumstances...but it is what it is.

I had a similar problem when I was trying to dial in my shocks. It's tough get even a good ballpark/baseline tune without a good course to test on. At events it can be tricky too with only 3-5 runs in quick succession (more so with multiple drivers). I went to a KCRSCCA test and tune once and it was great for dialing in my shocks, tire pressures, and sway bars. But, unfortunately, those are usually only at the start of the season.

[SSLance]

I'm contemplating signing up for double duty again this event just so I'll have 8 runs instead of the usual 4. Sure makes for a long day though.

Saw that you signed up Tyler, should be a fun course to run on for us. Have you seen the course map they released last week yet?

[AutoX_a_Truck?]

I'm contemplating signing up for double duty again this event just so I'll have 8 runs instead of the usual 4. Sure makes for a long day though.

Saw that you signed up Tyler, should be a fun course to run on for us. Have you seen the course map they released last week yet?

I am excited to squeeze in one more event before the season ends. My Dad is going to drive the Scout II (couldn't resist the pun) so I will have some friendly competition. The course looks fun! I just hope it won't be too cold. I will be trying out a new gear set in the T5 with different ratios so I hope that works out.

[Norm Peterson]

P.S. Norm, the Ridetech LCA's move the lower mounting point of the shock out, which, even though it increases the shock angle, did increase the motion ratio a small bit. In the rear, changing from inboard mounted coils to outboard mounted coil overs increased the side-to-side motion ratio a lot, so we needed to go down in spring rate, to keep the same wheel rate.


Got it.

That would also be in the direction of a higher travel/lower roll setup, right?


Norm

[Ron Sutton]

Got it.

That would also be in the direction of a higher travel/lower roll setup, right?

Norm

Yes. Lance is on a "Tweener set-up" ... in-between a conventional set-up & a high travel set-up. He's traveling the outside wheel about 3", so not high travel like 4"-5.5" we normally do, but more than conventional set-ups that are typically around 1.5"-2".

[UMI Tech]

I've been following this thread and have learned a ton. Based on what I've seen it led me to contact Ron Sutton awhile back for G-body setup help. Our local oval track reopened as an asphalt track after years as a dirt track (they brought clay in 10 years ago and ruined it). Ron helped me convert a local dirt track G-body to a pavement car for an open event. This thing was bad fast right off the trailer and that NEVER happens with a new setup. It's pretty cool how many of the oval track things and auto-x things cross over. Keep up the good work Ron and thanks for the teaching.

ramey

[SSLance]

It's pretty cool how many of the oval track things and auto-x things cross over. Keep up the good work Ron and thanks for the teaching.



My favorite part of what we've done with my car so far is that none of it has hurt it's street driveability at all, so you could say that it crosses over from Auto-x to the street as well.

Take care of the bump steer properly while making the changes and the changes will actually improve the street driveability while making you faster at the track at the same time.

[UMI Tech]

I agree on the bump steer. Some years ago I had a mid-year Monte Carlo in the same division. I spent countless hours tuning the bump steer, massaging parts and so on until it was perfect. The first laps were very uneventful. I pulled in rather irritated that it felt slower. Yeah, slower to the tune of minus three tenths (which is huge). Best improvement I've ever made.

ramey

[83hurstguy]

Nice job with your install!

What's the motion ratio difference between the stock G-body LCA and the Ridetech LCA? I'm curious what the wheel rate difference turns out to be with 550 lb/in springs in the stock arm vs the 600 lb/in in the Ridetech arm. I was turned off on G-body coilovers by the high spring rates required due to limited travel, but this is encouraging.

[SSLance]

Thanks... I see you are from Kansas City, glad to see another local on here. I don't know how to figure the exact motion ratio difference out, maybe Ron does. I believe he has all of the exact measurements of the different arms and mounting locations. I have them too if you want to figure out the differences between the arms.

You should come out to our autocross in Independence this Sunday to watch us run. It's our last event of the year and there are a lot of fun cars signed up already, along with a fun course design.

[Norm Peterson]

For most front suspensions, there are at least three components of motion ratio. For comparing spring rate to wheel rate, their numbers all get squared and the overall motion ratio is the product of the three component terms 'squared'.

1. Ratio of the length from chassis pivot axis to spring (and/or shock) to the length from the pivot axis to the ball joint
2. Spring and/or shock angle (either the sine or cosine depending on whether you're measuring these angles from the vertical or from the horizontal, respectively)
3. Ratio of the length from the Front View Instant Center to the ball joint to the length from the FVIC to the center of the contact patch

The first two components give you a "ball joint rate", which is not necessarily the same as the true wheel rate even though it's fairly close most times. That last one is what gets you from the ball joint rate to the wheel rate and is generally a small effect. However, it does become more important with larger values for scrub radius (the contact patch force centroid is further away from the ball joint). It's something to perhaps keep in mind for use as a "tie-breaker" if you're on the fence between which of two spring rates to go with.

Keep in mind that any bushing compliance makes this entire line of math an approximation rather than an exact solution. For big springs, even the effective spring location on the control arm is somewhat vague.


Norm

[Ron Sutton]

Hey Lance,

Repost all the LCA dimensions so I don't have to look for them. I need the coil over inward angle too.

[SSLance]

Stock LCA
Center Pivot to Lower Ball Joint 14 7/8"
Center Pivot to Spring Center 6 3/4"
Center Pivot to Shock Center 7 3/8"


DSE LCA
Center Pivot to Lower Ball Joint 14 1/2"
Center Pivot to Spring Center 6 7/8"
Center Pivot to Shock Center 7 3/8"



Ridetech LCA
Center Pivot to Lower Ball Joint 14 5/8"
Center Pivot to Spring Center 8 1/2"
Center Pivot to Shock Center 8 1/2"

[83hurstguy]

Thanks guys.

Lance, I'll have to try to make it out. Let me know where you are going to be in Independence with time frames, I'm down in Overland Park. My car was almost ready to go out, been down all summer, but a brand new rear axle seal decided to start seeping last weekend, so it's blown back apart. Definitely interested in seeing your car run in person.

Norm, appreciate the details, I assumed that we are dealing a series of assumptions to get a "best estimate", due to measurement accuracy, the odd G-body angles of a separated spring/shock that aren't necessarily collinear.

[SSLance]

Kansas City Region SCCA autocrosses here most of the time

http://www.kcrscca.org/new/content/mcc-blue-river-precision-drivng-center

MCC - Blue River Precision Driving Center

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Directions to site - I-70 to Highway 291 - take 291 north
about 2 miles to Highway 78 (also called 23rd street). Turn right on
Highway 78 and go east for about 2 miles to the Metropolitan Community
College - proceed past the College east on Highway 78 about another 1/2
mile. At the bottom of the hill, there is a road to the right (South)
that leads to their Precision Driving Center.


Admission is free, you can come or go as you like just have to sign a waiver and get a wristband when you first go in. There is a little bit of restrictions about who can be in the "hot pits" during runs but other than that, you can see or do it all while there. There will be 100+ cars out there for the Oct 27th event. I'm signed up to run in Heat 2 which will be on the track probably 11:00-1:00 or so.

If you are planning on coming out or if you have any questions about this, just let me know.

Lance

[SSLance]

I've ordered a pair of these

https://static1.pt-content.com/images/noimg.gif

http://www.sealsit.com/grommet_split.asp

And once they get here I'll prepare myself mentally to cut two 3" diameter holes in my trunk floor up near the center of the shelf above the rear axle.

I just wanted to update this to say these particular seals did not work for me. It takes every bit of a 3" diameter hole to get the reservoir through, which is what I cut with a 3" hole saw.

These seals are 3" in diameter to the outside edge of the metal part of the seal, probably only good for a hole about 2 5/8s" in diameter. Seals-it makes a larger split grommet seal that seals up a 3 3/4" hole but they are $44.95 each, so I passed for now and returned the 3" seals.

They are nice seals and if they'll fit your application, go for it...they just wouldn't work in my situation.

I'm still working on an alternative plan to seal up the holes in my trunk floor.

[83hurstguy]

I'll send you a PM in a bit so your suspension thread stays on topic. Thanks for the details!

[Ron Sutton]

Lance, here is your shock tuning game plan & guidelines for tuning with Triple Adjustable Ridetech Shocks

Before you get into full bore tuning ...
A. Do you have a safe place to test? (Meaning safe for you AND others)
B. Start with all the shocks FULL STIFF on all 3 settings.
C. Adjust all 3 settings on each shock to the middle, which is minus (-) 12 clicks.
D. There is no need to adjust the high-speed compression any further for tuning.
E. Track test with "just" shock adjustments & nothing else.
F. Take detailed notes of every change, before every "run".
G. Make 4 click increments in the first round of “rough tuning.”
H. Use 1-2 click increments for “fine tuning” sessions.

Make these tuning changes in this order:
1. Soften the low-speed compression on the fronts … until you get the car "loose on entry" when braking & turning & back up ... or go until you run out of adjustment.
2. Stiffen the low-speed rebound on the rears. You will gain grip back on entry. Go until the car gets loose again on corner entry turning & back up ... or go until you run out of adjustment.
Step #2 will also provide more grip on corner exit. Pay attention to when it affects grip on entry & middle.

3. Stiffen the low-speed rebound on the fronts to help keep the nose pinned down in the roll through zone. Go until the car gets loose on corner exit & back up ... or go until you run out of adjustment.
4. Stiffen the low-speed compression on the rear shocks until the car gets loose anywhere & back up ... or go until you run out of adjustment.
Steps #3 & #4 will help the car turn better "mid-corner" when you're "rolling or coasting" with no brakes or throttle.

The middle of the corner is the highest priority. If the car won’t turn well in the middle, the entry & exit are inconsequential.

Please do these in this order & take lots of notes. You won't be able to remember all the details accurately. I don't know any top race teams that don't use "run sheets" to keep track of changes, results, etc.

Then, send me a report of each run, with all 4 shock settings, the handling results on corner entry (braking & turning), Middle (coast) & Exit (throttle roll on & steering unwind) ... and the differences from the previous run.

You'll learn first hand what changes do ... I'll guide you on what everything means to us from what you send.

-------------------------------------------------------------------

Then, go back through the same process, but fine tune with 2 clicks, then again in 1 click increments until you find the best balance.
• Experiment with a “little here & a little there” strategy.
• Experiment with a “less here & more there” strategy.

Once you’re “happy” with the handling … this is your baseline set-up. Write it down & place it in a vault. Whenever you find yourself “out-to-lunch” with tuning … go back to your baseline.

If after more events & testing, you improve on your shock settings, make that your new baseline. Write it down & place it in a vault. Whenever you find yourself “out-to-lunch” with tuning … go back to your baseline.

-------------------------------------------------------------------

 
Fine tuning for day, track, conditions, etc.

Loose Entry:
• Stiffen the low-speed rebound on the rears. You “may” gain grip back on entry. If it gets better, go until the car gets loose again on corner entry turning & back up ... or until you run out of adjustment. If it gets worse … stop & back up to the baseline setting … and move on to the next step.
• If still loose, stiffen low-speed compression on front shocks until the car grips up on entry. Don’t go any stiffer than needed, as this may tighten up the roll through zone.
• If still loose on entry, reduce rear braking force with adjustable proportioning valve.
• If still loose on entry, try braking softer & longer.
• If still loose on entry, the cure will require a stiffer front spring or sway bar rate.

Tight/Pushy Entry:
• Soften low-speed compression on front shocks until the car frees up on entry. Don’t go any softer than needed, as this will make the car loose on entry.
• If still tight/pushy … soften the low-speed rebound on the rears. Go until the car gets loose again on corner entry turning & back up ... or until you run out of adjustment.
• If still tight/pushy … stiffen the low-speed compression on the rears. Go until the car gets loose again on corner entry turning & back up ... or until you run out of adjustment.
• If still tight/pushy on entry, induce rear braking force with adjustable proportioning valve.
• If still tight/pushy on entry, try braking harder.
• If still tight/pushy on entry, the cure will require a softer front spring rate.

Loose during “roll through zone” only:
• Pinch yourself, because you’re dreaming.
• Are you sure the car isn’t loose, or pushing, on entry causing the car to get loose in roll through zone only?
• This is great news … brake softer, but the same length & increase the roll through zone speed until the car comes back to neutral handling. If it get’s tight, you may need to brake slightly harder to decrease roll through zone speed & cure it.
• Ok, if it is really loose in roll through zone only … soften up the low-speed rebound valving on the front shocks.

Tight/Pushy during “roll through zone” only:
• Stiffen low-speed rebound on the front shocks until the car frees up in the roll through zone.
• If still tight/pushy in the roll through zone, stiffen the rebound on the front shocks until the car frees up in the roll through zone.
• If still tight/pushy in the roll through zone, soften the low-speed rebound on the rear shocks until the car frees up in the roll through zone.
• If still tight/pushy during “roll through zone” only, brake harder, but the same length & decrease the roll through zone speed until the car comes back to neutral handling.
• If still tight/pushy in the roll through zone, the cure will require more than shock & braking adjustment.

Loose Exit:
• Stiffen the low-speed rebound on the rears. Go until the car gets tight on exit … or loose on corner entry …and back up ... or go until you run out of adjustment.
• If still loose, soften low-speed rebound on front shocks until the car grips up on entry … or gets tight in the roll through zone. Don’t go any softer than needed, as this will tighten up the roll through zone.
• Do not soften the low-speed rebound on the front shocks UNLESS the roll through zone is awesome AND the tires spin the instant you touch the throttle.
• If still loose on exit, experiment rolling the throttle on later or slower.
• If still loose on exit, the cure will require more than a shock or driving adjustment.

Tight/Pushy Exit:
• If any adjustment range left, stiffen the low-speed rebound valving on the front shocks. Go until the car gets good on exit ... or go until you run out of adjustment.
• If still tight/pushy on exit, soften the low-speed rebound on the rears. Go until the car gets good on exit ... or until it hurts the entry … or until you run out of adjustment.
• If still tight/pushy on exit, experiment rolling the throttle on later or slower.
• If still tight/pushy on exit, the cure will require more than a shock or driving adjustment.


Keeping Accurate Tuning Notes:Here is the common way in racing ...

a. Everything is from full stiff.
• - means softer
• + means stiffer
• HSC is High Speed Compression
• LSC is Low Speed Compression
• LSR is Low Speed Rebound

b. After the first setting, we always write the change clicks AND the total clicks

c. If you start by softening all three settings by 12 clicks, we write it like this

LF:
HSC -12
LSC -12
LSR -12

RF:
HSC -12
LSC -12
LSR -12

LR:
HSC -12
LSC -12
LSR -12

RR:
HSC -12
LSC -12
LSR -12

---------------------------------------------------------------------------

d. Then from there ... if you stiffened the low speed rebound 4 clicks only on the front shocks, we write it like this:

LF: LSR +4/-8

RF: LSR +4/-8

That means we stiffened the low speed rebound 4 clicks ... and ended up at 8 clicks from full stiff.

---------------------------------------------------------------------------

e. If you softened the low speed compression by 4 clicks only on the front shocks, we write it like this:

LF: LSC -4/-16

RF: LSC -4/-16

That means we softened the low speed rebound 4 clicks ... and ended up at 16 clicks from full stiff.

--------------------------------------------------------------------------------

This way, at any point, you know what the total is.

Make sense?

[SSLance]

Makes perfect sense Ron, thanks!

I'll make out a worksheet to take copies of with me when I go out and test to make it easier to record notes onto. Along with a copy of the instructions...

When you break the shock tuning procedure down like you have above in the instructions, it paints a much clearer picture of what we are trying to achieve with adjustable shocks and how they work as the brains of the suspension. I can't wait to start tuning on them to watch and feel how they react and how the car reacts once they are dialed in.

I'll keep you posted with the updates.

[83hurstguy]

Lance, thanks again for the ride today! You and Ron have got this thing smokin! Hope you got a good clean run after we had to take off.

Car is handling absolutely awesome. Definitely the best handling G-body I've ridden in. Now I have to get my can in gear to get mine out there next year.

[SSLance]

No problem Luke, was nice meeting you and your wife. Sorry about the "incident" during your ride along. :drive1:

I'm working on gathering up all of my notes, pics and videos of the weekend past and will update the thread once it's all organized, digested, and fit for public consumption. Was a blast though, huge turnout... 124 drivers competed in our event yesterday.

[SSLance]

Saturday morning I headed out to do some parking lot testing and tuning of the Ridetech triple adjustable shocks to try to establish a baseline setting to start out Sunday’s event with. I was armed with Ron Sutton’s shock adjusting checklist, a notebook with some worksheets I made up to help me record notes, and my GoPro.

I had scoped out a church parking lot about 5 miles from my house that looked like a great place to make some runs. Being wide open with nobody around and asphalt in pretty good shape were key. I didn’t want to put too much wear or heat into my race slicks as I needed them at their best for Sunday, so I had my street tires on.

Ron had me set all of the shock settings at -12 clicks for an initial setting except for the rear high speed compression which we set at full soft -24 clicks. Ron had spec’d 175# springs for the rear but all we had were 185# springs so we compensated by setting the rear high speed compression at full soft. I made several figure 8s in the parking lot in second gear, accelerating up to about 40 mph, braking hard then turning in, rolling mid turn, and accelerating off the corner back to the other end of the lot to repeat.

Right away it was stopping and turning in pretty well but the rear was loose middle to off.

Low Speed Rebound -12 Front -12 Rear
Low Speed Compression Little Knob -12 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: 50 degrees, street tires, 3/4 tank fuel, 50 degrees, street tires, 3/4 tank fuel

Using Ron’s how to guide, I softened the Front Low Speed Compression knob 4 clicks and ran again

Low Speed Rebound -12 Front -12 Rear
Low Speed Compression Little Knob -4/-16 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes Turned better on entry and middle (As the adjustment intended) Still loose middle to exit

4 more clicks softer on the Front LSC knob and more runs

Low Speed Rebound -12 Front -12 Rear
Low Speed Compression Little Knob -4/-20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Wheel hopping rears on brakes, Still loose on exit

Ron had told me to go until it gets loose beforehand. When we talked after this session, he informed me wheel hop is the early stages of loose, and in the future to stop there & back up.

Then 4 more click softer on the Front LSC knob and more runs

Low Speed Rebound -12 Front -12 Rear
Low Speed Compression Little Knob -4/-24 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Loose on entry

There it is, just as Ron said. Simple "loose" comes after the wheel hop stage. After these adjustments it had gone from wheel hopping the rears under braking to flat out loose on entry. I was beginning to see just how moving one knob a few clicks on the shock adjuster was really starting to change how the car handled.

I backed up the LSC on the fronts 4 clicks and added 4 clicks stiffening the Low Speed Rebound on the rears. This brought back rear grip on entry.

Low Speed Rebound -12 Front +4/-8 Rear
Low Speed Compression Little Knob +4/-20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Sticks on entry

If a little is good, let’s try some more…4 more clicks stiffer on the LSR rear.

Low Speed Rebound -12 Front +4/-4 Rear
Low Speed Compression Little Knob -20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Slid fronts mid corner, Wheel hopped on entry (Again, had I known beforehand, I would have stopped here & gone the other direction.)

I didn't really realize it at the time, but as Ron explained to me in between sessions that the rear tires wheel hopping under braking is a sign of loose in the rear. Made sense to me what had been happening then.

I went one step further stiffening the LSR rear 4 more clicks and was loose on entry, pushed bad mid corner, and way loose off.

Low Speed Rebound -12 Front +4/-0 Rear
Low Speed Compression Little Knob -20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Loose on entry, pushed bad, loose off

So I backed up that last change 4 clicks softer LSR rear, and added 4 clicks stiffer Low Speed Rebound on the fronts. This was all starting to make sense to me at this point. Feeling how the changes to the shocks were changing the way the car handled was really eye opening. The front got MUCH better, still a little loose in and off.

Low Speed Rebound +4/-8 Front -4/-4 Rear
Low Speed Compression Little Knob -20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes:Turns much better mid corner, Little wheel hop rear enter, Little loose exit

Put in 4 more clicks LSR front, braked a little lighter so it didn't wheel hop in, turned good, but loose off, I made the note WAY loose off…

Low Speed Rebound +4/-4 Front -4 Rear
Low Speed Compression Little Knob -20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Less brake, no wheel hop, turns good, Loose off--WAY loose off

Backed that last adjustment up and ran again. Gained grip on exit and could make both ends stick pretty good with slight driving adjustments.

Low Speed Rebound -4/-8 Front -4 Rear
Low Speed Compression Little Knob -20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Gained grip on exit, can make both ends stick with driving adjustments

Then on to the Low Speed Compression Rear, +4 clicks. Braking was good, turn in good, loose on exit.

Low Speed Rebound -8 Front -4 Rear
Low Speed Compression Little Knob -20 Front +4/-8 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Loose on Exit

Back that adjustment back up, ran again.

Low Speed Rebound -8 Front -4 Rear
Low Speed Compression Little Knob -20 Front -4/-12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Entry-mid turn great, Early exit okay, late exit loose

At this point I was done with the first part of the checklist, so I headed home to confer with Ron. After taking pictures of my notes and sending them to Ron, we talked about all of the adjustments I made so far. We talked about how the adjustments softening the Low Speed Compression on the fronts early on was making it loose and causing the rear wheel hopping under braking. We decided somewhere between -16 and -20 clicks there would be the ticket.

We then talked about the Low Speed Rebound on the rears was affecting the rear and decided that somewhere between -8 clicks and -4 clicks would be the ticket there. We also talked about the Low Speed Compression Rear which he stressed that we’d only use to fine tune middle of turn handling.

I then bolted my Hoosier A6 race slicks on the car and headed back out for the second part of the tuning. I went to a school parking lot pretty close to the house and found a decent spot that was concrete on one end and asphalt on the other. This intrigued me because where we autocross is a mixture of asphalt and concrete.

I made my first run with the shocks adjusted to where I left off before. It was pretty balanced but a bit loose on exit.

Low Speed Rebound -8 Front -4 Rear
Low Speed Compression Little Knob -20 Front -12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes Slicks added, different parking lot, Entry good grip, Middle a tick free, Exit loose a little

I went 2 clicks stiffer Low Speed Compression front, 2 clicks softer Low Speed Rebound Rear and 2 clicks stiffer Low Speed Compression rear. You can see my note I made below. It was like a light bulb went off in my head, it just worked.

Low Speed Rebound -8 Front -2/-6 Rear
Low Speed Compression Little Knob +2/-18 Front +2/-10 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Holey Crap-Nice! Entry good grip, Middle good grip, Exit good grip

I got my camera out and made a run each with the camera on all 4 tires of the car.

http://youtu.be/8Xm2Lv4KD_Y

You can tell watching the video how once the front is set in dive, it stays down through the corner without coming back up until exit. I still don’t know much about exactly how shocks work, but Ron says this is what the valving he had Ridetech put into these shocks does. All I know is, this car turns…and turns VERY well which was it’s Achilles’ heel before. I can’t tell you how much confidence it gives you diving into a corner know that once the front is set, if you turn in, it’s going to go where you point it. Love that about the car now.

[SSLance]

I just realized that I had not posted my report of my first autocross with the new Ridetech shocks installed.

I headed out to our last Autocross of the year that Sunday morning. It was cold, DAMN cold. 27 degrees at my house when I left at 7 am. BRRR… I worked Tech in Heat 0 checking in the competitor’s cars. We had a big crowd show up, 124 drivers total competed in the event. Once the driver’s meeting was over my official work was done so I went to get the car off the trailer and take it out to warm it up. I’m guessing it was about 35 degrees at this time. I took a drive much longer than my usual warm up route to make sure I got some heat into the drive train, then came back, had the car teched then got it into grid ready to roll.

I had left the shocks where I finished with them the day before, my “baseline for slicks” I called it and made my first run. It was probably about 40 degrees at this point. Traction was limited, to say the least. A lot of cars were spinning out in different places searching for grip. My friends watching my run let me know after that I was locking up and sliding both inside rear tires under braking. I didn't notice any wheel hopping though.

Low Speed Rebound -8 Front -6 Rear
Low Speed Compression Little Knob -18 Front -10 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Started here for run #1, 40 degrees, slicks, Locking up rear tires on entry,53.310 +1

The car handled pretty decent, turned in good, slid the back in a couple of places, I chalked it up to cold asphalt, but I texted Ron with a report and he had me add 2 clicks to the Low Speed Compression front and take 2 clicks out of the Low Speed Compression rear. BTW…how freaking cool is it that I can call Ron, on a Sunday, in between runs and ask for tuning advice…

We had a LONG delay before my second run, trouble with the timing lights. I was actually in the car with my helmet on in the staging lane for about 30 minutes before we finally ran. Like what used to happen to me when I played golf on a Saturday afternoon on a crowded course, I was anxious to run and when it finally came time to drive, I shanked it. Looking back at the video, I over drove it everywhere, like a bull in a china closet culminating with me losing the back in the long sweeper and spinning the car out.

Low Speed Rebound -8 Front -6 Rear
Low Speed Compression Little Knob +2/-16 Front -2/-12 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Made adjusts for run #2, long delay before start, over drove everywhere, spun in sweeper,loose on roll through 70.386 +1

I texted Ron, told him what happened. He asked what the car needed to be better and I told him the nut behind the wheel needed tightening. Lol He asked again and I told him I thought it was still loose in the middle roll through. He suggested adding 1 more click stiffer on LSC front and 1 click softer LSC rear, which I did.

Car drove much better on my third run, I drove in a little bit too deep into the first 180 but instead of turning in before it slowed down, I just waited til I knew it would stick, then turned in. I didn't slide it, but gave up a bit of time making the corner longer than it needed to be. The next few turns were uneventful, fast and tight. I had one of the veterans of our Region riding with me for the first time and as I made the gate into the slalom on the back stretch he commented “Damn Lance, NICE!!” that made me feel pretty good, both for the car and the driving. I swung too wide coming out of the last cone of the slalom and had to juke back left to miss the gate and I lost the back of the car for just a bit, it gathered right back up nicely, but it set me up a bit inside on the sweeper, so I had to turn back out, then back in again in the middle and lost a bit of time in the sweeper again because of this. The rest of the run was good. Man this car turns…

Doug said to me “it feels just like an autocross car…”

Low Speed Rebound -8 Front -6 Rear
Low Speed Compression Little Knob +1/-15 Front -1/-13 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Made adjusts for run #3, over drove first entry, Car stable though, lost back end of slalom driver error, little loose roll through, pretty good though 53.140

I wanted to leave the car like it was and try again; Ron wanted to give me a little bit more confidence in the car. At the last minute we decided to take 2 more clicks out of the Low Speed Compression rear…I actually did this with my helmet on as I was about to pull off the grid.

In other events, typically I’ll have a run where I slow down and get real deliberate with all of my turns making sure I hit all of my marks. I told myself several times… “slow down to go fast”. The run felt real clean, never slipped, totally in control, thought I hit my marks and followed the line I need…and most importantly didn't loose the rear in the sweeper which had been plaguing me all day. I felt pretty good coming through the lights…til I saw the timing light. I slowed up about 8 tenths. I slowed down…to go slower.

Low Speed Rebound -8 Front -6 Rear
Low Speed Compression Little Knob -15 Front -2/-15 Rear
High Speed Compression Big Knob -12 Front -24 Rear
Notes: Run 4, pretty good all over, Driver slowed down to go fast, went slower, 53.981

I was disappointed to say the least, I wanted to get into the 52s. The car had it in it, I just didn't get it there. That’s what’s so tough about SCCA Solo events, you only get 4 shots at a course, and it’s done. Had I ran another heat, especially if it was heat 3 when the temps were in the 60s, I might have even got it into the 51s. The car was THAT GOOD after the adjustments made to Ridetech shocks with Ron's expert help.

Here are the videos of the 4 runs

http://youtu.be/lEHTS6XoM2E

I now have a 3 binder notebook that I’ll keep in the car with these notes including my baseline setup and where I ended up after the event just in case I ever find myself out to lunch and have to revert back. I'll also start fresh with a note sheet at every event.

I laminated copies Ron’s shock tuning guide posted above and put page 1 inside the front sleeve of the notebook and page two inside the back sleeve to have for quick reference as well. There are INVALUABLE tools to have for anyone running triple adjustable shocks IMHO.

[AutoX_a_Truck?]

I was disappointed to say the least, I wanted to get into the 52s. The car had it in it, I just didn't get it there. That’s what’s so tough about SCCA Solo events, you only get 4 shots at a course, and it’s done. Had I ran another heat, especially if it was heat 3 when the temps were in the 60s, I might have even got it into the 51s. The car was THAT GOOD after the adjustments made to Ridetech shocks with Ron's expert help.

I was in the same boat. I finally found some speed on my last lap and managed a 52.082 +1 (2.2 seconds faster than my best lap so my quickest lap was dirty!). I think the Scout was probably capable of running a high 50 (especially once the course warmed up) even if I wasn't. It was a fun event to wrap up the season and your Monte Carlo looked really good out there. It's always nice when a setup finally starts to click and hard work pays off.


I laminated copies Ron’s shock tuning guide posted above and put page 1 inside the front sleeve of the notebook and page two inside the back sleeve to have for quick reference as well. There are INVALUABLE tools to have for anyone running triple adjustable shocks IMHO.

Ron's guide is super useful. I will definitely get some use out of it. Thanks Ron!

[SSLance]

Thanks Tyler. I never noticed, did you drive with the corn costume on or take it off to run? :poke: That cracked me up... It was a great event, couldn't' believe the turnout.

I'm putting some 162# springs in the rear tonight and will hopefully get some more parking lot tuning done Saturday before I pull down to Wichita first thing dark and early Sunday morning to run in their last event of the season.

You know I want to run this car more pretty badly to pull it three and a half hours one way just for 4 more runs before the season ends for the year. :naughty: :drive:

[AutoX_a_Truck?]

Thanks Tyler. I never noticed, did you drive with the corn costume on or take it off to run? :poke: That cracked me up... It was a great event, couldn't' believe the turnout.

Haha, I drove down to the event and made my 1st run with the corn costume on, but it was a bit constricting/distracting so I took it off for the rest of my runs. I am glad I wore it on the trip down because the Scout doesn't have a heater.


I'm putting some 162# springs in the rear tonight and will hopefully get some more parking lot tuning done Saturday before I pull down to Wichita first thing dark and early Sunday morning to run in their last event of the season.

You know I want to run this car more pretty badly to pull it three and a half hours one way just for 4 more runs before the season ends for the year. :naughty: :drive:

I can sympathize with that sort of dedication. I currently live in the DC area for school so when I can make it back I usually fly in to autoX, err I mean visit my family.

[Ron Sutton]

I was in the same boat. I finally found some speed on my last lap and managed a 52.082 +1 (2.2 seconds faster than my best lap so my quickest lap was dirty!). I think the Scout was probably capable of running a high 50 (especially once the course warmed up) even if I wasn't. It was a fun event to wrap up the season and your Monte Carlo looked really good out there. It's always nice when a setup finally starts to click and hard work pays off.



Ron's guide is super useful. I will definitely get some use out of it. Thanks Ron!



You're welcome. If you get stuck on something, feel free to ask questions.

[eric1967]

Lance & Ron
I want to thank you guys for all the time & info in these posts. I have been reading this for about a month. Now that the autocross season is over I am getting reading to gather all the measurements from my car. We are not that far apart Lance, maybe we can meet up at an event or two next year. Thanks Eric