Let's talk anti-roll bars

[Ron Sutton]

This post topic moved to another thread here.

[SSLance]

All I need now is for Ron to explain "wedge" and I'll have everything I need to go NASCAR racing... ;)

Seriously, does anyone else feel like they are stealing by reading all of this information here on a free public forum?

Props to you Ron!

[Matt@BOS]

Hey Ron, I have another round of questions for you.

After giving your opinion of what would be a close to optimal setup, I was a little curious about your opinion about how much spring is needed to support the weight of a car. Do you like pre-load on springs, or not. What effect does it have? If you wouldn't mind elaborating a little bit more, I'm sure it could benefit us all.

The reason I ask is because you recommended 450lb springs up front, and 250lb springs out back. The front springs and .250" sway bar with my current setup have not been able to control the roll to a degree that I've been happy with, and tend to settle so much that I would need to run a longer spring than I can fit on the coilover without compressing the longer spring to get in under the shock collar.

Matt

[Ron Sutton]

All I need now is for Ron to explain "wedge" and I'll have everything I need to go NASCAR racing... ;)

Seriously, does anyone else feel like they are stealing by reading all of this information here on a free public forum?

Props to you Ron!

I'm taking a little time off from racing ... before I tackle my next project ... and I enjoy sharing & helping if someone is actually going to use it.

Were you serious on the"wedge" question ... or just being funny?

[Ron Sutton]

Matt, I need some more clarity,

Hey Ron, I have another round of questions for you.

After giving your opinion of what would be a close to optimal setup, I was a little curious about your opinion about how much spring is needed to support the weight of a car.
I'm NOT clear on what you're asking. Can you re-phrase this?

Do you like pre-load on springs, or not.
Until I read further down, this question confused me more ... because all springs are preloaded with the weight of the car.

What effect does it have? If you wouldn't mind elaborating a little bit more, I'm sure it could benefit us all.
Again, all springs get preloaded with the car's weight & I'm not clear on what you're asking. Are you asking ... is there a problem with running a spring that has to be compressed to install it on the shock? or ... ?

The reason I ask is because you recommended 450lb springs up front, and 250lb springs out back. The front springs and .250" sway bar with my current setup have not been able to control the roll to a degree that I've been happy with,
OK. Let's discuss higher rate sway bars & springs. But I need your shock mounting motion ratio & shock angles to do this correctly.

and tend to settle so much
What do you mean settle? "Settle" in spring lingo ... means the springs started out a "X" free height (no load) ... and after being installed and used ... are now a shorter free height when removed. Is that what you mean? Or are you calling the compression of the spring with the car's weight "settling" ... when in fact their free height is the same as before?


that I would need to run a longer spring than I can fit on the coilover without compressing the longer spring to get in under the shock collar.
Two things ...
1. Why would you need to run a longer spring?
2. When you ran this spring before, did the car sit too low?

[SSLance]

Truthfully I always wondered exactly what the nascar teams were talking about when discussing putting wedge into the car?

[j-rho]

Moved here for Matt's sake

[Ron Sutton]

WoooHoooo !!

My little buddy AJ Allmendinger won the NASCAR Nationwide race at Road America!

Couldn't be happier for him. He needed something good to happen.

[Ron Sutton]

Truthfully I always wondered exactly what the nascar teams were talking about when discussing putting wedge into the car?

Hi Lance,

"Wedge" is a Stock Car term meaning the same thing as "Cross Weight" used by Road Racers & Open Wheel Racers, even in oval racing. Some racers simply shorten it to "Cross" ... as in "put some cross in the car". Then throw in a mix of Engineers and it's a wonder any of them understand each other.

I have to go back & forth because I've been involved heavily in different forms of oval & road racing. I find it amusing the terms are so different. One of them you & I have been discussing is KPI & SAI. Stock car guys still use the KPI term, but Double A-arm cars don't have king pins.

Anyway, let me explain what Wedge & Cross Weight are ...

If we were going road racing, and the rules allowed, we would be running the car as weight balanced side-to-side as we could get it. Here is a car that weighs 2572#, with a 48.77% front weight & 51.23% rear weight.

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Example #1

If we could achieve it, the 4 scales would read ....

LF 626 # RF 626 #
LR 660 # RR 660 #

This is a car with no wedge or cross weight.

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Example #2

If that same car was on the scales & read ...

LF 616 # RF 636 #
LR 670 # RR 650 #

You'll notice the LR & RF corners weigh more than the RR & LF. That is wedge or cross weight. In this example, the front wheels have a 20# difference between them ... as do the rear tires. That's not much, but not optimum. Not counting other aberrations in the suspension, this car would have a little more grip on left hand turns & a little less grip on right hand turns.

It's not much, but when you're racing and driving the car at 102% & the tires are at their optimum slip angle ... with no room to spare ... 20# would make a small difference that would affect the car "a little" & a talented race driver would feel ... and be whining & screaming for a change.

OK, just kidding on the whining & screaming ... sorta. You NEED the driver to give accurate, precise, measured feedback in a consistent, methodical way to know when to tune, which direction to go & how much. The difference between "whining" & "constructive input" comes down to attitude & communication skills ... and varies from driver to driver.

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Example #3

LF 636 # RF 616 #
LR 650 # RR 670 #

If it were reversed ... and looked like the #'s above ... again not counting other aberrations in the suspension, this car would have a little more grip on right hand turns & a little less grip on left hand turns. If the car handling was "neutral" on right hand turns, it would be a bit looser on left hand turns. If the handling was "neutral" on left hand turns, it would be a bit tighter/pushy on right hand turns.

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Example #4

Both examples #2 & #3 show SMALL amounts of cross weight difference. Bigger differences in corner weights make bigger differences in the results, but the effects are the same.

LF 736 # RF 516 #
LR 550 # RR 770 #

If the differences were larger ... like the example above ... the handling differences from right turns & left turns would be HUGE.

If the car handling was "neutral" on right hand turns, it would be a VERY loose on left hand turns. If the handling was "neutral" on left hand turns, it would be VERY pushy on right hand turns.

By the way, this example is not a simple tuning adjustment.

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In most cases, it is undesirable to have any cross weight for road racing or AutoX cars. There are exceptions.

Years back, we raced at a shifter kart track that had a LOT of fast right handers & only 2 lefts. 1 of the left turns was banked ... which gave more grip ... and the other left hander was a tight hairpin. We dialed in cross weight the opposite of an oval track car, so it had more grip on right hand turns. The banked left hander was still good. And the karts were loose in the hairpin ... which we used to our advantage, rotating the rear end to help the karts turn. That set-up dominated there the 2 years we ran it.

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Example #5

LF 516 # RF 736 #
LR 770 # RR 550 #

So, the casual observer may think oval track racers simply add "wedge" and it would look like this.

You calculate how much wedge or cross weight a car has ... by adding the opposite corners of LR & RF & compare it the car's total weight.
The LR 770 # + RF 736 # = 1506# / Total: 2572 # = 58.55% wedge or cross weight.

* Example #4 would be described as having 41.45% wedge or cross weight.

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But that's not how an oval track car would look on the scales ...
because they are allowed to race with a higher left side weight balance. Each series or class has a rule written as either a left side percentage maximum, a left side pound maximum or specific rules about where weight can be put.

In Professional Road Racing & Oval Track Racing, car designers & builders build the cars as light as they can ... and still be structurally sound ... so they can put the weight (lead or tungsten) where they want it. Low, left & centered in the wheelbase for Oval Track ... Low & centered for Road Racing.

Here is what the scales would read for a real world oval track car with rules calling for a Maximum of 58.0% left side weight, if it still had the same & 51.23% rear weight we have been using in the previous examples.

LF 616 # RF 637 #
LR 880 # RR 436 #


This car weighs a total of 2572# ... with driver & 175# Lead
Target Cross: 59.0% w/ARB preload
* It was 57.5% before preloading the front ARB

Left side weight: 58.2%
Front weight: 48.77%
Rear weight: 51.23 %

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So when a Stock Car team is calling for more wedge, they are turning a threaded adjuster "in" on the LR or "out" on the RR ... that is to give the car more grip. If they're calling for less wedge, they are turning a threaded adjuster "out" on the LR or "in" on the RR ... that is to free the car up (less grip).

They do both of these through the back window.
* The right side of the track bar is also adjustable through the back window.

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Oval track racing is way more challenging than outsiders know. I love all forms of motor racing ... but I prefer road racing the most.

[Ron Sutton]

This post topic moved to another thread here.

[j-rho]

Moved here for Matt's sake

[diesel25lrs]

Ron,
Thank you so much for sharing your knowledge! I've been asking many of these same questions & basically have the exact same issues as Matt but with a Speed Tech torque arm setup... My build started as a restoration that quickly turned into auto-x racer & wondering why the "REALLY" bad push in corners...everyone would just tell me to slow down going into corners...yes- some of it is inexperience driving but i feel it was more the cars bad setup...The car wasn't built correctly from the start for racing(275F/345R tires & stock spindles)...with almost everyone on the auto-x scene switching to wider fronts the last year it really got me thinking about my setup & reading this has really confirmed where i need to start making improvements to go faster! So i dont highjack this thread- i'll reread everything again & go along for the ride! I would like to get back with you at a later time with my specs for setup if possible? Thanks for breaking everything down!
Josh

[Ron Sutton]

Ron,
Thank you so much for sharing your knowledge! I've been asking many of these same questions & basically have the exact same issues as Matt but with a Speed Tech torque arm setup... My build started as a restoration that quickly turned into auto-x racer & wondering why the "REALLY" bad push in corners...everyone would just tell me to slow down going into corners...yes- some of it is inexperience driving but i feel it was more the cars bad setup...The car wasn't built correctly from the start for racing(275F/345R tires & stock spindles)...with almost everyone on the auto-x scene switching to wider fronts the last year it really got me thinking about my setup & reading this has really confirmed where i need to start making improvements to go faster! So i dont highjack this thread- i'll reread everything again & go along for the ride! I would like to get back with you at a later time with my specs for setup if possible? Thanks for breaking everything down!
Josh

You're welcome Josh. After you re-read all the tech stuff ... if you have questions pertinent to this thread ... feel free to chime in here. If you have questions concerning your car & specific handling issues & solutions, let's start a new thread.

What part of NC are you in? I travel to the Mooresville & Concord area occasionally.

[diesel25lrs]

Ron,
Sounds great! I'm just south of Raleigh about an hour in Pinehurst. M-ville is only 2hrs from here... You must be doing some NASCAR tar testing over that way...

[RobNoLimit]

great info Ron. I enjoyed talking with you in P-town (I have the red C10) Thanks for helping out. Some of the tuning points for Matt have me thinking.

[Ron Sutton]

Ron,
Sounds great! I'm just south of Raleigh about an hour in Pinehurst. M-ville is only 2hrs from here... You must be doing some NASCAR tar testing over that way...

Josh,

That was funny. No, we're not doing "Tar testing".

I still work with Penske, Roush, RCR & Gibbs on sponsorship stuff I can't discuss publicly. I expect to fly back there again in August. Often I fly into RDU because I have a zillion Southwest Air points & they don't fly into Charlotte. Flying into RDU makes it easier to go to RCR first, then spend my time in Concord, Huntersville, Mooresville, etc. I like to stay in Concord, by the Mall, because there are so many restaurants and it's close to the dirt track, Concord Speedway's two tracks & the big Speedway.

Is there any cool ProTouring stuff or AutoX going on back there?

[Ron Sutton]

great info Ron. I enjoyed talking with you in P-town (I have the red C10) Thanks for helping out. Some of the tuning points for Matt have me thinking.

Hi Rob !

I enjoyed talking with you too. I love your truck. My best buddy has a sweet '69 C10 short fleetside that I have first dibs to buy when he's ready to sell. I'll probably paint it red & black, since those are my colors.

You have a great chassis & suspension package. I would love to work with you on set-up and/or geometry stuff ... and go do some test days if you want. We might find a few more tenths with some TLC.

[diesel25lrs]

Ron,
Yeah-thats the racer's haven over there! Let me know when your coming for sure & i'll cruise the hotrod up & grab some dinner with you!

We have a few good races around here- RTTOS in SC, RTTH- pigeon Forge, TN, GG-Charlotte & of course DSE HQ is just outside of Charlotte- must see if u haven't been there yet! I have about 4 good friends within an hour of me that all have PT cars so the scene is not huge but growing here!

[Ron Sutton]

I'll do that. Take care.

[Ron Sutton]

Matt sent me a PM, and said I could post it to respond so everybody could learn from what we’re discussing.

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Hey Ron, Let me provide you with a little more clarity. I apologize if my terminology is incorrect. Most of us come from a hot rodding, show car building, or cruising background and it is only in the last several years that we've started to realized how much fun it is to try and go fast, at least that is the case with most of us southern California guys. I think we have probably come up with some of our own terms as we go.

What I meant by pre-load was the amount of load placed on the spring before the car is ever placed down on its own weight, or how much I need to compress the spring before I put the coil over back in the car.
Gotcha. I understand what you’re saying now.


For example, on the front, with 450lb springs I would need to tighten the collars way up so that the spring is already moderately compressed in order to keep the car from sitting too low. If I only ran the bottom adjustment collar up to the spring before setting it in the car, the car would sit far too low. Does that make a little more sense.
Yes. I’m clear now.


Perhaps I need a longer spring?
The question to get answered for both of us is … if you compress either front suspension corner … does the spring run out of travel first or the shock? Then that will guide me on what to suggest.


Also I have noticed that with the lighter springs, 450 and 550 that the car would sit lower after the car was driven on the track for the first time. I could drive 200 miles and ride height would stay the same, but after an afternoon at the track the front would sit half an inch lower, and stay there permanently. Is that normal?
It is normal on low quality springs. Most … but not all … of the $50-75 springs typically do that. What brand of springs are your 450#’s? … what brand are the 550#’s ?


I think from my seat time the car felt undersprung (at least to me). With about a degree of static negative camber I was still chewing up the outside of my front tires.
This is partially a Roll Angle issue … to be worked out with springs & sway bar … and partially a KPI/Caster split issue.

Your DSE setup is WAY better than factory, but doesn’t currently have enough caster to be optimum for AutoX cornering level performance. I’ll expand on this, but you will want to refer back to the post I made on KPI/Caster Split for it to completely make sense. DSE and many others top companies building clips use the Corvette C6 spindle which has 9.15 degrees of KPI. To dial that front end to CARVE tight corners, we need around 1.0+ degrees more caster then the KPI angle.

The ZR1 C6 Corvettes that run this spindle have a factory caster setting of 7.7 degrees up to 8.3 degrees … for factory production street cars. All of the savvy Corvette guys that compete with these cars, run the caster at 10.0 to 10.5 degrees … then make the camber around -1.5 … and kick butt.

I am not sure why the clip companies reduce their standard caster setting below factory specs, but probably have good reasons for it. For performance, I would think they would run the factory setting the spindle was designed for … around 8 degrees, but again, they may see other reasons not to. If we want it to really kick ass in AutoX, need to use the settings Corvette racers use (-10.0 to -10.5 degrees).

I don't have permission to say who … but several winning AutoX guys … run a LOT of caster. Matt, currently, at 5.0 degrees of caster, your KPI/Caster split is 4.15 degrees favoring the KPI. To achieve optimum tire contact patches … the KPI/Caster split needs to be 1.0 or more degrees favoring the Caster.

Having said that, I’m not sure your current DSE package can “get to” 10+ degrees of caster … and that’s ok. Let’s just make it better than it currently is. If you can get yours up to 7-8 degrees of caster … and set the static camber around -2.0 degrees … you won’t be folding the tire under like the car in the attached photo.