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    1. #21
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      Need a little help figuring something out

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



    2. #22
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      Got the car back on the lift last night for the first time since the runs with the slicks...





      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/0B1Fn...RzV0dWcEE/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.
      Lance
      1985 Monte Carlo SS Street Car

    3. #23
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      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.
      Lance
      1985 Monte Carlo SS Street Car

    4. #24
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      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?

    5. #25
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      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.
      Lance
      1985 Monte Carlo SS Street Car

    6. #26
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      This thread is about Measuring & Modifying Your Front Suspension Geometry:
      For a thread focused on: Overall Handling & Tuning for Track Performance ... click HERE.
      For a thread focused on: Front Suspension & Steering Geometry for Track Performance ... click HERE.
      For a thread focused on: Rear Suspension & Geometry for Track Performance ... click HERE.
      For a thread focused on: Designing Aerodynamics for Track Performance ... click HERE.
      For a thread focused on: Safety for Pro-Touring Track Cars ... click HERE.
      For a thread focused on: Brake Selection ... click HERE.


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

      Cool Lance!

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

      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

      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.



      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.
      Last edited by Ron Sutton; 12-07-2014 at 02:04 PM.

    7. #27
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      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 …


      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.

      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.

    8. #28
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      Solutions:

      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).

      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.

      Name:  KPI-SAI.jpg
Views: 2972
Size:  39.9 KB



      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.

      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.

      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.




      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.

      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.

      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
      Last edited by parsonsj; 06-12-2013 at 06:46 PM. Reason: User request

    9. #29
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      be back in a year i have to try and learn what ron just said haha.
      Mopar or no Car
      Your either with us or Behind us

    10. #30
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      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.

    11. #31
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      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
      Lance
      1985 Monte Carlo SS Street Car

    12. #32
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      Quote Originally Posted by Ron Sutton View Post
      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?
      Lance
      1985 Monte Carlo SS Street Car

    13. #33
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      Quote Originally Posted by Ron Sutton View Post
      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.
      Lance
      1985 Monte Carlo SS Street Car

    14. #34
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      Quote Originally Posted by Ron Sutton View Post

      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**
      Lance
      1985 Monte Carlo SS Street Car

    15. #35
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      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?
      Lance
      1985 Monte Carlo SS Street Car

    16. #36
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      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?
      Lance
      1985 Monte Carlo SS Street Car

    17. #37
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      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.

    18. #38
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      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.
      Lance
      1985 Monte Carlo SS Street Car

    19. #39
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      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.







      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.




      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?
      Lance
      1985 Monte Carlo SS Street Car

    20. #40
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      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.
      Lance
      1985 Monte Carlo SS Street Car

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