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    1. #1
      Join Date
      May 2011
      Location
      Northwest, MO
      Posts
      101
      Country Flag: United States

      Suspension Optimization and Tuning Help

      After seeing several of Ron’s very educational threads I decided that it was time to put in some extra work and go to the next level and try to optimize my less than ideal budget setup. Here is a basic breakdown of my vehicle.

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      1972 International Scout II
      T: 2,805 lbs (F: 1,460 lbs & R: 1,345 lbs)
      F: 52%
      R: 48%
      (These are close estimates based on less than ideal four corner scales, which were downhill and showed 53% & 47%. I am in the process of getting more accurate up-to-date weights)
      Wheelbase: 99.75”
      FT: 57.8375”
      RT: 57.25”
      Ride Height Behind Front Tire: 4”
      Ride Height Center of Crossmember: 4.25”
      Estimated CG Height: 12” (That's the height to the center of the harmonic balancer, but I am not sure that is entirely accurate for my vehicle)
      Front Tires: 315/35/17 Nitto NT05 on 17x11” (11.5” tread width)
      Rear Tires: 335/35/17 Michelin Pilot Sport 2 on 17x12.5” (12.5” tread width)

      Front Suspension:



      The front suspension is S10 based with a combination of aftermarket and stock style parts. It’s a basic stock style 2” drop spindle, with a larger stock style 33mm sway bar from a newer model and ridetech PosiLinks.

      The tubular upper control arms are from a swap meet and apparently were designed for a metric dirt car, but have been modified. The upper arms use Allstar Adjustable ball joints adjusted approximately 1” from the tallest setting.

      The lower control arms are ridetech StrongArms with the standard Moog ball joint.

      The upper spring pocket has been removed to fit a 4.1” stroke RideTech Triple Adjustable Coilover with 4.1” stroke (10.125” compressed & 14.225” extended) running a 10” tall 2.5” ID 450 lbs/in spring.

      I believe that my front suspension might possibly be considered a “Tweener” set up or at least it might be possible to set it up as a Tweener. Taking actual shock travel measurements at an event or by simulating event conditions is a priority once the weather is better. But for now I can only estimate based on videos and jouncing the front end that my front shocks can compress about 2.5-2.75” under heavy braking and are nearly bottomed out when the front cross member scrapes.

      I typically shoot for about -1 degree of static camber, 0 toe in/out, and according to the FasTrax Adjustable Caster Camber Gauge I can currently register about 8.5-8.6 degrees of caster.

      I am also battling a relatively high scrub radius due to my 17x11” wheels with just 4.25” backspacing. Using the method in Lance’s thread, I measured the scrub radius at 4 13/32”

      A few videos for reference:

      http://www.youtube.com/watch?v=R9o9U...urp7H6zsMZlgX7

      http://www.youtube.com/watch?v=ISMsvaYOpuE

      An older video with the ‘47 truck body, but same basic setup with similar front weight. In this video the fender drag quite a bit because I had a tall passenger riding shotgun.

      http://www.youtube.com/watch?v=t3Jg_RBur7Q

      Here’s a really tight GG course where I struggled with tons of push in the middle of the corner.

      http://youtu.be/2RlgucBBqO4?t=1m8s

      Steering:

      The S10 spindle steering arm geometry has always annoyed me because it’s front steer and the arm is actually angled forward toward the centerline of the front of the frame because the tie rod must clear a tire (for small diameter stock style wheels) or in my case the wheel itself. Moving the tie rod end outward any further will require shortening the steering arm at least an inch or two so that it can clear the rim lip and barrel, but I have not quite been able to determine whether this is feasible or not. I have a 12.7:1 Grand Cherokee steering box. The stock spindle steering arm has a flat base at the end where the tie rod end mounts, but there was room for moving the mount back slightly, which effectively shortened the arm with good results.

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      Rear Suspension:

      Homemade truck arms with a single front pivot point (spherical bearing). The truck arms are mounted solid to the axle pad underneath the axle tube with RideTech Triple Adjustable Coilovers mounted behind the axle. It has an adjustable pahhard bar.

      After reading the mapping instructions, and then rereading them again, my dad and I spent the better part of two days developing creative ways to map out the front suspension. There were small, but mostly consistent variations side-to-side, but we double checked each measurement and/or checked against a different measuring method in some cases. I have those measurements in a spreadsheet. Thus, if possible, I would like to set and tune the front roll center height.

      I primarily want to excel at autoX and tighter corners. I drive to events, but comfort is largely not an issue as long as the setup is not so harsh on wear parts that a 200 mile trip is out of the question. I also occasionally run track days, where I think the Scout feels much easier to drive than on a tight autoX course, but I do these mostly just for fun. At Mid-America Motorplex I was not running 10/10ths by any means as it was only my 2nd time on course, I have very little formal training, and I do not have anything near a racecar level of safety gear. Anyway, once I was a bit braver at the end of the day my quickest timed and recorded lap with Harry’s Lap Timer was 1:47. One of the quickest times I logged without a video was nearly a 1:46 flat with a gear limited top speed of 128 mph on the main straight. I am told that a good driver with a stock C6 Z06 should run in the realm of 1:45.

      I favor running a modern high travel/low roll setup if possible, but I think I would currently fall into a tweener setup.

      As I was reading through some of the helpful threads I came up with a few general goals based on what I have read so far:

      1) Map the roll center and correct problems shifting towards a high travel/low roll setup if feasible
      2) Correct and potentially improve LCA geometry
      3) Correct and potentially improve UCA geometry
      4) Build in Ackerman steering (I think but am not certain that my steering geometry is a huge hinderance on tight autoX courses)
      5) Dial in caster and caster gain
      6) Determine if more sway bar is necessary
      7) Determine if spring rate changes are necessary
      8) Possibly revalve my Ridetech coilovers if appropriate
      9) Properly dial in and adjust my coilovers
      10) Learn as much as possible
      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...


    2. #2
      Join Date
      Nov 2012
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      Sounds like a plan Tyler.

      Can you convert your excel spreadsheet into a JPG file & post it up? If you have Photoshop or Adobe Pro, those will do it. Otherwise, you'll need to post them up manually.

      Also, I'd like to see more photos showing all angles of your rear suspension & steering. Post some of bottom view, side view & front or rear view.

      A few questions for you to answer ...
      1. Is that an aftermarket spindle? It looks kind of like a CPP.
      2. Does each truck arm have its own pivot or do the two arms join at the front forming a triangle like old Model A suspensions?
      3. Get a height measurement to the front pivot(s) of the truck arms.
      4. Get a height measurement to the mating surface of the truck arms & the housing brackets.
      5. Did you measure motion ratios of the springs? If not, please do.
      6. List the spring rates front & rear.
      7. Have you calculated effective rates on the sway bars? if not, I'll show you how, but I need photos showing me the shapes.


    3. #3
      Join Date
      Oct 2010
      Location
      Mena, AR
      Posts
      287
      Country Flag: United States
      This should be a good learning experience for us all.

      Looking forward to reading it.

      Chris


      Chris
      1967 ElCamino
      2004 Chevy SSR (my sons)
      1951 Chevy pickup(my sons)

      1967 Elky https://www.pro-touring.com/showthre...587-Evil-Angel

      1951 truck https://www.pro-touring.com/threads/...3-year-old-son

    4. #4
      Join Date
      Aug 2012
      Location
      Peoria, AZ
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      1,757
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      Subscribed...

      I've seen this truck\car\SUV Scout thing run in person and it is impressive. I'm certain with Ron's tutulage and Tyler's fabrication skillz and driving it'll only get faster.
      Lance
      1985 Monte Carlo SS Street Car

    5. #5
      Join Date
      May 2011
      Location
      Northwest, MO
      Posts
      101
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      Sounds like a plan Tyler.

      Can you convert your excel spreadsheet into a JPG file & post it up? If you have Photoshop or Adobe Pro, those will do it. Otherwise, you'll need to post them up manually.

      I see the spreadsheet JPG did not work the first time so I had to reattach it as a PDF.

      Suspension Pivot Point Mapping Worksheet Scout II v.Final.pdf UPDATED on 2/14/2014 because there was a round off error for the Passenger Lower arm rear pivot.

      Also, I'd like to see more photos showing all angles of your rear suspension & steering. Post some of bottom view, side view & front or rear view.

      Here are some pictures I have on hand of the steering and rear suspension. For the rear suspension, obviously it was easier to use a few older pictures from earlier in the build. I can try to get some better views if necessary.

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      Ignore the wide spacer on the front end. That was just a mockup for a narrower set of front wheels that I used on the street with the truck body.

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      For the steering, I also included an older picture of center link and tie rod setup too because it was slightly better.

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      A few questions for you to answer ...

      1. Is that an aftermarket spindle? It looks kind of like a CPP.

      Yes, the spindles are generic aftermarket drop spindles, but I do not know what brand they are. I bought them used. If the brand is important I might be able to find some identifying marks, but I did not see anything obvious such as part numbers or markings.

      2. Does each truck arm have its own pivot or do the two arms join at the front forming a triangle like old Model A suspensions?

      The two arms join at the front forming a triangle. It is 48” from the center of the pivot point to the center of the axle.

      3. Get a height measurement to the front pivot(s) of the truck arms.

      5 3/8”

      4. Get a height measurement to the mating surface of the truck arms & the housing brackets.

      10 1/2”

      5. Did you measure motion ratios of the springs? If not, please do.

      I quickly searched through a few of the threads here and at Lateral-g, but I did not find a definitive gold standard method for measuring the motion ratio in the front suspension thread. In the past, I have used the simple method of distance from LCA pivot center to shock mount divided by LCA pivot to center of ball joint. Currently, works out to 0.578 (8.5/14.7), but I am open to suggestions on gathering a better measurement.

      6. List the spring rates front & rear.

      Front: 450 lbs/in
      Rear: 150 lbs/in


      7. Have you calculated effective rates on the sway bars? if not, I'll show you how, but I need photos showing me the shapes.

      In the past I have tried a few methods I have seen online to get a rough estimate, but I do not have accurate numbers. Here are some pictures of the sway bars. The front is what the larger (33mm on the bottom) looks like compared to the original in the top picture. The bottom picture shows the rear sway bar, which is 32" long with 8 5/8" arms that have some adjustment.

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      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...

    6. #6
      Join Date
      Nov 2012
      Location
      Sacramento, CA
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      A few quick questions before I get started ...

      1. Is there a bushing or monoball in the front pivot point of the rear suspension triangle where it connects to the frame?
      2. With no bind or even pressure ... how far will the rear end housing articulate (angle difference to the frame) each direction ?
      3. Front sway bar: What diameter? Solid? If hollow, what wall thickness?
      4. Rear sway bar: What diameter? Solid? If hollow, what wall thickness?


    7. #7
      Join Date
      Oct 2011
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      Philipsburg, Pa
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      527
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      Anything Ron works with gets faster. Or better. Or whatever the goal is.

      Subscribed.
      Technical Support
      UMI Performance, Inc.
      [email protected]
      814.343.6315

      Join us on Facebook!

    8. #8
      Join Date
      May 2011
      Location
      Northwest, MO
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      A few quick questions before I get started ...

      1. Is there a bushing or monoball in the front pivot point of the rear suspension triangle where it connects to the frame?

      It is a Ύ” spherical bearing pressed in a tube. There is probably a possibility of bind at extreme articulation, but I have not seen any evidence of that during testing or inspection.

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      2. With no bind or even pressure ... how far will the rear end housing articulate (angle difference to the frame) each direction ?

      When we designed the rear end and installed the ridetech Coilovers it was possible to hold either end of the axle against the frame (max compression travel) with the opposite end at full shock extension (with no springs installed) without bind. I do not think this amount of articulation would ever occur in the real world except maybe to a much smaller extent when driving one wheel at a time into a steep gas station entrance. If exact angles are needed I can do some tests to measures those, but that will probably have to wait until the weekend.

      The only time I have seen a similar setup in use was on an Agent 47 Mustang prototype. It appears to have a more sophisticated front pivot, but the picture is too small to tell exactly what it is.


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      The old body design with an open truck bed was more conducive to taking video. I am not sure how helpful they are, but here are a few:

      http://www.youtube.com/watch?v=PtI0E8eP8uk

      http://www.youtube.com/watch?v=sDqM7FISJeM

      http://www.youtube.com/watch?v=uCbXzO0cvts

      http://www.youtube.com/watch?v=kdTxTR-Zdyg


      3. Front sway bar: What diameter? Solid? If hollow, what wall thickness?

      33 mm solid

      4. Rear sway bar: What diameter? Solid? If hollow, what wall thickness?

      7/8" solid
      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...

    9. #9
      Join Date
      Nov 2012
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      Sacramento, CA
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      Excellent. Thanks for those answers & the video.

      I'll input all the data & be back on here in a few days. Would you measure the height from the ground to the CL of the rod end on each side of your panhard bar & post for me?


    10. #10
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      May 2011
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      Northwest, MO
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      Excellent. Thanks for those answers & the video.

      No problem. I really appreciate your help!

      I'll input all the data & be back on here in a few days. Would you measure the height from the ground to the CL of the rod end on each side of your panhard bar & post for me?

      When my dad and I mapped out the front suspension I figured those measurements would be important so they were actually included in the PDF I posted under the row with "Panhard Ride Height" obtained by measuring to the center of the rod ends.

      The axle end (on the driver's side) is 9 5/8" and the frame end (on the passenger side) is 6 5/8"

      The frame side is adjustable upward in 1" increments, with the 6 5/8" height the lowest setting, but modifications could be made to either end if necessary.
      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...

    11. #11
      Join Date
      Jul 2013
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      Hubert, NC
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      I'll be following this one. I LOVE this stuff, as an old round track guy (asphalt) street stock, LLM, Modified. A person can always learn something. Tyler...I'm sure you've already done this. But take notes on Everything. Best of luck on your quest.
      David H. Amrine
      (USMC Retired)

      Boys drive fast on the street. But MEN prove how fast they are at the Track.

    12. #12
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      May 2011
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      Northwest, MO
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      Ron, it might have been obvious anyway, but I went ahead and updated post #5 so that the information regarding the front and rear sway bars is more accurate. The top picture shows the original front sway bar and the current front sway bar look like. The bottom picture shows the rear sway bar, which is 33" long with 8 5/8" arms that have some adjustment.

      Quote Originally Posted by 1966longroof View Post
      I'll be following this one. I LOVE this stuff, as an old round track guy (asphalt) street stock, LLM, Modified. A person can always learn something. Tyler...I'm sure you've already done this. But take notes on Everything. Best of luck on your quest.
      Thanks! I am really digging the Nova in your profile pic. My dad has a '67 SS that he has had since high school that he autocrosses.

      Quote Originally Posted by SSLance View Post
      Subscribed...

      I've seen this truck\car\SUV Scout thing run in person and it is impressive. I'm certain with Ron's tutulage and Tyler's fabrication skillz and driving it'll only get faster.
      Thanks! I hope to run a handful of SCCA events this season and get the Scout dialed in. I was really impressed by your car last season too.
      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...

    13. #13
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      Jul 2009
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      Sackville, NB, Canada
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      Also following this - hoping to get some insight into new avenues for improvement on S10 front ends.
      Tyson
      '95 Firebird Formula: suspension + 315's
      '66 Mustang Coupe, 289

    14. #14
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      now In Dandridge, Tn.
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      This should be fun. We have an S-10 here that we play with. I'll get some picts of the front end fixes. It's only a coil spring but we made big gains. Ron, I have raced with Tyler a few times. He is smart and capable, this should work out well. Tyler, kepp up the good work - see you in a few months.

    15. #15
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      Ron, I just wanted to check in to make sure you had all of the info you needed from my end. Thanks again for your help!

      Quote Originally Posted by RobNoLimit View Post
      This should be fun. We have an S-10 here that we play with. I'll get some picts of the front end fixes. It's only a coil spring but we made big gains. Ron, I have raced with Tyler a few times. He is smart and capable, this should work out well. Tyler, kepp up the good work - see you in a few months.
      Rob, thanks for the kind words. I would really appreciate your valuable input too. I saw a thread for the S-10 over on the Chevy Truck forum. It's a really neat setup and looks cool with the wide tires and body work.
      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...

    16. #16
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      Hi Tyler,

      I've been busy with client design projects the last few weeks & next week too. I'll see if I can carve out some time this weekend to map out your front suspension. But I have reviewed & analyzed your suspension issues.

      I have some observations about Your Scout's handling characteristics that are clear from watching the videos. Thanks for those by the way. As Lance will tell you ... I am very visual ... and need photos and/or videos. I've spent 35 years watching race cars, roll angle, travels & tire angles.

      From your videos, it is clear ...
      a.
      Your Scout has too much roll angle for the camber you're running.
      -OR-
      b. You need more camber for the roll angle you're running.

      c. Your front geometry only provides a moderate amount of camber gain in full dive. Not enough for the high roll angle you're running. So your outside front tire does not have a good contact patch when turning. In fact, when you turn the steering hard & fast, the contact patch narrows immediately. I am estimating about 40-45% contact patch loss. So your outside front tire is going from 11.5" of contact patch ... to 6". Since the rear tires still have a 12.5" contact patch (or close to it) ... the truck goes into an instant push.

      d. The inside front tire has a decent contact patch because ... the inside wheel is losing camber as it lifts ... due to the high roll angle ... which is actually helping it. Often guys have optimized the camber for the outside front tire and have the inside tire working poorly. Your situation is the opposite.

      e. You have a soft spring package which is letting the truck suspension travel a lot. That part I like, but you don't have a happy suspension package.

      f. You have a high degree of roll angle from a combination of weight, higher CG and insufficient sway bar size.

      g. You have a slight mismatch in front & rear roll angles. Ideally we want the front roll angle to be .3° to .4° less roll angle than the rear. This creates a balanced handling competition vehicle that is disengaging the inside rear tire more than the inside front tire. Yours is off a little. It is rolling slightly less in the rear than the front ... I'd say around .2° more in the front ... which is about .5°-.6° from ideal. What this does is keeps the inside rear tire too engaged ... and unloads the inside front tire to a higher degree ... contributing to your push condition.

      h. The final ... but BIG issue, is your front shock valving doesn't have enough low-speed rebound. Meaning the front shocks let the inside front suspension roll too much and come up too quick when you step off the brakes. Ideally for AutoX & road courses, you need the shock valving to "tie down" the front end down through the roll through zone. And when the shocks do "let go" and let the front come up, it needs to happen slower. Otherwise it unloads the inside front tire ... adding to the push condition. You're probably running the shock rebound valving soft for more exit grip, but there are other, better ways of getting exit grip without killing the middle of the corner with a push.

      So, before we get into changing roll centers, camber, caster, etc ... you need to pick a path for your suspension strategy. There are two good routes to go. And each strategy will need a different roll center and have different needs for optimum geometry.

      #1 is a conventional low front travel/high roll angle set-up. You already have the high roll angle. For this, you would need stiffer front spring rates, reduce the compression travel on dive & keep the soft sway bars. Then you'll need to increase the camber gain & caster in the front geometry to work well with the higher roll angle.

      #2 is a modern high front travel/low roll angle set-up. You already have the high front travel. For this, you would need bigger, meaner, stiffer sway bars, reduce the roll angle from the estimated 3° to around 1.5°. Then you "may" need to increase the camber gain & caster in the front geometry ... but not by much. When you roll the truck 1.5° less ... that's adds 1.5° dynamic camber to the outside tire. You will still want to optimize the camber & caster settings, but it won't need as big of a change as it needs with the high roll angle you have now.

      Each has its pros & cons. If you're not clear on them, I'll be happy to provide insight. But if you're clear, pick a path and let's work on the whole suspension package along with the roll center & front suspension geometry.



      Last edited by Ron Sutton; 05-22-2014 at 06:33 AM.

    17. #17
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      Ron Sutton is the singular most helpful source of suspension design and tuning information I've ever seen.

      That is all.

    18. #18
      Join Date
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      Hi Tyler,

      I've been busy with client design projects the last few weeks & next week too. I'll see if I can carve out some time this weekend to map out your front suspension. But I have reviewed & analyzed your suspension issues.

      Ron, thanks for the response. I really appreciate your generous input. I understand you are busy with many other very important projects so no rush, I will wait patiently.

      I have some observations about Your Scout's handling characteristics that are clear from watching the videos. Thanks for those by the way. As Lance will tell you ... I am very visual ... and need photos and/or videos. I've spent 35 years watching race cars, roll angle, travels & tire angles.

      I am amazed at how much information you were able to gather from the videos. These two videos might simply be redundant so I am not sure if they are very helpful, but I figured I would include two more short videos of autoX runs:

      http://youtu.be/tewKtS1f57E
      http://youtu.be/dnA8TmygFLk

      Are there any particular on board shots that would be particularly useful to capture at future events?


      From your videos, it is clear ...
      a. Your Scout has too much roll angle for the camber you're running.
      -OR-
      b. You need more camber for the roll angle you're running.

      c. Your front geometry only provides a moderate amount of camber gain in full dive. Not enough for the high roll angle you're running. So your outside front tire does have have a good contact patch when turning. In fact, when you turn the steering hard & fast, the contact patch narrows immediately. I am estimating about 40-45% contact patch loss. So your outside front tire is going from 11.5" of contact patch ... to 6". Since the rear tires still have a 12.5" contact patch (or close to it) ... the truck goes into an instant push.

      It used to be much easier to take photos and videos of the suspension in action. Here is a shot of the old setup without tall ball joints, which used the stock style S-10 shock with a heavy rate conventional spring that did not allow much travel.

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      d. The inside front tire has a decent contact patch because ... the inside wheel is losing camber as it lifts ... due to the high roll angle ... which is actually helping it. Often guys have optimized the camber for the outside front tire and have the inside tire working poorly. Your situation is the opposite.

      e. You have a soft spring package which is letting the truck suspension travel a lot. That part I like, but you don't have a happy suspension package.

      f. You have a high degree of roll angle from a combination of weight, higher CG and insufficient sway bar size.

      To avoid potential confusion down the road, which might frustrate the turning process I wanted to make a note regarding the front sway bar. In post #5 I included a picture that represents the former and current front sway bars. The former front sway bar in the top of the photo is a stock style S-10 piece, 28mm in diameter. That sway bar was in play in all of the videos provided. The current front sway bar in the bottom of the photo is 33 mm in diameter, but it was only recently installed this winter. I have not tested the current 33 mm front sway bar yet.

      g. You have a slight mismatch in front & rear roll angles. Ideally we want the front roll angle to be .3° to .4° less roll angle than the rear. This creates a balanced handling competition vehicle that is disengaging the inside rear tire more than the inside front tire. Yours is off a little. It is rolling slightly less in the rear than the front ... I'd say around .2° more in the front ... which is about .5°-.6° from ideal. What this does is keeps the inside rear tire too engaged ... and unloads the inside front tire to a higher degree ... contributing to your push condition.

      h. The final ... but BIG issue, is your front shock valving doesn't have enough low-speed rebound. Meaning the front shocks let the inside front suspension roll too much and come up too quick when you step off the brakes. Ideally for AutoX & road courses, you need the shock valving to "tie down" the front end down through the roll through zone. And when the shocks do "let go" and let the front come up, it needs to happen slower. Otherwise it unloads the inside front tire ... adding tot he push condition. You're probably running the shock rebound valving soft for more exit grip, but there are other, better ways of getting exit grip without killing the middle of the corner with a push.

      I will have to try and refer back to my tuning notes for exact numbers (I cannot access them at the moment), but for my quickest lap at the GG autoX, the front shock settings were adjusted just below full stiff for both rebound and low speed compression (somewhere in the range of -6 to -2). In the rear I typically run closer to full soft low speed compression (somewhere in the range of -26 to -20) and somewhere in the middle for rebound (somewhere in the range of -15 to -10). Admittedly, I have struggled with shock tuning in the past. Generally, based on advice that may or may not have been accurate, I ran as much rebound as possible and started at full stiff compression and backed off until my times started to slow down. I really hope to make it to a test and tune event this season because tuning shocks is tricky with just 3-5 runs. In the future I also hope to have better luck using the very easy to follow tuning guide you posted in Lance's thread.

      I posted a link to my quickest lap in post #1, but here is the link again for reference to the above statement regarding shock settings:

      http://youtu.be/R9o9UwR99fE

      Wow! That was a very clear, concise, and alarming snapshot of my suspension that I probably never would have determined on my own.


      So, before we get into changing roll centers, camber, caster, etc ... you need to pick a path for your suspension strategy. There are two good routes to go. And each strategy will need a different roll center and have different needs for optimum geometry.

      #1 is a conventional low front travel/high roll angle set-up. You already have the high roll angle. For this, you would need stiffer front spring rates, reduce the compression travel on dive & keep the soft sway bars. Then you'll need to increase the camber gain & caster in the front geometry to work well with the higher roll angle.

      #2 is a modern high front travel/low roll angle set-up. You already have the high front travel. For this, you would need bigger, meaner, stiffer sway bars, reduce the roll angle from the estimated 3° to around 1.5°. Then you "may" need to increase the camber gain & caster in the front geometry ... but not by much. When you roll the truck 1.5° less ... that's adds 1.5° dynamic camber to the outside tire. You will still want to optimize the camber & caster settings, but it won't need as big of a change as it needs with the high roll angle you have now.

      Each has its pros & cons. If you're not clear on them, I'll be happy to provide insight. But if you're clear, pick a path and let's work on the whole suspension package along with the roll center & front suspension geometry.

      Ron, I borrowed this from your Lateral-g thread, and I think it convinced me a modern high front travel/low roll angle setup is the way to go. If I am understanding it correctly, the major disadvantage you listed for modern high front travel/low roll angle setups (susceptible to dive bomb passes in door-to-door racing) would not really be an issue since I do not race door to door. Are there any other factors specific to my vehicle that I should consider aside from those listed above and below? If not, I think implementing a modern high front travel/low roll setup is my preferred choice, but I am open to input.

      Conventional:
      • Stiff front springs
      • Small, soft sway bars
      • More Roll
      • Less Pitch

      Old School – Let it Roll
      • Moderate to High Roll Angle (3 to 6 degrees)
      • Front suspension doesn’t compress much on corner entry. (3/4” to 1-1/4”)
      • Work the outside tires for grip & work the inside tires less so it will turn.

      Drawbacks:
      • Too much roll angle overworks the outside tires in corners & underworks the inside tires.
      • The tires heat up quicker & go away quicker, providing a better short run set-up.
      • After tires “come in” the car is “knife edgy” to drive.
      • Very line sensitive … drivers say, “can’t drive it just anywhere” … meaning it handles poorly out of its optimum groove.
      • As the track grip increases & the car rolls more … these problems magnify.
      • When it rolls a lot & you brake hard, the inside rear tire has no grip. So to prevent from being loose on entry you must run stiffer front springs.
      • The stiffer front springs make the car tight/pushy in the middle … requiring the driver to brake more and run slower corner speeds.

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

      High Travel:
      • Soft front springs
      • Big, stiff sway bar in front
      • Known as SS/BB … soft spring/big bar … if no bump stop or coil bind is utilized.
      • Same concept used in conjunction with travel stops: Bump Stops or Coil Bind
      • Less Roll
      • More Pitch

      New School – Get the nose on the ground & run the car flatter
      • Roll angle is minimal, controlled primarily by the sway bar in front & stiffer rear suspension. (1 to 1.75 degrees)
      • Front suspension travels a LOT in dive (compress) to put maximum load & grip on front tires. (3” +)
      • Load the outside tires only slightly more than inside corners for optimum 4 tire corner grip.

      Disadvantages:
      • Even when optimized … it still can not be driven as deep on corner entry as a conventional set up.
      • When racing door-to-door in a field of race cars running a mixture of set-ups, the SS/BB set-up is susceptible to dive bomb passes.

      Advantages:
      • Flatter Roll Angle works the tires more evenly.
      • The tires heat up slower & last longer … making a better long run set-up as the tires are “good” way longer.
      • Less line sensitive … drivers say, “I can drive it just anywhere” … meaning any line on the track.
      • As the track grip increases … the advantages show more.
      • The soft spring/high travel front end puts creates maximum grip on front tires for highest cornering speeds.
      • Will produce faster cornering speeds & quicker lap times over conventional set-up, all other things being equal.
      Tyler Gibson

      There's nothing like building up an old automobile from scratch and wiping out one of these Detroit machines... That'll give you a set of emotions that will stay with you... Know what I mean? Those satisfactions are permanent...

    19. #19
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      Don't pay the ransom ... I'm back.

      Hey Tyler,

      I ran the calcs
      in the software and am posting 2 graphs below. One at ride height & the second "dynamic" in dive & roll. For now, I am estimating your dive at 2.75" and your roll at 2.5°. This isn't dead on accurate but close enough to learn, discuss & move forward.


      Ride Height:
      Name:  Tyler Gibson V1 - Ride Height.jpg
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      Dynamic in Dive & Roll:
      Name:  Tyler Gibson V1 - In Dive.jpg
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Size:  125.4 KB



    20. #20
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      Tyler,

      We have a lot to cover & some things to figure out. I'm clear on some things & not on others. I'm going to map out what I see and let's start some discussion to help us both figure it out.

      What I see so far ...
      1.
      You have a lot of stuff right or close to right. I think you're on track with your thoughts and plans.
      2. You have some things not correct ... some are close ... others are not.
      3. You have several things off a little ... enough so that it pushes too easy.
      4. We may ... or may not ... find you have one big thing "off." And that would be what I call dynamic toe, which is a combination of ackerman, static toe out & "bump out" (toe out from bump steer). I can't tell for sure, because we haven't mapped out the steering ... yet. But that spindle has anti-ackerman in it ... so I have concerns.

      5. The two fenderwell camera videos in post #1 ... show me different dynamic tire angles ... which has me a bit perplexed. Are they from the same day? Were there any changes between those runs?

      * The geometry shows plenty of camber, but one of the videos shows the car driving on the outside edge of the outside front tire. Any changes between the date of the video & the date of the geometry capture?


      6. If I understand the order of things ...
      a. You had stiffer springs & the 28mm sway bar, then ...
      b. Went to softer front springs & the same 28mm bar, then ...
      c. You switched to the 33mm bar ... but haven't run it yet.
      ... is this correct ?

      If so, "a" was your "conventional set-up" ... "b" was a high travel & high roll set-up ... and "c" will be somewhat of a high travel/low roll set-up.

      7. Even though the two fenderwell camera videos in post #1 show me different dynamic tire angles ... I still think you have the wrong geometry for that much roll angle. But it sounds like you want to go the high travel/low roll angle route ... so the geometry change will be less.

      Quote Originally Posted by AutoX_a_Truck? View Post
      I typically shoot for about -1 degree of static camber, 0 toe in/out, and according to the FasTrax Adjustable Caster Camber Gauge I can currently register about 8.5-8.6 degrees of caster.
      8. My calcs ... and the software show you have much higher caster than your specs ... and different from side to side. 11.5° on the left & 10.6° on the right. So either your ball joint measurements are off or your caster measuring process is off.


      Quote Originally Posted by AutoX_a_Truck? View Post
      I am also battling a relatively high scrub radius due to my 17x11” wheels with just 4.25” backspacing. Using the method in Lance’s thread, I measured the scrub radius at 4 13/32”
      9. That is a ton for an AutoX vehicle. Where it hurts the most is in the tightest corners ... and especially if you have to give the truck some additional steering input when you're in the corner. You can band aid this some by running an higher/wider entry line ... turning in later & harder ... and apexing later. This will help, but the solution is longer control arms & deeper back spaced front wheels to get that scrub radius down closer to zero.


      10. There are several differences in your geometry settings from side to side. What this does is make the dynamic geometry different on LH turns versus RH turns ... which makes the truck handle differently on LH turns versus RH turns. This is common ... especially in production car ... but never good. My focus is on "how bad is it" and does it merit reworking & TLC'ing the geometry points to correct it.

      Yours is off significantly. Your RC migrates to the left quite a bit (21") on LH turns ... and a ton (184") on right hand turns.

      11. The front roll center is too low one direction (Not 25" .... .25" below ground level) ... and way too high (5"+) the other direction. If all other things were neutral, this would make the front end of the truck roll more on LH turns & less on RH turns. With the numbers I'm seeing, the effect won't be small, so you should be feeling it & seeing it.

      P.S. All things are not neutral, as you have 3" of split in the panhard bar. I'll address that in the next post.

      For a 2.5°-3° high roll angle/Autox set-up I feel around 1.5"± above ground would be closer to optimum. Both directions obviously. For a 1.0°-1.5° low roll angle set-up, you'll want to be around zero (ground level).

      .

      .

      This is hard left hand turn ...
      Name:  Tyler Gibson V1 - In Dive.jpg
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      .

      .

      This is a hard right hand turn ...
      Name:  Tyler Gibson V1 - In Dive - RH Turn.jpg
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      As you can see ... there is some work to do ...



      Quote Originally Posted by AutoX_a_Truck? View Post
      I typically shoot for about -1 degree of static camber, 0 toe in/out
      12. We definitely want to switch to running some toe out, but we need to look at the whole picture. Static toe out helps give the inside tire "some" slip angle ... which makes the tires have more initial turn in grip ... and the steering becomes way more responsive.

      13. We also need to look at what your bump steer does through your realistic travel. Have you bump steered each side individually yet?

      14. The only reason to run dynamic toe (ackerman, static toe-out & "bump out") is to force the inside front tire to achieve the optimum slip angle ... for optimum grip. This is HUGE ... especially for cars running tight road courses & autoX tracks. There is no "one best setting" because it varies with both tire design and suspension strategy.

      Low Front Travel/High Roll Angle suspension set-ups work the inside front tire less ... and require a larger combination of ackerman, toe-out & bump out. High Front Travel/Low Roll Angle suspension set-ups work the inside front tire more ... and require a smaller combination of ackerman, toe-out & bump out. But both need to be tuned until optimum front tire grip is found.

      15. Remember earlier when I said ...
      "You have a slight mismatch in front & rear roll angles. Ideally we want the front roll angle to be .3° to .4° less roll angle than the rear. This creates a balanced handling competition vehicle that is disengaging the inside rear tire more than the inside front tire. Yours is off a little. It is rolling slightly less in the rear than the front ... I'd say around .2° more in the front ... which is about .5°-.6° from ideal."

      What this means is as you work out your spring rate & sway bar rate combo ... you need rear springs & sway bars to achieve about .3°-.4° more rear roll angle than front. As an example, i have a set up that runs the front end at 1.2° & the rear at 1.55° roll angles. This is keep the inside front tire working better & disengage the inside rear tire "to a specific degree" to help the truck turn. Make sense?

      16. Also mentioned earlier ...
      The final ... but BIG issue, is your front shock valving doesn't have enough low-speed rebound. Meaning the front shocks let the inside front suspension roll too much and come up too quick when you step off the brakes. To achieve your AutoX goals, you need front shock valving with both stiffer low speed rebound valving & some degree of rebound valving at zero, before it moves.

      17. As you correct all these things to make the truck turn better ... if nothing is done in the rear, you'll lack forward bite off the corners. Two things that will need to be addressed are shock valving (stiffer low speed rebound) and the height of the IC for "lift & plant" leverage.

      After you read all of this over ... digest it, answer my few questions ... and let's figure out what we need to do make your truck an even better handling machine.

      Next I'll post some info on tuning what we call "Split" in the panhard bar to achieve neutral handling.





      Last edited by Ron Sutton; 03-12-2014 at 05:19 AM.

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