Total Lateral Load Transfer Distribution

[Sleeper68]

Been awhile since my last post. I figured I would document my tuning progression to help others with the same type of issues I have been having.

The event after the one above was in Georgia at a CRSCCA event. Tight but fun course. Prior to the event I made a change to the car to reduce understeer (increase oversteer) by stiffening the rear via the use of rod end turnbuckles anti roll bar endlinks as opposed to the polyurethane bushed endlinks I had been using. In addition to this I increased the camber angle to -2.2° from -1.5°. Toe was set at 1/8" out (total toe). Car did great. helped alot with the understeer but still had slight turn in understeer. Ended up 5th PAX with a big heavy car. Link to video below:

https://youtu.be/g3PCvbclDA0

After the CRSCCA event I went to an event pretty far away from home (5hrs). That was the first time the car was on a trailer in 6 years. Car made it two runs before blowing the muncie trans. Good thing it was trailered. Next event not until 2021....

Event #1 in 2021 was a local ETRSCCA event at Bristol. Very cold, had alot of trouble getting the rivals up to temperature. Highs in the mid 40s when I was running. Car did decent but had to baby it due to the cold tires. Placed 2nd in CAMT. Link to video below.

https://youtu.be/3KSN1t5oynk



Event #2 in 2021 was an autocross guys event. Tighter course. Car did well but still had some understeering issues. Mid corner and corner entry. No change from previous setup.

https://youtu.be/ZZLDgcWE1Io

Event #3 in 2021 was at Bristol again, ETRSCCA. Just before the event I made a change. Moved the battery to the passenger side of the trunk, removed the front bumper, and lowered the front RC about 0.5". RC movement was achieved by changing the upper ball joint pin to a 0.5" tall version from a 0.9" tall version. Bumpsteer was corrected after the change. Alignment set at -2.0° camber, +6.5° castor, 1/8" toe out. Won CAMT by 0.57sec. 14th PAX.

https://youtu.be/NAzwijUgC04

Event #4 was a very tight course at Smokies Stadium with ETRSCCA this past weekend. Prior to the event I installed some double adjustable rear dampers from Varishock I had. The dampers I had been using previously were also varishocks but they were non-adjustable. The doubles are capable of much more damping force than the non adjustable versions. I set the bump damping as close to the non adjustable shocks as I could. For rebound I went approx. 2 clicks stiffer as far as I could tell. Did some street slalom testing and set the rear rebound where the turn-in understeer was reduced to a minimum without making the car overly loose. Placed 1st in CAMT by 0.082s and 20th PAX. My driving was pretty sloppy and on my fastest run I messed up the hairpin badly. I think the shocks improved the braking initial "bite" of the car alot but I was timid on the brakes as to not lockup. Need to drive the car harder with more conviction, trust it more, and be more smooth. This should help me keep a better and more consistent line and stay tighter to cones that need staying tight to. I also need to brake harder. Video below.

https://youtu.be/haloDI0p5Bs

Please feel free to critique driving and car behavior. Additionally I am open to any and all suggestions.

Thank you

[Sleeper68]

More updates. After Event #4 I found that the bushings in the rear dampers were virtually destroyed. This seemed to happen because the the shock was initially mounted "cantilever style" which put the bushing in a big bind. I did not run the car like this but only mocked it up. Ended up making clevis mounts to keep the bushing from binding but the bushings were old and the damage was done. Got new bushings after the event. One was beaten out of the shock and the other was almost gone.

Event #5 was also an SCCA event @ Bristol Motor Speedway. Very fast course, placed 2nd in CAMT, 18th PAX, 52.872s Car felt alot better here but still pushes. I found that I can get the car to rotate is some situations with throttle, but in others it wants to push.

https://www.youtube.com/watch?v=W4fypAEUd48

Event #6: SCCA National Champ Tour @ Bristol. Day 1 was rough. Car pushed alot, could not get heat in the tires in 3 runs, and my driving sucked. I was way too timid. 7th out of 11 in CAMT, 208th PAX, 59.601s.

https://www.youtube.com/watch?v=3MTUs7z9aJA

Day 2 I did alot better but stayed in 7th of 11 due to the addition of time from both days. I bumped up the rear tire pressure 2psi and stiffened rear rebound 2 clicks. This reduced the grip in the rear (not what I wanted to do but was forced to at the time) but made the car alot easier to drive. It turned in alot better. Additionally I drove the car a lot harder and used the throttle more.

https://www.youtube.com/watch?v=p9eYX6oQzeA

At the latest event I worked on my driving. No setup changes. 1st in CAMT, 12th PAX, 17th RAW.

https://www.youtube.com/watch?v=6rFlDfnxd40

The next event is this coming weekned. I did some thinking over the past few weeks and came up with an idea, that alot of others have talked about, to use jounce bumpers (aka bump stops) to tune the front end stiffness easily since I am on leaf springs and regular, factory style front springs. I purchased an array of bumpers of varying stiffnesses to test out.

The first thing I am going to try it to remove the front jounce bumpers completely. Looking at pictures of the car mid corner it became clear that the car was in some way pivoting on the outside front tire to some degree. My theory is that this is due in part to the jounce bumper being loaded, not allowing the front end to articulate as much as I would like and thus not taking advantage of the "improved" camber curve as described in previous posts. The distance between the bumper and the bumper "landing" pad is about 1/2" - 3/4" at ride height. Not alot of movement allowed. You can see this somewhat in the attached picture. Outside front tire appears heavily loaded and camber relative to ground plane is poor - possibly even positive. Alignment is -2.0° Camber +6.5° Castor 1/8" total toe out. Tire pressures 33.5psig front 33.0psig rear on 275/35R18 BFG Rival S 1.5s.