Hi all, though the Covid period threw me for a loop and kept me off track for a few years, I hit it a couple weekends ago for the first time in 3 years at Putnam Park in Indiana. Great experience with SCCA Time Trials, excellent run group in Intermediate, may have had to wait one corner for a point by all weekend through 10 sessions. For reference my best time was a 1:16.494, second to a 2017 GT350 in my class.

That said, either me or the car provided some very unwanted behavior.

Having read dozens of threads on the topic (without finding anything definitive for my specific question), here are the stats:
245/315 A052's
RUF springs (identical to H&R Sports so I think 360/820 F/R and about a 1.25" drop)
Bilstein sport front/Koni yellow rear (full stiff- full soft was a nightmare)
Rear adjustable bar set to full soft
Stock front bar
Alignment (all identical L/R- I have a good shop!):
-2.5*/-1.5* camber F/R
+.04*/+.20* toe F/R (+ being toe in)

That said, here's what's happening:
Corner exit is amazing. I can plant it at any point around the apex and it'll track out perfectly. No instability whatsoever Braking is stable though I was on Textar pads so I took it pretty easy on the brakes (Hawk sent me the wrong front pads so I had to stick with stock).

Corner entry, the car turns in great but then loses the rear. This happens on level corners, decreasing elevation, and increasing elevation. It doesn't matter what the track is doing, if I turn in at a speed that the car feels it can handle, the rear end comes free and is pretty much unrecoverable unless I over-slow for entry and CREEP in steering input (this is a me thing, I'm an autocrosser so slowing my hands down is a definite area of focus for me on track).
Mid corner, again regardless of track situation, the rear wants to come around. This happens on trailing or constant throttle. Only under hard accel does the rear stabilize.

With running in Sport class, I'm not allowed to change arms or bushing material, and I'll know tomorrow about alignment slippage but given the behavior was constant from the first session to the last and the car was aligned 24 hrs prior to going on track, I don't THINK that's gonna be our culprit.

Is there anything I can do to try to make this thing even somewhat driveable? I'm losing probably 1+ seconds per lap due to having to overslow for corners and even transitions (I know, I need data acquisition).

Thanks!

 

Should check rear alignment to make sure something has not shifted. This sounds extreme.

BUT
Am I reading correctly that you have Bilstein's up front and Koni in rear? Why two different shocks? Never liked cross matching. Whatever.

Sure, hard acceleration will shift the weight back and plant the rear.
But while full soft on rear might have seemed a nightmare, full stiff in rear could be the culprit. You already have a lot more rear spring than front.


Try going softer on rear shocks albeit not full soft.

BTW - Most shocks don't like being set on dial to full extreme setting. Make sure you are in a click and not just dialed as far as the **** will go......