Can somebody explain to me what is wrong with my setup on these Audi R8 type cars? It doesn't matter what I run for a setup these cars have ZERO stability at high speed (300+km/h). I am constantly trying to keep these cars straight down the straights. Once I let off for a corner, the ass end just takes off to one side (totally random). I tried this setup but on my Audi R8 Stage 4 Turbo 1043hp (I don't have the Courage C60 anymore), but these cars are (or should be) very similar. I used a different transmission setup since I couldn't get the gears setup how you state your gears (Auto 1-25 doesn't even allow a 3.382 1st for starters). I just used Auto 20 with your 2.88 final drive yielding a 4.378 1st gear and just went with the gears it gave me. They seem to fit Midfield ok. But the stability issue is really pissing me off. Even on the Test Course oval, the car just jumps around side to side totally out of control. Now I know something isn't right when I can take a C5 Z06 w/700+hp & NOS and exceed 400 km/h and maintain a relatively stable car. This is an Audi R8 meant to exceed 300+km/h and is practically impossible to drive at 300+km/h. I've played with the Limited Slip Decel in both directions, Oversteer in both directions, Brakes Balance in both directions, Suspension settings in both directions, all yeilding no positive outcome. The car is just way to unstable at high speed + decel. Could it be the game or my Logitech steering wheel input signal not working right (that would affect other cars too, but it isn't)? Any help would be gratly appreciated.

looks typicaly like an old chassis.Maybe you have to refresh your chassis (you must "rebuilt" it periodically). See in weight and rigidity tuning section. driving a chassis with a "significant" milleage and needs to be rebuilt is a REAL nightmare.

Even if all the prototypes look quite the same they are actually very different and you can't be sure to get a result using one car setup for another one

OR : you seem to loose rear grip when braking. try to decrease rear brake setting (must be less than front)
weight transfer may also be too strong for a soft front suspension setup combined with a stiff rear. It brings your rear tyres to their grip limit, and a little bump or/and excess of rear brake or / and not beeing perfectly straight (just slightly turning is enough) is just what is needed to make the car instantly spinning. try to soften rear
Or stiffen front (but can induce understeering)
And experiment
Setup is finding a compromise. soft front is good against understeering. my setups are generally based on that. It require to balanced the rear according to this (few rebound, height)

I will try to setup an Audi and post it

Well you were right... it turns out I had to do the chassis refresh. Once I did that she went stable once again. This was the car I used for all the 24 hour races and has nearly 8000km racked up on her, so she was needing a refresh I guess. So it was a $50,000 fix! lol

Thanks!

P.S. after a few laps at Midfield I am doing 54's, a bit more tuning and I should be in the 53's shortly. The hp was dropping fast and I realized the oil was BLACK too, I changed that and went from 980hp to 1080hp, so an extra 100hp should make a difference too.

Well my setup is pretty basic as I haven't begun to tune yet. Therefore my settings are all defaults. I'm using 1080hp, 0 ASM's and 1 TCS, Super Soft tires, Default Suspension, Default LSD, Brakes 8 5, Gears: Auto 24 (2.88 final), No weight Balance, & Max Downforce. Pretty straight forward.. lol

My Best time is now 53.550s

I find it has understeer around the long left turn after the 2nd bridge, but oversteer under braking entering the right turn before that 2nd bridge and while braking through the downhill S turn heading for the slow left hand turn going under the bridge. I lose the ass end while slowing down through the S bend part before that turn. I find if I slow earlier then accelerate for a short period of time through the S, then hard brake into the hard left hander, I tend to prevent the ass end from coming around. But I believe that can be tuned out instead.

So I don't know what to tune for, understeer or oversteer? I got both... lol