Reducing oversteer at the track. Need some tips!
 

Quick description of the car. Turbo GT86, 290whp, running R compound slick tires on RPF1 17x7.5. Tein Street Flex (-2.5 camber front, around -2 rear, full stiff front, 4 points from full stiff at the rear), AP Racing Sprint kit. Driver (me)... some experience in race cars, but FWD. Not an expert, but not a beginner.

The car feels quite nice entering corners, the nose pitch in, and i dont get much understeer unless i take the corner the wrong way. Problem is mostly at corner exit. Even thou the car doesnt have that much power (290whp) and running slick tires, it tends to loose the rear, even in 3rd gear exits... forget about 2nd gear, gotta be very gentle with the throttle.

Some people recommend bushings, other bars, others wing and difusser... i need a semi cheap solution that i can test and see if it corrects the problem. Any ideas?? THanks!!!!

It is hard to adjust one thing while not affecting a bunch of other things. How is your toe set? I would say play with tire pressures and shock adjustments.

Disconnect the rear bar for one lap. If it feels better at corner exit, you can have a pretty good idea what a stiffer front will feel like.

+1 to tire pressure change first. No investments needed, simplest thing to do to change grip bias.

Do you have any datalogs so we can determine *why* you're oversteering?

I'd say try the tire pressure route as well. It's the cheapest way

+1 on toe given your setup some rear toe-in may give you some much needed stability, measure tire temps to see if your rear camber is appropriate, would not be surprised if more camber in the rear gave you more grip on exit and surpised that a car that aggressive you've got such low camber up front.

What spring rates and what toe settings? Stock bars?

Datalogs would be good, and/or some video.

One other thing...I generally don't recommend running dampers at full stiff. If you feel like you have to for a settled and controlled chassis then you should think about a revalve or different dampers. That said, many just crank them all the way up for track days without thinking about it (which is not a good idea IMO). Generally at the very high settings on low and mid range dampers the car will end up a little compromised and be very sensitive to sudden input changes.

- Andy

Thanks a lot for all the inputs.

I have played with tire pressure. Found out that this tire works best with 24 psi cold and around 28 psi hot. Its quite a stiff tire used for racing championships here in Argentina, and considering our cars are very light, it seems to be a good pressure.

Ive also tested the damping. Running full stiff up front seems nice, the car feels very direct and doesnt have much play, but will try to run a softer setting. In the rear running a softer set up seems the way to go.

Havent tried toe thou. Seems like a good way to go.

Stock bars so far. Will try desconnecting the rear one to see what happens.

You can find videos of the car at the track at my youtube channel. https://www.youtube.com/user/fredxxbr/videos
Be advised, im not a professional driver and not that proficient with RWD. You wont see much oversteer in the videos because i only posted "clean" laps. I always try to reduce oversteer to a very minimum with the gas pedal. So any tips on the driver side would be much appreciated.

thxs!

I'd highly recommend having a friend take tire temps at the pit wall as soon as you come off track. Record the middle, inside, and outside temperatures for each tire, as well as pressures once you've taken tire temps.

A data system could be helpful, but there are other things you should address first. I agree you should try by softening up your dampers simply for the reason that they never work right at full hard.

Please post up your alignment specs. You didn't mention anything about your coilover install, when was the last time you had the car cornerbalanced?

Got it, will try to get meassures in the next track event. Will soften the front suspension a bit before next track.

Aligment was done after coils install, did one track day, and aligment was done again. I suspect they didnt do it right thou. Didnt feel like it had -2.5 camber upfront. 0 toe all around, not that low, max height that the coils allowed due to the bad roads and speedbumps.

Yeah, sounds like your setup needs work before you start spending money on data or new parts.

I'd find a good race shop that will do a corner balance in addition to an alignment, they're almost always sold as separate things unless specified otherwise. A crappy setup could definitely give some of the "quirks" you're experiencing.

Try this for a session. I think you might be pleasantly surprised with the result.

how much toe in would you guys recommend? i have a track day coming and would like to pre-test some settings.