What Hot Tire Pressure?

[gbgracer]

I have a set of Michelin Super Sports in 225/45/17 on my FRS and have really hurt the sidewalls badly doing HPDE's. To remedy it I will upgrade the sway bars in an attempt to reduce body roll.

However, I suspect part of the problem is too much tire rollover. I was hitting 38-40 psi hot, is that not enough pressure to prevent rollover?

What pressure would be a good starting point?

Thanks!

[TemeCal]

I personally wouldn't do anything with your sway bars. I'd work on getting more camber first. I can't tell you on the tire pressure, but I'd think you're on the high end.

Do you have camber bolts installed, or are you running everything stock? Camber bolts are a cheap solution (less than $20) and will give you ~0.5deg more negative camber.

[gbgracer]

When this happened i already had RCE yellow springs, Whiteline top hats and camber bolts which put the neg camb at 2.3F and 2.1R

[orthojoe]

Your problem is not enough negative camber (although -2.3 seems like a decent amount). Maybe it's time to get camber plates? Every tire and driving style is different, but most of the time I aim for 38-40psi hot.

[7thgear]

problem could also be over-driving

drive within the car's limits, if you're understeering into every turn then consider using the brakes more.

[7thgear]

also, if you want a real answer as to what pressures to set the car at for that tire is to measure the temperature after runs and record your settings

then cross-reference this with available literature to figure out what the proper setting is for your tire/car/track.



also, a 2 degree spread is quite a discreprency, i would "aim" for much smaller brackets.

and feel free to experiment, start off high, go out, come off, let some air out, then compare findings.

[wparsons]

Some people are finding -3* up front works better, especially with tires with softer sidewalls.

I'd agree with what 7thgear said, if it's pushing hard every turn you'll likely be faster by entering turns slightly slower.

[UncleFester]

I run the same tire in a 245. 36F 34R and I have no roll over issues. I'd say it's your driving style.

[gbgracer]

Thanks for the tips everyone. I'm also going to be trying a larger 20mm front bar this Sun so I'll see if that helps as well.

[Dezoris]

Originally Posted by gbgracer

Thanks for the tips everyone. I'm also going to be trying a larger 20mm front bar this Sun so I'll see if that helps as well.

Are you coming from a FWD car before this?

[Captain Snooze]

Originally Posted by gbgracer

I'm also going to be trying a larger 20mm front bar this Sun so I'll see if that helps as well.

Doing that will probably increase under steer which won't help with your problem.

[s2d4]

.

[gbgracer]

Dezoris/Captain Snooze,

I race SRF with the SCCA. SRF is an open cockpit mid engine spec series. I have tracked a track modded Subaru STI(my former car)quite a bit as well though. So I do drive the car hard and have extensive competitive experience...

My concern is that the larger front bar would increase understeer as well as that would normally be the case. However, so little of the front tires contact patch is used right now I'm hoping that the increased roll stiffness will keep more of the contact patch on the ground and offset the normal effect of a bigger front bar.

Tomorrow I'll find out though...

[CSG Mike]

I understand you have experience, but this is not the same as an open cockpit racecar, and a STI.

The solution to your problem, similar to the STI, is more camber. We were chunking tires when we attempted to run with a bone stock setup.

Reducing roll will help, but not as much as getting a proper alignment. Have you gotten any pyrometer readings? That'll confirm what everyone else, including myself, is telling you.

Just trying to save you a headache.