Tire pressure for track day

eville_stu · Apr 8, 2009, 04:55 PM

I'm doing a trackday next week, I've got a totally stock GSR. What cold pressure should I start the day with? Just looking for a starting point... I'll adjust from there as needed.

MrBonus · Apr 8, 2009, 05:07 PM

I found the OEM Yokos liked around 30 PSI cold. Regardless from 30 - 34, I found that they heat up extremely quickly and start to howl like a banshee, losing grip the entire way. I wanted to go lower but figured that would only accelerate their loss of grip.

Clipse3GT · Apr 8, 2009, 05:26 PM

I run 32 psi. If you good too low, they will heat up quickly, and the tire will roll on the side wall too much. Slightly higher and they heatup a bit less, roll less, and are a bit more stable. But you should experiment what works best for you.

trackjunkie01 · Apr 8, 2009, 06:53 PM

For street tires set them around 36-38psi and leave them. The tires won't wear as badly and give you a stiffer side wall. Track tires are much lower.

Hiboost · Apr 8, 2009, 11:31 PM

I would suggest starting at 32 psi cold, maybe as low as 30 psi. On the street I run 35 psi all around and that heats up a couple PSI at most but at the track you can jump 4-5 psi after some hot laps which puts you too high. In addition once you run the track you will find that some tires might be higher depending on if the course has more right or left turns.

It is true for street driving you want to set the tires cold since in most cases you will evenly heat up the tires.

On the track, the hot tire pressure is what you want to balance out so I would recommend 32 psi cold and then once you get done with your first session adjust them down to 34-36 psi all around. Lean towards the lower pressure range if the tires aren't rolling that bad, keep them higher if they are. If you want a little more oversteer keep the rears slightly higher than the fronts, if you want more understeer then keep the fronts higher. Much of it is personal preference and can be effected by suspension mods like rear sway bars and springs/coilovers as well.

eville_stu · Apr 9, 2009, 12:41 AM

I'll let you know how it goes... Laguna Seca on Monday

dcpatters · Apr 10, 2009, 05:15 PM

I came across this on the Tirerack website

Adjustments.........................Decrease Understeer..............................Decrease Oversteer
Front Tire Pressure......................Higher.............. ....................................Lower
Rear Tire Pressure.......................Lower.............. ....................................Higher

Is it different for an AWD car?

Hiboost · Apr 10, 2009, 09:56 PM

Well the Tirerack chart is right but it's really the ratio of front to rear traction that determines if a car oversteers or understeers. Also factor in driving style, temperatures, and what adjustments were made to the car to handle the way it does all can effect how a car handles under various conditions. This is from reading various articles online and practical experience.

All tires have an optimum pressure (and operating temperature) for maximum grip and keeping them at an even temperature across the contact patch is usually the aim. Usually grip increases as you lower the tire pressure until a point where the sidewall becomes so soft that it rolls over in turns. Exessive heat from a sidewall flexing too much will make a tire more slippery. An exception to this would be straight line drag racing, then going somewhat lower than optimum can still increase traction assuming you don't need to turn the car.

So if fronts are Optimal, and rear are set for Optimal +4 PSI, you will run cooler than optimal in the rear with more sidewall stiffness, slightly less contact patch, and more Responsiveness. Having Less Traction in the rear of the car in relation to the front results in more oversteer. You could also have the front at optimal and rears Optimal -4 PSI in which case you would flex the sidewalls more and increase heat to where they would become more slippery with less responsiveness.

If you were Optimal -4 PSI in the front, and rear at optimal, this would induce understeer compared to previous example. Now you have less traction up front due to overheating tires rolling over on the sidewalls and getting slippery where as the rears are still at the optimal pressure compared to the front. Go the other way and have Optimal +4 PSI front with rear at optimal and you would see more responsiveness from the front tires but less traction, slightly less contact patch, increases sidewall stiffness.

Both examples would assume these are hot running temps and you are out on a track where you need make turns.

A better way to do a chart would be:

Adjustments......... Decrease Understeer..................... Decrease Oversteer
Adjustments........... Increase Oversteer..................... Increase Understeer
Front ....................... More Traction ................................. Less Traction
Rear ........................ Less Traction ................................. More Traction

You can check this link out, mainly shows how all the different mods effect how the car handles, and how going too far in either direction will reduce traction at that end of the car.

http://www.lfsforum.net/showthread.php?p=1074405

and

http://www.racelinecentral.com/RacingSetupGuide.html (More for a circle track setup but if you filter out that part it's an interesting read)

Using the tire pressures to reduce traction at one of the car or another is basically a band aid since now you are sacrificing some of your total available traction from your tires limited contact patch in an effort to control the cars behaviour. The best option is to have front AND rear tires at optimum pressures for the temperatures you are using them at and tune the car's handling characteristics with suspension adjustments to where you want it to be.

dcpatters · Apr 10, 2009, 10:12 PM

Cheers for the explaining in greater detail. Much appreciated

Hiboost · Apr 10, 2009, 11:14 PM

I also stumbled on this online article about road racing which has multiple articles that you can navigate through. This section has a "Handling Tuning Table" which details the extremes of certain mods and what to avoid, including tire pressures being too high or low.

http://www.turnfast.com/tech_handlin...ng_tuningtable

chincster · Apr 12, 2009, 08:57 PM

i run 34 cold and try to keep at 36-38 hot while at the track. if you're running stock alignment, you will need adjust keep these pressures consistent as there will be significant outer tire wear from under-inflation. that's my experience though.

cfdfireman1 · Apr 12, 2009, 09:21 PM

Cold pressure doesn't mean a damn thing. How cold is cold???? Get one of these and learn how to use it. http://www.hrpworld.com/index.cfm?tp...action=product

omarv6 · Oct 21, 2009, 11:50 PM

i am running 235/40/18 TOYO R888 i have it on 30psi Hot when the Temp is its 35 Deg.
you just need to play with it till u find the sweet spot .

goofygrin · Oct 22, 2009, 07:13 AM

lol bumping the 6+ month old thread.

kuvesh · Oct 22, 2009, 09:55 PM

i now run 36 in the front and 34 in the rear cold.

the first track day i had with my evo i ran lower pressure (around 32/30) and totally messed up the shoulder / side wall of my advan sport tire (don't flame me, yes i know its not a track tire but it came with the car).

in fact, some "experts" told me the right pressure is the oem settings when the tire is cold. maybe when they heat up you can deflat a little but try to keep around the oem.

just my 2 cents...