tire pressure on the track
 

What kind of tire pressure are you guys running for street tires on the track? I just replaced my wheels and tires and my rears look like they were over inflated but I keep 32-34 psi on the street (car calls for 35) and run them at 28 psi cold at the track. Should be adjusting them when the are warm at the track?

It really depends on the tire (and type of racing of course, but I'm assuming DE road course stuff?). With steet-ish tires (up through RS3), my car was pretty comfy at cold pressures in the 28-30-ish range (varies by weather) and coming up to ~37-ish at full temp. With the Conti GT-O slicks I've been setting initial cold pressure in the 20-23-ish range and having them come up to ~30-32. Another guy was running a 370 on Hoosier R6 this past weekend, but he was starting out much higher than me cold, I think 28-30-ish like my street tires? I don't recall how that worked out for him or if he adjusted back down.

Sorry, yes road course ( Sebring) and they were G-Force comp2s. With the air out they have a noticeable dip in the center and don't know why. I just went to RE-11s and much wider and want to get all the traction out of them. I guess I need to start watching the hot temps to see how high they are getting.


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Overinflated. People will swear on their life about one tire pressure or another without any real knowledge of why. It's just what they've set their best times on. Get a tire pyrometer and take 3 temps on each tire at the end of each session. Do this in pit lane. Don't wait til you get back to your paddock space.

In the case of the tire pictured, you would notice the center temp to be considerably higher than the outer temps.

I never look at used tires with the air out, but if it used to have tread in the middle there and now it doesn't (vs the outer edges), then the tires were over-inflated.

The general idea is you guess a good temperature and then measure after each session to dial it in.

In an ideal world, you pull into the hot pit during a hot lap with the tires fully warmed up and have a friend check the tires with a pyrometer as fast as possible. You want 3x readings on each tire (left, center, right of the tread face). In a less than ideal world, you can wait till you come in from the session and hit those 3 areas on the surface with an IR thermometer. If the pressure's right, you should be seeing approximately even temps. If the center's hotter they're overinflated, if the center's colder they're underinflated. If there's a gradient from left to right on the temps, your alignment isn't right (e.g. needs more front camber if the front inner edge is colder).

You can also generally tell just by looking closely at the tire after a session and noting how the rubber is wearing/melting (hopefully evenly). Another similar method is to mark over the shoulder corner with some chalk (like an inch of tread and an inch of the sidewall), and see where the chalk gets scraped off. If it's set right, the edge of the chalk should end up at the edge of the tread surface...

Thanks for the ideas.

I run RE11s as well and start the fronts at 31 to 32 and the rears 30 to 31. I have tried a couple psi lower but find if i start as stated above times are better and the car feels better.

What size RE11s are you running? Are those temps on cold tires?

Cold Temps: 25 psi
HOT Temps: 38 psi

I mean hot like... it's nearly too hot to check the tire pressure because of the heat coming off the brakes.

I find 10 psi of tire pressure change to be fairly consistent.

Recommendation: start 5lbs below where you want your tires to be. Then adjust PSI for sidewall wear marks. <-- ask if you don't know what that is

Sorry...that is where i start cold. Running 265/35/19 & 305/30/19

Sharing cold pressures will be pretty useless as aggressiveness, surface, and other variables change from one driver to the next.

With RE-11s I like hot pressures around 36 front 33 rear. With plenty of camber and roll stiffness you can have the ffronts a little lower.