DE Tire Pressures

[CarreraS]

OK, every time I ask this question at the track I get a different answer.  So, now is the chance to get 30 different answers on the forum! 

Scenario: 997s...19 inch wheels with Pirelli stock tires...cold inflation recommended at 37/44

At the most recent T-bolt event a couple of weeks ago, I set the pressures at 32/37 cold.  After each session, I was consistently at 37/41 hot.  Car felt great except through the octopus and that was definitely more my fault than the tire settings.  I did notice some sidewall wear on the driver's side front.

Am I in the right ballpark with where I'm setting my pressures when cold?

Also, I'm doing the SCH T-bolt event on Saturday with expected temperatures to be significantly lower than a couple of weeks ago.  Do I go with a cold setting closer to the recommended settings?

All you fast guys, please throw in your two cents.  Thanks!!

 

 

 

 

[Larry Herman]

The right way to find the optimum tire pressure?  With a pyrometer and a data logger.  Otherwise you are just going off of feel and tire wear; both are notoriously inaccurate unless you can feel minute differences in the car's handling like a pro can.

That said, you can try upping the hot pressures in 2 lb increments until the tires feel greasy, and then drop back.

IMHO 37 sounds low for the fronts, should be up around 40 at least.  And yes, if it is colder out, you need to start with higher pressures.

[CarreraS]

OK...my next stupid question...sorry...after I get the pyrometer what is the optimum temperature that I should be looking for?

I apologize for my ignorance on this subject.
Thanks!

[Larry Herman]

Not a stupid question at all.  Basically, you need someone to take 3 temps (outside, middle & inner) across the tread of each tire, preferably right in the pits when you come in off of a hot lap (not after the cool down).  It is the difference between the readings that is the key.

Tire temps 101 - If the middle is cooler than the outside your pressures are too low, if it is hotter then your pressures are too high. If the outside is more than 20 degrees hotter than the inside you need more negative camber.  The ideal would be for the outside & middle to be around the same temp, and the inside to be no more than 10 degrees cooler.

[CarreraS]

Thanks Larry!! That's very helpful!

[JimWirt]

your car has dialed in understeer from the factory to make it safer to drive for the average joe. If you want it to turn and corner better you will have to get more camber. The only way you will be able to get it to turn is by lifting alittle and trail braking which you are not ready to do. So my advise is to live with it until you have a few more events under your  belt.  Just try not to muscle the car around to much. Your  car is so awsome with that pasm. It probably wouldn't let you spin even if you tried to spin it. But that is what also makes it hard to get it to turn. My m3 is the same way.