4pipes

What starting tire pressure did you use? The supplement calls for 41psi all around-HOT.

I'm assuming the OEM tires.

If you start at 35psi(door value), did you end up way higher than 41psi?

I know ambient temperature can vary, I'm just trying to estimate my starting pressures.

2012YellowBoss

I found when the tires heat up on street runs it adds about 4 PSI so I started at 37. I did have to take a little out after the first run since they heated more then normal street use. 35 may be a little low to start with in case they do heat enough where you are at, I think 37 is a good starting point.

4pipes

Thanks, Scott, that's what I wanted to know. The ambient temp will be in the high 80's Friday so 35psi may be a great starting point.

CDGun

Fill with nitrogen and they will remain stable with temprature changes

4pipes

I know, but too much trouble.

P0 Corsa

Actually a tire filled with pure Nitrogen or air (which is 78% nitrogen, 21% oxygen) will behave the same relative to pressure and temperatue.

Both these gases (one an elemental gas, the other a mixture) obey the "ideal gas law" which gives the relation Pv = nRT.
http://en.wikipedia.org/wiki/Ideal_gas

Thus (at a constant volume, like the chamber of a tire) if the "T" temperature on the right side of the equation goes up, the "P" pressure on the left side goes up to maintain formula equality.

4pipes

I believe the tire volume changes with pressure.

Dig-It Racing

I started at recommended cold 35 psi and ended up at 40-41 psi after each session. I didn't mess with the tires all weekend other than checking the pressure after each run. The weather was sunny and upper 80's at VIR.

Bueller

There are a few variables that determine cold pressures for the track, namely total driver experience, driver experience at a particular track, ambient air temperature, etc. Novices that learn quickly tend to "chase" tire temps as their speed increases and the tire working harder with each successive run.

I do not have track experience with the Boss, but Dig-It's suggestion looks like a great place to start.

cloud9

I started at 35psi with the Nittos and found I wore the centers getting to 42-44 psi hot. I dropped to 33, then finally settled at 32 psi cold my last day on them and that seemed to be a better starting point. Ended at 41 psi hot on a cold day that day (mid-60s). Not sure on stock Pirellis though since I haven't driven them on track.

4pipes

Just re-read the supplement, the answer was right there. Suggests starting as low as -4psi depending on ambient and track temps, driving style. Since I'm going to take it easy for a couple of sessions, I think I'll start at -2psi or 33 all around.