996TWINS

After seeing post #8 I forgot what the topic is about

911Königin

I take it that you don't frequent the IHI thread

aj986s

That used to be a good way to measure the resulting effects of tire pressures. And while it can still be useful today, modern low profile tires don't seem to roll over as much/easily as taller tires of days gone by. You can still use chalk to validate, but it seems to require a much larger change in pressure nowadays to cause a significant change in the chalk line. IMHO, better to find your optimum range, and then use a guage to periodically check the pressures (most tires nowadays seem to operate somewhere between 32 & 36 cold; 34 & 40 hot).

disasterman

I had made a comment on another thread you had started about purchasing tires at the track about recording data.

Knowing tire pressures and adjusting and comparing must be done in relation to ambiant air temperature. While I agree that it's not important to record tire temperature, you cannot ignore air temperature.

Simple Kestral brand guages (miniature weather station) will provide you a with air temp, relative humidity, wind speed etc.

Your concern should be starting tire pressure and immediate off track pressure. Initial pressure settings will change dependant on air temperature and type of tire. Pressures coming off the track (hot) should be the optimum max pressure for that tire. As the tire heats the pressure increases.

aj986s

As long as you've started out somewhere close to 32 PSI cold, you will be fine for your first couple of sessions. Talk to your instructor beforehand about your interest in trying to get the tire pressures setup properly. If the event isn't overly busy, you may get an opportunity to have your instructor help you quickly check the pressures as soon as you come off the track. But remember that debriefs with your instructor after each session will be important, so try to avoid compromising that time.

But, bottom line.....have fun!

mrbill_fl

also keep in mind parking the car in the sun.
easily 2 lbs different on the tires in the sun vs the shaded sides.

IMO, its the hot temps you really want to look at. and work back for the next session.

also the differential front to back. If I want loose (autox) I make that more than 4# different.

but I'm not sure how much any of this really impacts a street tire. they just seem to work in a much wider range.