Putnam Park this past Friday. Ran with the Prosport Drivers Group. Mostly instructors and guys with 10 years of more experience.

First time I have had the "time and opportunity" to "play" with tire pressure, since it was 6 hours of open lapping.

Normally run 35 psi on the Pilot Sports. Tried lowering 1 psi, then 2 psi.

At minus 2 psi, the tires "thumped" on high g turns. At minus 1 psi, still some "thumping".

Grip was better at both settings but was afraid of overheating and sidewall rollover.

Has anyone else experience such sensitivity with the pilot sports? I would not think that one or two pounds difference would be so apparent.

Pressure settings from anyone else, at a track day, would be appreciated.

Mike

 

Ultra tires are always much more sensitive than run of the mill..........the shape of curves is always more peaky and slip ratios while higher fall off much much more abruptly.
Less forgiving of mistakes.

Unfortunately 35 psi is the standard lab measuring point, really hard to get any data above that other than the max pressure endurance test........I've tried to get Michelin [have a friend at research] to run Pacejka curves at 40 and 44psi no luck yet.

http://www.racer.nl/reference/pacejka.htm
http://www.informs-cs.org/wsc00papers/135.PDF
http://www.millikenresearch.com/rcvd.html

Try 38-40 psi depending on static camber.
What is the tire temp immediately after your runs [must be measure within 60 seconds! Point and click IR temp gun at inner middle outer........take 4 guns/people to do it correctly and fast enough.

 

A tire pyrometer is really the best way to tell correct pressures; that is you look to have equal temps at three points across the tire. If you have too much negative camber, you might have higher temps on the inside edge; but you can still look to have the middle temp equally spaced betwwen outer edge temp and inner edge temp. Personally, I've never used an IR temp guage, my pyrometer has a little pin on the end of the probe that you stick about 1/16" into the tread, and there is plenty of time for one person to take all the readings before the temps change much at all. No need for 4 assistants with 4 gizmos.

Lacking a tire pyrometer, try white shoe polish. Paint a 1.5" square block extending a bit past the edge of the tread surface extending ont the tire sidewall. Then take a few laps. If the polish is removed past the edge of the tread surface, you need higher pressures.

I have run more than a hundred track days (none in my G yet) and have generally found that 38 front/ 36 rear (HOT pressures) is a good starting point for a rwd car.

04 G35s 6MT BS Aero Kit/Nav/Prem
Warning: Objects in Mirror Are Losing!

 

Picked up a pin probe pyrometer today. Going to Putnam Park this weekend.

How should I interprete the temperature variation, as to the inner, middle, and outer measurements?

What changes to tire pressure should I try based on the three measurements.

Being very new at track days, all help and information is much appreciated!

 

For autocross I usually kick my tires up to the 38-40 range. Keeps the edge from rolling under and gives better handling response. Try it out. You may have to run them a little lower though, as they'll heat up more on a track than an autocross setting.

 

Ran at Putnam Park this weekend.

Tried 37 front and 34 rear. Seemed to work fairly good.
Due to scheduling, could not use the pyrometer effectively.

I noticed the thumping was not longer evident. At these pressures, the front and back are showing similar wear patterns, just to the edge of the tread block.

Before lowering the read, the pattern was about 1/4 inch from the edge of the tread block.

It will be interesting when I run an all day open lapping session and get the chance to check the temps.