Hey Guys,

I run stock 19" wheels with Pilot Sport Cups on my '07 GT3 and have been searching for the best cold tire pressure for track use (primarily Willow Springs - Big Willow & Streets). Other Porsche owners have suggested different cold pressures ranging from mid 20's to upper 30's psi. I have also been told that 32 psi HOT on all 4 corners is best. Any suggestions?

Appreciate your input!

 

I am speaking in terms of a C5 Z06 on basic street PS2's, but 39 psi HOT was ideal for those. Don't know how helpful that is but if I had to shoot off a guess that'd be it.

 

Depends on track. For example I saw a guy with pressure too low at Texas world speedway (which has a banked oval section to the road course) experience over heating and a blowout and crash due to using too low of pressure. He used the approach that pressure from a diff track would work everywhere. That's never the case. Have to consider weather temp, surface, camber and setup. I would talk with someone at the track with experience but start a little high and then work your way down if you can't get heat into the tires.

 

My car came with the Pirelli P-Zero Corsa's and I found that running with the Porsche recommended cold air pressures worked fine for the track. When those tires wore out, I replaced them with the Michelin Pilot Super Sports and they seem to run best also at the Porsche recommended cold air pressures.
Mr. B

 

To figure out the cold tire pressures, I think you need to determine your targeted hot pressures first and then work backwards. The "best" hot pressures depend on the particular tires, your suspension setup, etc. With a little experience you will learn how much your pressures come up during a track session. Then adjust your cold pressures before you first go out on the track so you hit your hot pressures on the track.

The amount of pressure change from cold to hot also depends on ambient conditions. On a hot, dry day you may see as much as 10 psi change. On a cool rainy day it might be only 3 or 4 psi. On your first run of the morning, you will start out with the lowest cold pressures of the day when air temperatures are at their coolest and you haven't got any heat yet into the tires.

 

Thanks Guys. Appreciate the feedback!

 

Are the GT3 Mfr. suggested temps the same as the C2S? Mine are like 37 and 44 which are WAY above what most people recommend for the track

 

Different. For same tire MPSS. I have 29/33 cold for gt3
33/36 for c4S aim for hot 36 R gt3, 38hot R c4S
Fronts a few psi lower(3)

 

Why is that? I'm guessing a combination of (a) different car weight/expected load and (b) likely use (ie GT3 more likely to be mostly track driven) ?

 

Totally different. My .1RS is 29/33, my .2 Carrera was 37/44. The cars, outside of the shape of the car, could not be more different in suspension, brakes, calibration, tuning...

 

Btw I did add + 5 psi to my tires this past Tuesday at the Ridge track due to rain. Adjusted down after session after rears went to 41 down to 37 hot.

 

I run Sport Cups. For track days I run 34f/36r hot. I generally start 4 pounds front and 5 pounds rears less then adjust 4 laps in. Depending on the quality of the air you're using IE dryness, its usually spot on.
If the pressure goes over 40 you'll notice braking is compromised.
Be prepared though that your tpms alert will go off once you've pitted and allow your tires to cool

 

Start with 28 psi all around and keep it at 37 psi max when hot (the hot psi is key). These tires seem to lose traction above 37 psi. Also, check the tire temperatures as they should be between 180 and 225 F. That's their temperature sweet spot.

 

My rs has cups on it from the factory, Porsche wants 29 and 33 cold , before each run just check and bring them down to that temp before going out again. It works for me . The car stuck great

 

32/35 hot. They tend to fall off in grip after that. Impossible to determine perfect cold temps due to a lot of factors from alignment to driving style to how hard you're driving. Best is to have a buddy with gauge take your pressures after 5 or so hot laps. Good cold target would be about 5psi below hot target to start.