Any of you racers help me out. I recently bought a 968 ClubSport that came with a spare set of wheels fitted with new Pirelli PZero slicks. I'm planning on using them next week at Brands Hatch and wondered whether tyre pressures on slicks should be the same as normal road tyres. Any advice would be much appreciated.

<img src="graemlins/icon107.gif" border="0" alt="[icon107]" />

 

I would go somewhat lower than street - I was running a 993 with P-Zero Cs and ran COLD PRESSURES of 28psi front and 30psi rear - this seemed to work out well.

For a 968 you might want to start out at 30psi all round COLD and aim for 42 psi or so HOT

 

Ooooooooops mis-read your post - my advice was for P-Zero Cs, not P-Zero slicks (if they are different), although the advice on low 40s psi HOT is pretty universal.

 

[quote]Originally posted by Chris in Detroit:
<strong>Ooooooooops mis-read your post - my advice was for P-Zero Cs, not P-Zero slicks (if they are different), although the advice on low 40s psi HOT is pretty universal.</strong><hr></blockquote>


...pretty universal except for some R-compound tires, and especially not for slicks. I can't remember the exact numbers, but I think the recommended cold pressures are 25 front / 23 rear, and hot are around 32.

 

DJ - I did some more digging - seems that specs vary very widely e.g.

<a href="http://www.tirerack.com/tires/hoosier/hoosier_tips.htm" target="_blank">Tire Rack - Hoosiers</a> recommends low 40s hot unless your car is very light

<a href="http://www.tirerack.com/tires/bfg/bf_careandfeeding_gforce.htm" target="_blank">Tire Rack - BFG-T/A R1s</a> recommends 40-45psi hot

<a href="http://www.tirerack.com/tires/kumho/ku_v700_care.htm" target="_blank">Tire Rack - Kumho V700</a> recommends 35-40psi hot

BUT, then I found

<a href="http://www.visionmotorsports.com/Tires.html" target="_blank">Pirelli Tech Specs</a> which as you said, recommend hot around 32psi

SO, very much depends which slick tire you have ......

 

[quote]Originally posted by Chris in Detroit:
<strong>
<a href="http://www.visionmotorsports.com/Tires.html" target="_blank">Pirelli Tech Specs</a> which as you said, recommend hot around 32psi

SO, very much depends which slick tire you have ......</strong><hr></blockquote>

All good info, Chris, but the pressure specs on Dwain's site are most likely for 944's, as Vision is mostly a 944 race shop. Still, the numbers would be in the same ball park.

Also, in this group of tires, only the Pirelli is considered a slick. The others are DOT-rated R-compound tires. Big difference.... about 4 seconds a lap.

 

Chris and DJ, many thanks for your assistance on this. My tyres are indeed Pirelli slicks and thanks to your help I now know what pressures to put in. I had a feeling that they should be lower than normal so I am glad I checked first.

 

Steve:

DJ’s recommendation is spot on. I have run numerous sets of Pirelli slicks on a GT3-Cup car and our fastest lap times were achieved at 32-33 PSI hot. If you are using air rather than nitrogen then you might want to start with a lower initial pressure like 25 PSI or even 24 PSI if it is hot day. It takes the Pirelli slicks at least two laps to generate enough heat to really stick, so be careful.

Hank

 

Hank

Thanks for the advice on warm up times. All I need now is for the sun to shine.

Regards

 

[quote]Originally posted by Hank Cohn:
<strong>Steve:

DJ’s recommendation is spot on. I have run numerous sets of Pirelli slicks on a GT3-Cup car and our fastest lap times were achieved at 32-33 PSI hot. If you are using air rather than nitrogen then you might want to start with a lower initial pressure like 25 PSI or even 24 PSI if it is hot day. It takes the Pirelli slicks at least two laps to generate enough heat to really stick, so be careful.

Hank</strong><hr></blockquote>

Someone, PLEASE ask Hank how he knows about the 2 laps rule for Pirellis !