SammyTownPfan

Hey Guys - I'm still relatively new around here, although I read several times a week. I introduced myself in April (post and pics here: https://rennlist.com/forums/showthre...ferrerid=51866)

Since then, I've enjoyed putting 3k miles on my '04 C4S and am now at 18k miles...it's an amazing car.

Tomorrow, I'll do my first DE event with it and I'm getting conflicting advice on tire pressures (I've searched )

Here on Rennlist I read the following in the 996 FAQ:

"Porsche's factory "recommended" pressures for the 996 are 36/44 front rear [Ed: My handbook says 36/36 for the C2 with 17" wheels], which are way too high, IMNSHO. I lowered mine to 31/33 cold, and the car works great that way. I'm not getting much rollover at all (just a smidgen - certainly nothing to be concerned about), and I can't imagine many people driving harder at a track event than I do. The Boxster Board members who went for rides with me can report on how well the car worked at those pressures. Also, a friend of mine at the event finally lowered the pressures on his C4S from the factory recommended 36/44 (I've been telling him to do it for some time now), and he watched his times drop by about a second, I believe"

But, the driving school I'll be with (Proformance at Pacific Raceways) included the following in their briefing packet:

"Tires…good condition, adequate tread depth, and no “plug repair” to punctures. Tires should be over-inflated by approximately 5-10psi over normal specifications when cold"

So, which is it?? I have 18" wheels that call for 36/44 (front/rear) cold pressures. Do I move it up or down (and by how much)?

I'm running Pilot Sports on the car.

Thanks much for any advice!

hwk72

I did experiment quite a bit with the tire pressure on my car (C2 Cab) during my last 2 DE events and feel that the mentioned pressure of 31/33 cold is a good track tire pressure for the 996. I run approx. this pressure. You need to consider that after a 20-30min session the hot pressure is most probably above 40psi all around, so I think going even above the factory recommended pressure is dangerous as the factory pressure is meant for street driving whereas on the track you push the car harder which increases the pressure even more. Above is meant for street tires; I have BS Pole Position S02 225F/275R on 18''. Again for street tires, I think it's important to stay at least 2psi higher on the rears.

pat056

I'll give you my 2 cents worth. It comes from 5 years of DE's and instruction and 3 years of racing Porsches. When I did DE's on street tires, I tried to achieve 40 psi HOT on all four tires. I would think your 31/33 cold would work. Get a pyrometer and get the optomal temperature across the tire for that compound. I'm not a compound expert, but am sure someone more knowledgeable than me will respond. Until then, target 40 psi hot off the track.

Bob Rouleau

Agree target 38-40 lbs hot. Start about 6-7 lbs below the target cold. Be prepared to bleed down to target hot pressure. measure pressure as soon as you get into the pits after every run. If you let hot pressures go above 40 lbs the car will feel unstable, especially in the rear.

Regards,

2something

996 C2 with Michelins Pilot sports, I start with 31/35 for a normal track day.

However on a car limits handling day we were practising taking one corner of an airfield at up to 90mph with the odd spin or two. After a couple of goes the instructor checked the tyrewalls, noticed some damage and got me to pump them all up to 48. The max should be listed on the tyres and was 51 for the contis I had at the time. I started the day with 33/41).

I think it depends a lot on what you're actually going to do on the DE, maybe just take a pump along and ask the guys running it for advice.

SammyTownPfan

Guys - thanks for input and advice. It was certainly my intuition that you'd want to start with lower than stock pressure levels. I'll aim for 40 hot as is suggested.

Also, the "curriculum" is as follows:

Slalom course, high aim vision and advanced car control
Threshold braking – ABS experience – ABS avoidance maneuver
Emergency lane change – crash avoidance
High speed controlled road course lapping (three 20 minute sessions) – instructor present at all times

Appreciate the quick replys and input. Thanks.