Stuttgart951

+1

Allen

I run: front = 36 psi rear = 40 psi

Ed Burdell

Emphasis on the word "good" alignment. I've had it checked twice now and have been told by two shops that it's a combination of the widebody and the lowered suspension that leads to accelerated tire wear relative to other 993's. Not quite sure I'm buying that yet.

speedbump2

Maybe you're at the adjustment limit on the rear lower control arms.
Are there any aftermarket control arms available for your car?

--Chuck--

Slow Guy

I didn't look at the 993 door sticker today but I know on my other 3 cars there are 2 pressure readings on the stickers. One for moderate load (couple psgrs. and little luggage) and one for full psgrs. and full luggage.

Canyon56

Me, too.

speedbump2

Not that there's any corrolation, but my VW has the same width 18" tires all around, and has the same 36/44 psi (cold) recommended on the door sticker.
With the way the car is weighted, I've found 38 psi (cold) all around to be optimal for the street, and I knock them down to 35 psi (cold) all around at the track.
But that's the same tire size all around. You guys would probably benefit with a little more psi in the rear than the front, but 44 psi seems a little excessive.

--Chuck--

PNogC2S

This is has been an interesting thread. Now I'm really confused.
Last year I did one of those Jim Russel Racing track day/schools where you take your own car out and they teach you some track driving basics.
The first thing the instructors did was have everyone drive over to the pits and pump up tires to maximum (door sticker) pressure + 2lbs. front & rear... Any speculation on why they would do that for a track session? Sounds like most guys here are using lower pressures for the track.

Matt Lane

I could only guess they wanted you to learn at lower speeds with the absolute minimum traction possible from your tires? You'd be running on the centers at those pressures, I'd think.

Track pressures are dictated by optimal HOT tire pressures, which in turn vary based on tire spec/compound. But if a tire likes 38 hot, then you'll have to start many pounds lower cold to account for the buildup of pressure from hard track use and resulting heat.

M

PNogC2S

Yeah, that's why I'm so confused by this whole thing...it seems crazy to intentionally put students out on a track with tires set up for minimum traction... and it was a hot day at Infineon too boot... so those tire pressures had to have gotten pretty high!
I was on nearly new PS2's and I have to say they stuck very nicely...the instructor assigned to me, who was very familiar with Porsches, took me around a lap to show me what it could do and... WOW! the speeds were amazing (to me anyway) and we weren't slipping and drifting around... just tracked a nice clean line. Oh well...another one of those mysteries I guess.

hoggel

An engineer cannot let a discussion of numbers go by without jumping in.

Regarding recommended tire pressure in 17s vs 18s on the same car. The compressed air volume (measured at the boundary as tire pressure) and sidewall strength is what carries the car. Tires spec'd for the same car in 17 or 18 are approximately the same diameter. That means the 18s have about 15% less air volume to carry the same load. The compressibility of air is not linear so the smaller volume must be at a higher pressure to carry the same load.

When a tire hits an uneven spot/thing on the road the tire shape deflects until the air pressure inside equals the force of the impact. With a 17 inch tire there is more distance from the impact to the wheel and more air volume to compress so it can safely operate at lower air pressure. That’s why the ride is softer on 17s, they are absorbing impacts through a longer range. But that ride comes with compromised sidewall flex and contact patch.

Ed, my C2S eats rear tires. If I get 10k out of a street pair I’m excited.

My bottom line? The tire pressure depends on the car (weight), the tire size and construction, and the driving conditions (surface, temp, lateral loads, …). The factory recommendations are a conservative place to start. I run 36psi in the front all the time. At the track (DE, smooth track) I use 38psi hot in 295/30s on the rear. On the street I put 40psi cold in 285/35s to protect my wheels. Yokohama A048s on the track and Pilot Sports on the street.

24FPS

f:36
r:38-40
cold
bridgestone potenza re-11 on a cab