stiles_s

Interesting -- not so in the non-S? All the more reason for me to get an S!

dstrimbu

The manual for the 997S makes a distinct reference to running race-compound tires on the M97 motor...

"The fitting of racing tires (e.g. slicks) for sporting
events is not approved by Porsche. Very high cornering
speeds can be achieved with racing tires.
However, the resulting transverse acceleration
values would jeopardize the adequate supply of oil
to the engine.
Porsche therefore will not accept any warranty or
accept any liability for damage occurring as a result
of non-compliance with this provision."

The PSC is not a 'slick', now is it? And the M97 doesn't have a real dry sump lube system, either... sooooo, it's up to you. I would think that, if you can drive the car hard enough to starve the oil system, you belong in a GT3.

-don

Alan Smithee

Definitely not...DOT approved, and Porsche approved...they even offer/suggest the PSCs on 19" Carrera Sport wheels as an accessory.

dstrimbu

...and the PSCs are probably the tire of choice if you live in a dry climate. I've heard some marginal things about them in the rain, Alan.

Crazy Canuck

I find 42 hot on PS2s really slippery.

Deanski

I'm wondering how these Yokohama tires are? FBL runs these on both the Cayman GTR and the new GT3'S that they mfg. They have very god results from them after speaking with Chip and Spencer. Not sure which ones.

On another note, I see Pirelli has new P-Zero Rosso's out now. The ones on my car now seem very hard that's for sure. I wonder wat they changed from old/new?

I'd love to have a set of the M Sport Cups for days at the track (if I ever get time damn it).

I really need to have FBL tweek my car one day. The new Bilsteins would be a nice option. One of the members had them on his C2S over at FBL. It was the basalt black one.

Ah the things we do to go fast and stay on the track!!

Deanski

Dr. Car

R-comps seem to help the front axle more than the rear on many cars, so you may find that tires alone will change the balance.

I plan to see what spacers on the front axle only will do for front end grip. By putting the wheel farther outboard, it increases the fulcrum of the front suspension arms and thus increases mechanical grip. Theoretically.

I totally agree with maxxing out the front camber. I am running 1.2-1.3 neg. front (all I could get), a bit under 2.5 neg. rear, 2mm total toe out front and 3mm total toe in rear (total values). Ran high pressures on PS2s (a few pounds over the values on the door sticker) and was mostly happy in auto-x, I found it easy to provoke the car into drifts and oversteer, but that is only in 2nd gear.

- Ted

fuenfer

Sorry to resurrect this thread, but I was hoping to see if anyone had any further insights into "track" alignments for the 997S.

I recently had my car aligned, and the max negative camber for the fronts that we could get was 0.7 degrees. Is there an adjustment that my shop may have missed that would allow us to get the 1.2/1.3 of negative camber others seem to have gotten?

We also set the rear camber to -1.9 degrees or so -- IIRC, that was a bit more negative camber than what the factory recommends. I was thinking leaving it at 1.9 would likely work fine, since I'm also experiencing some understeer, but would like to hear your opinion.

Otherwise, I don't think we touched the caster settings at all (they were as per factory) -- don't know if they're even adjustable. We dialed in about .02 degrees of toe-out, which I've been told would improve turn-in.

WaltB

Another reason to have a C4S? Keep the power on in the turn and let the front end pull you around. No understeer problems.

Mr. Brown

I race a FWD 1999 Honda Civic in the SSC class in SCCA races. The trick to get FWD cars to rotate is to pump up the rear tires. The rules won't let us modify suspensions and, in the Civic, there's very little camber available, so we run with cold air pressures of 33F and 37R. In a Neon I used to race, I would run with over 40 psi in the rear.

When I got my 2004 M3 I played with air pressures and ended up setting them at 35F and 42R. This was on a car with the factory alignment and Michelin Pilot Sports. At the Summit Point track in WV, with these air pressures, I got NO understeer in the M3.
Mr. B

Crazy Canuck

GT3 is dry sump. Completely different engine.

When I went with 8.5" front rims on the S with the 235 tires I was told by Dave at Wheel Enhancement that it would reduce understeer a bit. It did. I noticed a difference.

A meatier front tire will help as will the varying the pressures as indicated above.

The car likes more front camber than the alignment at delivery. Once I went to a more agressive alignment the car understeered less and turned in better. It is a little twitchier though.

RonCT

Actually I don't think it works that way. The laws of physics on the race track don't change because the front wheels are driven. Traction is traction, contact patch is contact patch. I wonder if driving the front wheels might be worse - asking the tires to grip laterally in a turn and pull forward? If wheels are spinning, then you aren't getting the most you can out of your tires. I'm not very technical, but that's the layperson's version of what the Porsche racers / experts have explained - and I've read a few articles to that effect online as well.

WaltB

Ron, let's look at it this way. Let's say you were able to turn the wheels 90 degrees perpendicular. In this case your direction would be straight ahead while scrubbing your front tires. Now add front wheel drive capability as in the C4/S and although you still have scrubbing you also have a drive momentum moving the front in the direction pointed. Thus pulling the front end in the direction of the turn. I can tell you I have lots of miles on a C2 and C4S and I feel there is a big difference in having the front wheel drive aspect of the C4/S in moving the front around under power and allowing faster turns will little if no understeer.

RonCT

I want to agree with you, but the facts don't bear it out. If it did, then all Porsche track cars would be AWD. If I remember correctly, this is a complex situation involving the rear weight bias, rear wheel drive, weight distribution, etc. I remember some Porsche Race Team guys explaining it in one of our DE / Racing workshops that you simply can't ask a tire to do more than is possible. Braking and turning is asking for two things, so there's a balance point. Same with turning - and thus turning and acceleration. When you have 295 stickies on the rear of a rear-weight biased car (like the 911) and you are under full throttle exiting a turn, then there's just so much contact patch up front whether the wheels are driven or not.

Also, consider this. Dial in about 2-2.5 degrees of camber up front to erase what Porsche Marketing / Legal took away from Engineering, and you have Zero understeer in a RWD 911.

mdrums

On a dry track a C2S turns better than a C4S. In the wet the C4S is better. The way the 4 wheels drive works it will bind and not steer as good at the limit while track driving.