vvvince Knauf

We had a big problem at the Parade Autocross.
Power on oversteer. Big time.
This car is stock (one of the bunch of Speed Yellow GT3s there).
Pilot Sports PS2 tires. NO changes in springs, stock bar settings etc.

We drove a car (997 C4S) with these at the Michelin experience next door=WONDERFUL.

It has NEVER had power on oversteer in the dry. Neutral at atx events if driven reasonably. (i.e. careful in first gear.)
First run, Power On OVERSTEER.
I verified and corrected tire pressures. Better but still BAD. My wife and I NEVER got a good run because of this. We couldn't put any power down except when driving straight.
We have been driving instructors for at least 15 years each. We know how to drive.

Inspection revealed appropriate wear pattern on the rear tires EXCEPT that there was cord worn through on the inner one inch of tread.

Otherwise they varried from 6/32 at outside edge to 4/32 one inch away from the worn through the cord inner edge.
VERY SCARRY and confusing.

History=The first set of tires (also PS2) did the same thing with about 12,000 miles on the car. We found that all four corners had incorrect alignment settings from the factory. They bought us one of the two new rear tires and re aligned the car.
Now we have with 23,500+ miles on the car and again ~12,000 miles on the rear tires. Hmm. BAD PATTERN.

We checked the alignment and found all was to factory spec except rear toe in. It measured 1/4 inch (8/32 inch), with factory spec of 26' (minutes) or ~ 5/32 inch. We adjusted it to 4/32 inch, and put new PS2s on the rear.

Fronts have 5-6/32 inch tread depth. These are the original factory tires!

HAS ANYONE HAD ANY EXPERIENCE LIKE THIS?
i.e. wear through the cord on the inner edge only, with good tread depth on remaining of tire at about 12,000 miles, with PS2s.

Any thoughts? Advice?

Most Porsches at the Parade were on Michelin's. Most on PS2's

Thanks for your help.
vvvince Knauf
vvvince@aol.com
San Diego

Holger B

Seems completely normal to me that the inner edge of the rears wear out first given all the weight back there and the fact that you need to have some negative camber. Happens on my GT3 and also my prior 996 C2.

On the bright side, I think you're getting a lot more mileage from your tires than the average GT3 owner. Not enough track time?

vvvince Knauf

We are getting 12,000 miles, not horrible, BUT the only part that wears out is the inner one inch!. The rest shows a bit more wear on the inner edge than the outer edge, but going from 6 to 5 to 4 /32nds to -1/32 is VERY abrupt.

Is this the wear pattern that others experience?

thanks
vvvince Knauf
San Diego

mxdave74

seems normal to me given your autoxing ways. you'd get a little more even wear is speeds were higher, but with a steady diet of tight courses you're inevitably going to toast the insides well before the rest of the tire is done.

plima

I have 32K miles (street+autocross, no track) on my '04 GT3; all PS2 miles. I got 12K miles on the first set of rears, but under 10K on the next 2 sets, and they do wear out on the inside if you are mostly driving on the street. If you want (somewhat) better mileage (at the expense of awesome at-the-limit handling) you can have the rear camber reduced a bit.