I bought my 997 C2 with about 7500 miles. I'm now close to 9000 and my rear Pirellis P1 Rosso are gone. No thread in the center of the tires. I checked tire preassure about 500 miles ago and they were under inflated. Front tires were also under inflated but still have some thread on them. I guess it is a combination of under inflated and the weight of the car on the rear tires that ended up damaging the tires.