I removed my stock turbo rims to clean them, and cracks on the inner sidewalls were noted on both rear tires. Obviously, this was not a good thing to see. My 02 Turbo has the stock size 295-30-18 Potenza RE050A Pole Positions on stock hollow spoke turbo wheels with stock suspension. I purchased them in Feb 07 and have about 75% tread remaining. These tires have been used on street only and have been maintained at the Porsche spec of 44 psi. I am sending them back to the Tire Rack as their tech has viewed the photos and feels that there could be a defect in manufacturing.

The cracks are near the junction of the tread and sidewall and run circumferentially as shown in the picture. They are located on the inner sidewall only, so removing the wheel is the best way to see the cracks. No cracking was observed on the front tires.