I have recently purchased a 2006 certified MB S500 with Sport Pkg and 34k on it. Pilot Sports on the front have 20k on them and only half worn. The set on the back were bare after 8k. Purchased Goodyear F1 Assymetrics and they were bare after 8k (actually 8k on the right rear, left rears lasting about 11k). Is this normal? I don't drive the car really aggressively. Wanted to go with the Pilot Sport A/S but they only come in 275/40-18's instead of 265/40-18's. Any unforeseen issues with running 275's instead of 265's?