I'm running Michelin Pilot Sport AS Plus tires on the front (good tread) and Kuhmo's (nearly worn out) on the back. 235/45-17 all around. This is how I bought the car. The rears need to be replaced soon (about 3/32 [2.5 mm] tread left, just above the wear bars). I was at Costco yesterday and saw a sign from Michelin suggesting that if you replace two tires, they should go on the back axle. Their rationale is that you want the deeper tread and better hydroplaning resistance on the back axle. I always thought you'd want the better tires on the front, because if you loose steering, nothing else matters. I also noticed that in the BMW owner's manual it suggests *not* rotating the tires. I'm looking for some experienced E39 opinions on this. Which tires wear faster, front or back axle? Are the wear patterns even enough that rotation is not needed? Also, any opinions as to the choice between Michelin Pilot Sport PS2 (summer) and Pilot Sport AS Plus (all-weather)?