Be very careful tightening down the lug nuts. If you have a torque wrench, use it. If you don't have, or don't want to buy one (about 80 bucks), find a friend who has one. Costco can tell you how many inch/pounds to torque to. BMW rotors are very thin and do not take a lot of pressure. Use to be a regular problem with my '91 325i, until I found out to not trust the tire company's torque sticks. Costco re-calibrates theirs every day.