My rear tires are continually cupping on the outside of the tires which are creating a roar sound. I have had two four wheel alignments done by a locally reputable shop (by my location's standards, not a dealer). I did a search online on tire cupping and it was mentioned that bent or worn suspension parts are often the culprit. I got the car with 89,000 miles on it and it now has 145,000. I have not done any off roading. The other possibility according to the Haynes manual is the possibility of worn bearings. When I put the rear tires to the front then it roars up there and begins to cup the ones put to the rear. Need to get this fixed, don't think my tires are going to hold up very long.