Tire rotation revealed both rear original equipment were cupped. My good hearing wife first advised me of tire noise at 9k miles, at 15k the sound was clear to all. Service tech had mechanic drive car who just confirmed the noise was tires and inspection confirmed cupping "but there is still good tread ". I wanted to know why it was cupping, didn't want replacement tires doing the same thing. "I am sooo sorry but it is those hanuck (?) They put on new cars". I'm concerned that some defect in the rear wheels may be the problem. Tire dealership did alignment and results were perfect. Ideas???