I own a 2011 Sonata which I bought new. It now has 21000 miles on it and all four tires have flat spots (cupping). The noise is so bad that I am getting ready to buy new tires to reduce the noise. The car has no noticeable vibration or pulling. Tire have always been properly inflated. Both front and rear tires are effected. From what I can learn on forums and at a tire dealer, cupping is caused by suspension problems (bad shocks, improper balancing or bad wheels). Has anybody had similar problems?