MY wife drives a 2004 GP GTP. We bought it used with 17k on it. Rear tires were bald on the inside, dealer put new tires on all 4 corners. Since then, we have had to put on another set of tires at 40k. This car eats rear tires up. It has what seems to be a camber issue in the rear. We have had it aligned at a few shops but they say the camber is within GM specs and to rotate the tires every 1500 miles. I have started putting the cheapest tires I can find since we only get 20k out of a set before the inside is bald. Does anyone know a solution to fix this issue?