I have a 2008 G6 base model and it has 45000 miles on it. It has brand new tires, rotors and brakes on all four. After 6 month I had to replace the back brakes again. We thought replacing the brakes would fix the problem but it did not. I was going 60MPh down interstate and you could hear a loud squeal noise coming from the tire. Hit the brakes a little bit and it goes away. When you jack up the car and freely spin the tire, you can hear a low squeal. The dealer says that it is the brake backing plate rubbing up against the rotor causing the squeal. New brakes did not fix the problem. Anyone have any idea what it might be.