I have a 2012 convertible V6. I had a guy put new brake pads and turn the rotors about a month ago. Now when I am in the mountains and coming down through curves, there is a clacking noise that changes as you apply the brakes. It sounds like brake pads slapping against something but removing the wheels, I see nothing loose or looking out of place. There are no marks on calipers or wheels. It never does it except downhill in curves. Any ideas?