Hello all...I have a 2010 GT with 31K miles and recently installed a new 19" staggared wheel and tire package from American Muscle. Around that same time I also put on new drilled/slotted rotors. I have had a noticable vibration in the steering, which can also be felt from the passenger seat, worse at highway speed. Ive had the wheels road force balanced a few times, one of which they couldn't balance within the normal range. They also inspected each wheel and tire and found no abnormalities. They recommended replacing the tire on the wheel that couldn't be balanced (passenger rear), so AM sent a new tire and when installed and rebalanced the wheel is still not balanced in the normal range and the vibration is still there. I took the car back to the shop and was told by a different tech that vibration in steering would be coming from the front, so he match mounted and rebalanced the front wheels and tires and the vibration is still there. My husband visually checked the rotors and the rear are worn pretty unevenly, as in some slots are much more worn than others. Does this mean the rear rotors are warped? We did not replace the pads on the car when the new rotors were installed since the old pads still had life in them. We have already recycled the old rotors, otherwise we would just put the stock ones back on to see if the vibrstion still exists. This is SO frustrating.