Air Brake Disc Caliper problems of the 1999 Jeep Grand Cherokee

I have had to have the dealer replace/machine the front rotors every 8 - 10,000 miles since I purchased the the vehicle new. They have given me all kinds of excusses from ware and tear to driving inrain cause the rotor to warp when they are hot and hit water. I think it the caliper that are problem and not the pad or rotor.

Violent shaking in steering wheel when brakes are applied at speeds of 50 mph or more.