When I bought the truck, the front end shimmied when the brakes were applied, so I had the rotors turned. 1500 miles later the front end again shimmied. so off to a new brake shop. They found that half of the rear brake cylinder on both wheels was not working, so they rebuilt the rear brake cylinders and turned the front rotors. Last week, and 1500 miles later, good old shimmy again, so back to the brake shop. This time a new mechanic tells me that my front brake lines are not allowing the fluid to drain back quickly after the brakes are applied, which he checked by opening the bleeder screw after applying the brakes, which then released the pressure. Without releasing the bleeder screw, the brakes would stay on (drag) for a while. If the bleeder screw did not release the pressure, the problem would have been sticking calipers. I had heard of sticking calipers which is what I suspected all along, but had not heard of faulty brake lines. This mechanic said he has been doing brakes for 21 years and has seen this many times, the brake lines failing from the inside. I hope he is right. At this rate, I won't ever have to worry about my front wheel bearings wearing out as they have been repacked three times in three months.