From my past experience and what they found, the lugs had been tightened very unevenly and the mechanic said it was probably from someone with an impact set extremely too high and running the first one down to full torque. Another factor they stated may have been heat. This was on a Ford 3/4tonHD pulling a fifth wheel trailer. (It is very nerve wracking to be pulling a load like that and when you have really lean on the brakes, they start to shudder.) All of this happened after having a new set of tires installed. (That series of vehicle has self-locking lugs.)

Maybe it was a combination of factors, but all they did was replace the front rotors and the brakes started operating smoothly again.

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Sam

84 300SD 350K+ miles ( Blue Belle )