Sorry to post this. The search button doesn't seem to work. I'm trying to help out a friend. He is experiencing shaking when braking which automatically suggests his rotors are warped. I recently changed his pads two weeks ago front and rear. I didn't see any big signs of hot spots or I might have overlooked it. But my question is, what other way can you check or properly diagnose a bad rotor? Any tools or tricks?

 

I thought you were suppose to lathe the rotor everytime you change the pads.

 

No you don't have to. Only time to cut it is when you scorn the rotor but taking material off the rotor is actually not good. The rotor just becomes more susceptible to warping b/c there is less material. Think Thermal.

 

Oh, my mechanic told me that. Sorry I wasn't helpful.

 

Have the rotors cut, or replaced..

 

Well I purchased a micrometer. Will be checking variable thickness.

 

Rotors typically don't warp. This is sort of a brake myth. 99+% of the vibrations that people experience upon braking are uneven deposits of pad material on the rotors. This is caused by stopping on hot brakes. You can try and perform some hard cold stops on abrasive pads, or you can sand, lathe or replace the rotors and the problem will go away (sanding is iffy, you've got to sand the hell out of it).