[JET]

Originally Posted by Carlos

Usually the rotors need to be machined if there is runout on them. This is sometimes easy to detect when driving a car as the brakes will seem to shudder as the rotor is not as thick all the way around. If the rotors are off, measure them with a micrometer (assuming disk brakes) at several different points to see if runout is present (numbers are not equal). As stated above, turning (or machining) the rotors is the most economically sound option as it only costs $10/rotor at checker. There is no need to replace them unless they are under the minimum thickness spec. Checker can measure them and check them if you have no idea what you are doing at all. They would then sell you new rotors of turn them.

Once again, this is wrong. Runout is not from the brakes being a different thickness. Runout is from a warped rotor. A rotor can be warped and still be the same thickness all the way around. Acutually they usually are. Runout is measured by putting a dial indicator on the brake caliper and putting the measuring end on the rotor, and then spinning the rotor. The difference between the high and low reading is the amount of runout. Then you need to do the same on the other side of the rotor. Add those 2 measurements together. Measure the thickness of the rotor, then subtract the 2 measurements from it. If that is still above the minimum thickness, then you can turn it down. If it is lower than the minimum thickness (more than likely) then you cannot turn it down.