Brake discs should be inspected for thickness at a number of spots around the braking surface with a micrometer. If the thickness AT ANY POINT is less than the minimum given in the Brake Specifications Chart, the disc must be replaced. Roughness or significant grooving is also reason to replace the disc.
The disc should also be checked for run-out. With the disc installed (hold it with two lug nuts if necessary), mount a dial indicator to the shock and zero it with the tip in contact with the braking surface on the disc about 0.60 in. (15mm) from the edge. Rotate the disc slowly. Read the indicator; the limit for run-out is 0.006 in. (0.15mm). The disc must be replaced if run-out exceeds this amount.