Disc Brake Rotor: Inspection

WARNING: This page is about a different car, the 1990 Saab 9000 and 1989 Saab 9000. However, it is still accessible from the selected car via links, so may be relevant.

With rotor installed and hub nut correctly tightened, check disc runout. Mount dial indicator with pointer positioned at center of disc pad contact area of rotor. Check runout while slowly rotating rotor by hand.
Standard front and rear brake rotor runout is .0031" (.078 mm) or less. If runout is beyond specification, resurface or replace rotor as necessary. If rotor is in good condition, resurface to no less than minimum thickness specification. Check rotor for proper thickness and parallelism.
Using a micrometer, measure rotor thickness at 12 points, about 30 degrees apart at center of disc pad contact area. Replace rotor if worn to more than discard specification. Ensure that when rotor thickness measurements are taken, the difference between any measurement (parallelism) is not more than .0006" (.015 mm).

CAUTION: If parallelism is more than specification, resurface rotor to no less than the minimum thickness. Ensure that the grinding depth for any one side is no more than .04" (1.0 mm) on front and .028" (.7 mm) on rear.