Q: How to inspect and replace a disc on a Chevrolet Impala and Monte Carlo?
A: The disc and the hub flange usually have a thin plate between them that is installed by the manufacturer to correct disc runout. The V-notch should be used to mark the stud before removal of the plate. To check for excessive runout, measure it with a plate and disc in place, if indeed it has to be machined or changed. Take off the plate if there is excessive runout, then recheck. Before starting inspection loosen lug nuts on wheels, raise and secure vehicle using jack stands, and remove wheel. Remove brake caliper and support it out of the way. Reinstall lug nuts temporarily to hold the disc against the hub; look through it for any damage on its surface. The disc should be checked on both sides since sometimes it may need refinishing or replacing as well as warping due to heat transfer during braking. Place dial indicator near outer edge of disc and turn disc while checking its runout percentage In case indicator reading exceeds 0.003 inch value, this means that the rotor must either be refinished or replaced as appropriate otherwise you can deglaze Brake Pad surface with sandpaper If not below minimum required thickness do not machine disk People take disc out by removing caliper mounting bracket in relation to hub which they also mark Clean inside of disk and hubs flange then secure disk Tighten bolts on caliper mounting bracket plus calipers Replace wheel back down slowly tighten lug nuts again use your brakes gently until you are sure about how they work properly.