GM Service Manual Online
For 1990-2009 cars only
  1. Inspect the brake linings every 9654 km (6,000 mi).
  2. Inspect the brake linings whenever the tire and wheel assemblies are removed , such as during a tire rotation.
  3. Inspect both ends of the outer pad by looking in at each end of the caliper. These are the points at which the highest rate of pad wear normally occurs.
  4. Inspect the lining thickness on the inner shoe for premature wear. The inboard shoe and linings may have a thermal layer against the shoe which is molded with the lining. Do not confuse this layer with uneven inboard/outboard lining wear.
  5. Look down through the inspection hole in the top of the caliper in order to view the inner shoe.
  6. Replace the disc brake shoe and lining assemblies when the thickness of any lining is worn to within 0.76 mm (0.030 in) of the shoe. For riveted shoe and lining assemblies, replace the lining if it is worn to within 0.76 mm (0.030 in) of any rivet head.
  7. Replace all of the disc brake shoe and lining assemblies at the same time.