GM Service Manual Online
For 1990-2009 cars only

Inspect the brake linings approximately every 10 000 km (6,000 mi) and any time the wheels are removed, including tire rotation, etc. Replace the brake linings before the rivet heads become exposed and score the brake drum. Replace the brake linings when the thickness of the brake lining is 6.3 mm (0.250 in) at the thinnest point. Always replace the brake linings as a complete axle set.

The brake linings should be free of grease and oil and show at least 70 percent contact area over the braking surface in order to indicate good brake lining contract.

Remove any shiny glazed spots with an emery cloth while wearing a dust mask. Wipe the brake lining clean with a damp cloth.