See Figures 1 and 2
Support the front suspension or axle on jackstands and remove the wheels. Look in at the ends of the caliper to check the lining thickness of the outer pad. Look through the inspection hole in the top of the caliper to check the thickness of the inner pad. Minimum acceptable pad thickness is 1 / 32 in. (0.79mm) from the rivet heads on original equipment riveted linings and 1 / 2 in. (12.7mm) lining thickness on bonded linings.
These manufacturer's specifications may not agree with your state inspection law.
All original equipment pads are the riveted type; unless you want to remove the pads to measure the actual thickness from the rivet heads, you will have to make the limit for visual inspection 1 / 16 in. (1.6mm) or more. The same applies if you don't know what kind of lining you have. The 1974-86 original equipment pads and GM replacement pads have an integral wear sensor. This is a spring steel tab on the rear edge of the inner pad which produces a squeal by rubbing against the rotor to warn that the pads have reached their wear limit. They do not squeal when the brakes are applied.
REMOVAL & INSTALLATION
The caliper has to be removed to replace the pads. Please refer to the caliper removal and installation procedure. Skip steps 8-10, as there is no need to detach the brake line.