For 1990-2009 cars

Inspect the brake linings at 10,000 km (6,000 miles), then every 20,000 km (12,000 miles), and any time that the wheels are removed (tire rotation, etc.). Check 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 wear normally occurs. However, at the same time, check the lining thickness on the inner pad to make sure that it has not worn prematurely. Look down through the inspection hole in the top of the caliper to view the inner pad. Whenever the thickness of any lining is worn to 2.0 mm (0.08 in.) or less at either end of the shoe, all disc brake pad and lining assemblies should be replaced at the same time.