Brake Rotors - Inspection Information: Overview
90Chevy35GMC NUMBER: 90-5-104
GROUP: 5 Brakes
DATE: October, 1990
CORPORATE
NUMBER: 065009
SUBJECT: BRAKE ROTORS: INFORMATION, REFINISHING, LATERAL RUNOUT, PARALLELISM, CALIPER INSPECTION AND BURNISHING
MODELS: 1988-90 C/K TRUCKS
In the manufacturing of brake rotors, all the tolerances regarding surface finish, parallelism and lateral runout are held very closely. The maintenance of these tolerances provide the surface necessary to prevent a loss of braking performance. C1, C2, and C3 trucks have a one piece rotor and hub assembly with loose outer and inner bearings. C1 trucks under 5600 G V W R have a 1" rotor. C1 trucks over 5600 G V W R, C2 and C3 trucks all have 1-1/4" rotors. The rotor on the K2 and K3 with C6P brakes is a complete three-piece assembly consisting of a 1-1/4" rotor, bearings and hub. The rotor on C/K3 with R05 (dual rear wheels) is a complete four-piece assembly consisting of a rotor, bearings, hub, and extension. The rotor is 1-1/4" for 1988-1989 models, 1-1/2" for 1990 models. The C3 with R05 is a one piece casting but also has 1 1/4" wide rotors for 1988-1989 models and 1-1/2" wide rotors for 90 models. The rotors on the K1 and K2 models are composite construction and require special tool J 37620 when service is required. Light scoring of the rotor surface not in excess of 0.38 mm (0.015-inch) in depth is normal, This condition will not affect brake operation.