Lumina APV V6-191 3.1L (1990)
Brake Rotor/Disc: Service and Repair
Servicing of disc brakes is extremely critical due to the close tolerances required in machining the brake disc to insure proper brake operation.
The maintenance of these close controls on the friction surfaces is necessary to prevent brake roughness. In addition, the surface finish must be
non-directional and maintained at a micro-inch finish. This close control of the rubbing surface finish is necessary to avoid pulls and erratic performance
and promote long lining life and equal lining wear of both left and right brakes.
In light of the foregoing remarks, refinishing of the rubbing surfaces should not be attempted unless precision equipment, capable of measuring in
micro-inches is available.
To check runout of a disc, mount a dial indicator on a convenient part (steering knuckle, tie rod, disc brake caliper housing) so that the plunger of the
dial indicator contacts the disc at a point one inch from the outer edge. If the total indicated runout exceeds specifications, install a new disc.
When refacing rotors on 1988 K1-2 models it is extremely important that the rotor is mounted on the lathe exactly as it is mounted on the vehicle. To
accomplish this, rotor adapter tool No. J-37620, or equivalent must be used. Failure to use this tool can result in non-parallel rotor surfaces. This
condition can cause brake pedal vibration or pulsation.
