Rotor Tolerance & Surface Finish
WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 1998 Pontiac Trans Sport, 1998 Oldsmobile Silhouette, 1998 Oldsmobile Bravada, 1998 GMC Yukon, and 1998 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.
Tolerances of the braking surfaces for flatness, parallelism and lateral runout are closely held. The maintenance of close tolerances on the shape of the breaking surfaces is necessary to prevent brake roughness or pulsation. The surface finish must be held to a specific range of 60 Ra roughness or less. The control of the surface can improve lining life. Light scoring of the rotor surfaces not exceeding 1.5 mm (0.06 in.) in depth is normal and not detrimental to brake operation.