Light scoring and/or wear is acceptable. If heavy scoring or warping is evident, the disc must be refinished or replaced (See Refinishing/Refacing Braking Disc). If cracks are evident in the disc, replace the disc.

BRAKING DISC REMOVAL

(1)Raise vehicle on hoist or jackstands. Remove wheel and tire assembly.

(2)Remove caliper assembly, as described under Brake Shoe Removal in this Group, (but do not disconnect brake line). Suspend caliper from wire hook or loop to avoid strain on flexible hose.

(3)Remove braking disc from the hub.

INSTALLING BRAKING DISC

(1)Slide braking disc on hub. Clean both sides of braking disc with alcohol or suitable solvent.

(2)Install caliper assembly, as described in Brake Shoe Installation paragraph.

REFINISHING BRAKING DISC

REFACING BRAKING DISC

Refacing of the braking disc is not required each time the shoe assemblies are replaced.

If the braking disc surface is deeply scored or warped or there is a complaint of brake roughness or pulsation the rotor should be resurfaced or refaced (Figs. 6 and 7).

Fig. 6 Refacing Braking Disc

Fig. 7 Resurfacing Braking Disc (Final Finish)

When refacing a braking disc the required 0.10 mm (0.004 inch) TIR (Total Indicator Reading) and 0.013 mm (0.0005 inch) thickness variation limits MUST BE MAINTAINED. Extreme care in the operation of braking disc turning equipment is required.

The collets, shafts and adapters used on the brake lathe, and the bearing cups in the rotor MUST be clean and free from any chips or contamination.

When mounting the disc on the brake lathe, strict attention to the brake lathe manufacturer's operating instructions is required.

If the disc is not mounted properly the run-out will be worse after refacing than before refacing.

The use of a double straddle cutter (Fig. 6) that machines both sides of the disc at the same time is highly recommended.

RESURFACING BRAKING DISC

This operation can be used when the disc surface is rusty or has lining deposits.

A sanding disc attachment will remove surface contamination without removing much braking disc material.

It will generally follow variations in thickness that are in the disc.

The following chart shows the location of measurements and specifications when servicing the braking disc.

All braking discs have markings for minimum allowable thickness cast on an un-machined surface of the braking disc (Fig. 8). The thickness markings may be located on the disc as shown in (Fig. 8) or on an alternate surface.

This marking includes 0.76 mm (0.030 inch) allowable disc wear beyond the recommended 0.76 mm(0.030 inch) of disc refacing.