Rear Brake Disc Inspection

Runout


1.Raise the rear of the vehicle, and make sure it is securely supported. Remove the rear wheels.

2.Remove the brake pads.

3.Inspect the disc surface for damage and cracks. Clean the disc thoroughly and remove all rust.

4.Use wheel nuts and suitable flat washers (A) to hold the disc securely against the hub, then mount a dial indicator (B) as shown, and measure the runout at 10 mm (0.4 in.) from the outer edge of the disc.

Brake Disc Runout:
Service Limit: 0.10 mm (0.004 in.) 

 

5.If the disc is beyond the service limit, refinish the brake disc.

Max. Refinishing Limit: 8.0 mm (0.31 in.) 

NOTE: A new disc should be refinished if its runout is greater than 0.10 mm (0.004 in.).

Thickness and parallelism


1.Loosen the rear wheel nuts slightly, then raise the vehicle and make sure it is securely supported. Remove the rear wheels.

2.Remove the brake pads.

3.Using a micrometer (A), measure disc thickness at eight points, approximately 45° apart and 10 mm (0.4 in.) in from the outer edge of the disc.

This is the maximum allowable difference between the thickness measurements.

 

Brake Disc Thickness:
 Standard: 8.9-9.1 mm (0.350-0.358 in.) 
 Max. Refinishing Limit: 8.0 mm (0.31 in.) 

Brake Disc Parallelism: 0.015 mm
(0.0006 in.) max.
 

4.If the smallest measurement is less than the max. Refinishing limit, replace the brake disc.

5.If the disc is beyond the service limit for parallelism, refinish the brake disc with an on-car brake lathe. The Kwik-Lathe produced by Kwik-way Manufacturing Co. and the ‘‘Front Brake Disc Lathe'' offered by Snap-on Tools Co. are approved for this operation.