Stopping the vehicle will indicate whether the brakes pull in one direction, stop straight, or require excessive effort to stop. Listening while stopping permits a fair diagnosis of braking noises, such as rattles, groans, squeals, or chatters. Visually inspecting the parts provides valuable information on the condition of the braking system.

A complete disc brake service typically involves four major operations, which are as follows:

Replacing worn brake pads
Rebuilding the caliper assembly
Resurfacing the brake discs
Bleeding the system

Depending on the condition of the parts, the mechanic may need to do one or more of the operations. In any case. you must make sure the brake assembly is in sound operating condition.

Disc Brake Pad Replacement
Disc brakes have flat linings bonded to a metal plate or shoe. The pad is not rigidly mounted inside the caliper assembly; thus, it is said to float. These pads are held in position by retainers or internal depressions (pockets machined into the caliper).

A visual inspection on the condition of the pads can be made after the wheel and tire is removed. The inner shoe and lining can be viewed through a hole in the top of the caliper, whereas the outer shoe and linings can be viewed from the end of the caliper.

A good rule in determining the need for pad replacement is to compare lining thickness to the thickness of the metal shoe. If the lining is not as thick as the metal shoe, it should be replaced. The basic steps for disc brake service are as follows:

1. Siphon two thirds of the brake fluid from the master cylinder. This action prevents fluid overflow when the caliper piston is pushed back.

2. Remove the caliper guide pins that holds the caliper to the adapter. In typical applications, positioners and bushings will come off with the pins.

3. Lift the caliper off the adapter and away from the rotor. Do NOT let the caliper hang by the brake hose. Hook or tie the caliper to a suspension member. This will allow the rotor to be tested and inspected.

4. Remove old pads from the caliper and adapter. Note the position of antirattle clips because they may be reused if they are in good condition.

5. Using a C-clamp or large screwdriver. force the piston back into the caliper. This action will open the caliper wide enough for new, thicker pads.

6. Install the antirattle clips on the new pads. Fit the pads back into the caliper.

7. Slide the caliper assembly over the rotor. Assemble the caliper mounting hardware in reverse order of disassembly. Make sure all bolts are torqued to the manufacturer's specifications.

8. After new pads are installed, road test the vehicle to make sure that the brakes are operating properly and also seat the new pads. Several (3 to 3) heavy braking applications will work.

NOTE
It is acceptable to service just the rear or front disc brakes. However. NEVER service only the left or right brake assemblies; always replace both sets to assure equal braking action.

Since disc brake systems vary, consult the vehicle manufacturer's service and repair manuals for specific details on the type of disc brakes you are working on.