How to Service Rear Brakes

In the automobile braking system, the rear brakes contribute about 20 to 30 percent of the total braking power. Even though most of the braking power is in the front brakes, rear brake servicing is every bit as important as front brake servicing. Any problem with the rear brakes that is left unattended can easily escalate into a serious safety concern. Rear brakes can be either disk or drum type brakes, and the weekend mechanic should be familiar with basic maintenance procedures for both types of brakes.

Instructions

Disk Brake Service

1

Park the vehicle on a level surface. Do not set the parking brake. Securely block the front wheels to prevent accidental vehicle movement. Slightly loosen the lug nuts then jack up the car. Support the vehicle securely on a jack stand. Completely remove the lug nuts and pull the wheel off.

2

Remove the two caliper guide rod bolts. Sometimes there are protective rubber caps on the bolt heads. These can simply be pried off. Firmly grip the caliper with both hands and roll it back and forth a few times to separate the brake pads slightly. Remove the caliper assembly from the disk and hang it out of the way with a bungee cord. Be careful not to stretch or damage the flexible brake line.

3

Slide the brake pads and shims out of the caliper. If retaining clips are present, these can be pried off with a screw driver or pulled off with pliers. Be careful to not damage the clips during removal.

4

Retract the piston back into the cylinder by hooking the frame end of a large C-clamp on the back of the caliper, placing the spindle swivel of the clamp on the piston face, and tightening the clamp. Be careful not to pinch or damage the rubber piston boot. For rear brakes with the parking brake incorporated into the brake cylinder, hook a large C-clamp over the back of the caliper, and position the clamp spindle swivel on the piston face. Tighten the clamp to put firm pressure on the piston, but do not try to force the piston back. Grip the piston with large channel lock pliers, and rotate the piston clockwise to screw it back into the cylinder. Maintain the backward pressure on the piston by tightening the C-clamp after every piston rotation. Be careful not to damage the rubber piston boot.

5

Measure the disk thickness at several places using the brake disk micrometer. Examine the disk for cracks, deep scores or other damage. If the disk is irreparably damaged, or if the thickness is below the manufacturer's specified minimum, replace the disk. The minimum thickness is usually stamped into the metal around the rim of the disk. Minor disk damage can be repaired for a reasonable cost by having the disk machined at your local auto parts store.

Measure the pad lining thickness with the ruler. If the thickness is below the manufacturer's recommended minimum, or if the linings are damaged or uneven, replace the pads. The minimum thickness can be found in a suitable repair manual, which is often available at the local library. Otherwise, ask for this information at your auto parts store.

6

Remove any retaining screws or bolts from the disk, and pull the disk straight off the hub. If the disk is seized, tap the center part of the disk firmly with a rubber or plastic mallet, taking care not to hit the friction surface or outer rim.

7

Install a new disk, if needed. Liberally lubricate the caliper bolts with brake grease, before reinserting them in their mounts. Reassemble the caliper, using new pads and shims, if needed, and reinstall the caliper. Replace the wheel.

8

Repeat the procedure on the other rear wheel. Lower the vehicle. Start the engine, and pump the brakes a few times to re-extend the retracted pistons. Test the brake operation before driving.

Drum Brake Service

9

Park the vehicle on a level surface. Do not set the parking brake. Securely block the front wheels to prevent accidental vehicle movement. Slightly loosen the lug nuts then jack up the car. Support the vehicle securely on a jack stand. Completely remove the lug nuts and pull the wheel off.

10

Remove the brake drum. On many brakes the drum can be pulled right off the hub. On others, the drum may be secured by retaining screws or bolts. If so, remove these before pulling the drum off. On older brakes the drum may be secured with a single large hub nut that must be removed before removing the drum. If the drum is seized, firmly tap the outer shoulder with a rubber or plastic mallet to loosen it. If the brake shoes are pressing on the inside of the drum and preventing its removal, first be sure that the parking brake is not engaged. Next, look for a port on the backing plate with a rubber cover. Remove the cover to reveal the brake self-adjuster wheel. Reach inside with a small screwdriver, and rotate the self-adjuster to release tension on the brake shoes and back them away from the drum.

11

Measure the inside diameter of the brake drum with a brake drum micrometer. The diameter should be the same in all directions, indicating that the drum is round. Compare the measured diameter to the manufacturer's specified maximum diameter, which is usually stamped into the metal on the outside of the drum. Check the drum for cracks, deep scores, or other damage. If the drum diameter exceeds the allowable maximum, or if the drum is irreparably damaged, it should be replaced. Minor drum damage can be repaired by having the drum machined at an auto parts store. Measure the shoe lining thickness. Compare the measurement to the manufacturer's specified minimum thickness, which can be found in the vehicle's shop manual or aftermarket repair manual. These can usually be found at the local library. Check the brake shoe linings for damage or uneven wear, and replace if necessary.

12

Remove the brake springs. Brake springs are hooked at both ends and are removed by gripping the end of the spring with pliers and pulling to unhook it. First remove the large return springs that connect the front and rear brake shoes, followed by the smaller springs for the adjuster mechanism lever, the parking brake operating lever or any other springs that are present.

13

Remove the adjuster mechanism, and any metal struts that are sitting between the brake shoes. With no spring tension to hold them, these should slide out from between the shoes.

14

Remove the shoe hold-down pins. For pins with spring clips, grip the pin and the clip with separate pliers and rotate them until the clip releases. For pins with retaining springs, grip and retaining washer and rotate it until the notches in the washer align with the tabs on the pin end and pull the washer and retaining spring off the pin. With the retainers removed the the front brake shoe is now free and can be removed.

15

Disconnect the parking brake cable from the rear brake shoe. Pull off the retaining clip that holds the cable end, and slip the cable out of its anchor point. Pull the rear shoe off the backing plate.

16

Clean the backing plate and all removed parts with brake cleaning fluid. Use rags and a wire brush to remove stubborn deposits. Unscrew the adjuster wheel and remove the pushrod end. Clean the parts with brake cleaning fluid and lubricate the threads and the pushrod female section with brake grease before reassembling. Apply brake grease to the points where the brake shoes contact the backing plate, and the points where the brake shoes pivot on the hold-down pins. Lubricate the points where the cylinder contacts the shoes and the operating and adjusting levers pivot points. Be careful not to get grease on the drum or shoe lining surfaces.

17

Reassemble the brake by following steps in opposite order. Repeat the procedure on the other brake. Replace the wheels and lower the car. Start the engine and gently pump the brakes a few times to extend the pistons. Make a few careful stops in reverse to set the adjusters. Test the brake operation before driving normally.