How to Adjust Rear Brake Shoesby KevinM
Although the inner workings of a drum brake look complicated, the operating principle is actually simple. When the driver pushes on the brake pedal, a hydraulic cylinder in the brake pushes two semi-circular brake shoes outward until they touch the inner surface of a drum that is attached to the rotating wheel, and the friction slows the vehicle. When the driver releases the brake pedal, the brake piston retracts and a number of springs pull the brake shoes away from the drum. Optimal operation of a drum brake requires that the brake shoes be located as close to the drum as possible without actually touching it when the brakes are not being used. Proper adjustment of the brake shoe position can help to improve drum brake performance.
Park the vehicle on a firm, level surface. Block the front wheels to prevent accidental rolling. Put the automatic transmission in park or manual transmission in first or reverse gear as applicable. Do not set the emergency brake. Loosen the lug nuts on the wheel to be serviced about one full turn and then jack up the vehicle. Support the vehicle securely on a jack stand and complete the removal of the wheel.
Look for the brake shoe adjustment port. This will be a slot or a hole about 1/4- to 1/2-inch in diameter in the the back of the backing plate or sometimes on the front of the brake drum. The port is usually located lower down on the backing plate or drum, and it normally has a rubber cover to keep dirt and moisture out of the drum. Remove the cover from any ports you find and look inside, using the flashlight. You should see the brake self-adjuster mechanism, which is a long cylinder (like a small pipe or tube) with a gear around the outside, and a spring-operated lever that engages in the gear teeth. Note that if the port is on the backing plate it will be aligned with the self-adjuster, and if it is on the drum you will have to rotate the drum until the port and self-adjuster are aligned.
Rotate the brake drum with your hand and check for resistance. If the brake shoes are dragging on the drum you will feel resistance, and you will feel, and perhaps hear, the rubbing. Reach in through the adjustment port with a small screwdriver or pick and rotate the self-adjuster wheel to move the brake shoes in or out as desired. Repeat the rotation of the drum to assess the effect of your adjustment. You should move the shoes out until they just begin to contact the drum and then back the self-adjuster off about three or four clicks. On some brakes you will have to use two screwdrivers to perform the adjustment; one to lift the adjuster lever and the other to rotate the self-adjuster wheel.
Replace the wheel and lower the car. Repeat the operation to the brake on the other side.
Items you will need
- photo_camera Car Brake image by Joelyn Pullano from Fotolia.com