How to Adjust Drum Brakes

by Jody L. Campbell

Drum brakes are used only on the rear of some vehicles. Today, many vehicles are being manufactured with four-wheel disc brakes. Vintage cars were made with four-wheel drum brakes, but the braking response was not as good as that of disc brakes. With that in mind, drum brakes only supply the vehicle with up to 25 percent braking capacity. That means the front disc brakes do most of the work. If the rear drum brakes become unadjusted (and there are a few common factors that account for that), the front ones begin to overcompensate. Problems in the front brakes can become apparent if they're overworked. Keeping the rear brakes adjusted is a safe and effective way to balance the braking system and increase the longevity of your front brakes.

Step 1

Remove the hub caps from the rear wheels and break the lug nuts loose with the lug wrench.

Step 2

Lift the rear of the vehicle with the floor jack and secure it onto the jack stands.

Step 3

Remove the nuts and wheels.

Step 4

Locate the adjusting porthole on the back of the backing plate. There should be a rubber plug capping the porthole to protect it from the elements. Remove the plug by prying it out with a screwdriver.

Step 5

Insert the long screwdriver into the porthole and feel your way around for the adjusting retainer clip. If necessary, grab a flashlight and crawl under the vehicle to look for it. It's a small lever that holds the star wheel in position. Depress the clip with the screwdriver away from the star wheel and use the brake spoon adjuster (or another straight-edge screwdriver) to turn the star wheel in one direction.

Step 6

Spin the drum by hand. If the tension is increasing, you're going the right way to adjust the brake shoes. If the tension is decreasing and the drum is spinning more freely, you're un-adjusting the shoes. Go back and use the spoon to turn the star wheel in the opposite direction.

Step 7

Occasionally, between making adjustments, yank on the parking brake cable near the rear of the backing plate to center the shoes.

Step 8

Continually check the tension of the shoes against the drum by spinning the drum (every four to five turns of the star wheel). The drum needs to move, but there should be a dragging sensation on the drum from the shoes contacting the inside diameter of the drum as you spin it. Adjust the brake shoes upward so the drum cannot complete a full revolution of spinning on its own (or half a revolution, if desired).

Step 9

Repeat this procedure for the other side.

Step 10

Carefully get into the vehicle and apply the brake pedal and parking brake mechanism simultaneously. This will center the shoes and integrate the parking brake mechanism.

Step 11

Apply the parking brake and let it sit. Check both rear drums to make sure they're holding correctly. If one is holding and the other isn't, you need to locate the equalizer of the parking brake cable and adjust it. Refer to the repair manual for your specific vehicle for the correct procedure.

Step 12

Readjust both sides after you have pumped the foot brake pedal while applying the parking brake mechanism, and adjusted the equalizer if applicable.

Replace the porthole plug when finished. Replace the wheels and lug nuts and tighten.

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