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An Overview Of How A Contractor Can Replace The Drum And Brakes On A Large Truck With Air Brakes

22 November 2016 by Herman Mills

Maintaining your own equipment is one of the best ways to control your operating costs and increase your profits. You should learn how to do basic chores like changing the drums and brakes on the large trucks you own. Replacing the brakes on a large truck is different from changing brakes on a pickup truck, but it is something you should be able to do on your own. If you know how to change a tire but have never changed the drum and brakes on a large truck, here is an overview of what you will have to do after you remove the tire.

Release Brakes

You need to release the brakes in order for you to be able to take off the brake drum. Place chocks on a couple of the wheels so the truck won't roll and press the brake release button down in the cab. You now need to adjust the slack on the brakes. The slack adjuster is a square nut located on the air canister for the brakes right by the wheel.  You will need a 3/8" box wrench to move the nut.

There is also a little button on the back side of the air canister that needs to be pulled and held out before you can adjust the slack. Move the wrench on the adjuster nut until the button pops out and then put a small pair of needle-nose pliers on the stem of the button to keep it open.

Move the adjuster nut back and forth until you see the brake shoes recede from the drum. The adjuster mechanism works on a ratchet-type of system.

Take Off Brake Drum

The brake drum is the large round metal part the covers the brake shoes and axle. You may have to pound the drum with a sledgehammer to loosen it. Once the drum is loosened, you can slide it off the axle to expose the brake shoes.

Remove Brake Shoes

You need to remove the pins holding the brake shoes to the truck. Slide a pry bar in between the pin and the wire on the pin in the front of the upper brake shoe. Push the bar back behind the spring connecting the upper and lower brake shoes together and use the axle as leverage to lift up the brake shoe. Lift up the brake shoe and pry the pin out of the groove the pin is in on the brake shoe with a long flathead screwdriver. Now, pry the bottom brake shoe down and remove the other pin. Remove the spring connecting the two brake shoes together. The backend of the shoes is also held together with a spring, but you can take both brake shoes off of the brake bracket without removing this spring.

Installing New Brake Shoes

There is a groove on the backend of the each brake shoe that go on anchor pins on the brake bracket. You should change the anchor pins before you put on the new brake shoes. Pound out the rollers with a hammer. Put some anti-seize compound on the new anchor pins and put them back into the bracket.

Set the backend of the top brake on top of the anchor pin and wrap it over the top of the brake bracket. Connect the backend of the lower brake shoe to the top brake shoe with the spring and wrap the bottom brake shoe around the bottom of the bracket. You now need to put the spring back on the front end of the brake shoes. Connect the two shoes together with the front spring.

Put the new pins into grooves in the front of the brake shoes. The pins have a wire on them with what looks like bent elbows. The elbows slide into holes in the shoes to help keep the pins in place.

Install New Drum

You want to clean the inside of the new drum with brake cleaner before you put it on. Sometimes a manufacturer will spray the drum with a rust inhibitor so the drum won't rust while being stored on a shelf. The inhibitors can affect the ability of the shoes to stop the drum from turning around so you can stop the truck when braking. Place the new drum on the truck.

Adjust Shoes

Move the adjuster wrench until the shoes rise up against the bottom of the drum. Remove the needle-nose pliers from the button so it drops back into place in the air canister to finish the job. For assistance, talk to a professional like C L Enterprises.

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