Tech Talk - Maintaining Brake Systems

August is brake safety month and I think we can all agree that the brake system on a truck is one of the most important parts. A well-maintained braking system could be the one thing standing between your drivers and an accident. This is why I want to take some time to refresh you, and your drivers, on what to be looking for in a truck’s brake system during a pre-trip check.

• Brake Hoses: Make sure all brake hoses don’t have any cracks, bulges or kinks.

• Brake Chambers: When checking brake chambers, make sure that all the clamps around them are correctly seated, and are not corroded. Also look at the push rods to confirm that both brake chamber rods are set to the same length and are also correctly attached to the bracket. If you do have to replace a brake chamber, it is recommended to replace both at the same time. This will make it so that both wheel ends are doing the same amount of work.

• Slack Adjusters: Make sure the slack adjuster is securely attached to the s-cam. There should be a snap ring with some shims holding it onto the s-cam.

• Brake Shoes: Make sure brake shoes do not have any oil on them. Look for rust jacking from the brake lining to the backing plate and any cracks showing in the brake lining. At the same time measure the thickness of the brake shoes. They should be thicker than a 1/4 inch at shoe’s center or to the shoe’s wear indicator, if it has one. Checking air disc brakes is similar, but these should be over 1/8 inch in thickness.

• Drums & Rotors: On brake drums with no backing plate, you should be able to look at the drum to see how big a lip it has. Remember that the brake shoe and drum together create friction to make a truck stop. Be careful not to confuse any short hairline heat check cracks with any flexural cracks. If your truck is experiencing wheel seal failure, remove all remaining oil from the drum or rotor. However, if the wheel seal is experiencing major leaking, then it is recommended to replace it right away.

• Air Systems: It is also important to make sure there is enough air pressure being produced for the whole braking system to work properly. Drivers should keep an eye out for any air compressor cycling occurring. When the air dryer discharges air, see how much water and/or oil is coming out of the purge valve. Also, be sure to drain the air tanks, any water that gets in the air tanks will take up essential air volume needed to make the air compressor cycle more.

In review, when doing a pre-trip check of a truck’s braking systems, drivers should make sure to check for any brake hoses with cracks or bulges present. Check the clevises and pins on the yokes of brake chambers, rusted brake chamber clamps, and that none of them are falling off their mounting brackets. Also, measure that all brake shoes are the correct thickness and do not need to be replaced. Check to see if the brake drums have a large lip or any heat flexural cracks, and that there is no oil on the brake drums. Adding these brake system checks into a regular pre-trip inspection will help increase the ability of the truck to deliver the shipment efficiently and get the driver and unit back safely.

WHAT DOES IT LOOK LIKE?

Brake Chambers: This is an example of a brake chamber clamp that is broken on the disc brake chamber.

S-Cam: Inspect the s-cam snap ring to make sure that is seated correctly to avoid separation or damage to slack adjuster and s-can or total brake application failure.

Brake Drums & Shoes: Inspect brake drums for cracks and brake shoes for the proper thickness.