Proper Air Brake Maintenance Reduces Downtime

Proper maintenance and operation of your truck's air brake system can dramatically reduce downtime.

May 19, 2011

Remove all pressure from the air system before you disconnect any component, and park the vehicle on a level surface.

Air brake systems are made up of many separate parts, all of which must be in good condition to provide reliable operation. Inspections catch problems early. In addition to visual driver inspections, technician inspections are important and should be performed on a regular basis," says Joe Kay, chief engineer of brake systems, Meritor. "During these more thorough inspections, technicians should check linings for wear, cracks and fractures."

Check air break systems for:

Check for valve failure in primary or secondary circuit. These failures can compromise the system. To check, open the drain valve on the wet tank.
Look for accelerated wear. Check for dirt and debris between the lining and braking surface as well as on rubber boots and seals.
Fractures and leaks.
Proper operation of the push rods and slack adjusters. This is essential to maintain the position of the brake shoes relative to the drum.
Check push rod actuation out of the brake chambers. Look for broken or weak springs.
Check slack adjusters for broken or missing parts.
Inspect brake lining for cracked, broken lining blocks, uneven wear on an axle, and make sure there is no scoring and the drums are not out of round.
Don't forget to check the parking brake daily for leaks in each chamber or broken or damaged components.

If the air brake system needs repair, choose the repair parts wisely.

Consider differences in the friction materials
Make sure performance meets or exceeds the OEM brake linings

Learn more about the importance of proper maintenance on an air brake system in the article "Don't Let Your Brakes Fail You," which appears in the June 2011 issue of Equipment Today.

Are Disc Brakes the Future?

Air disc brakes are being adopted for many on-highway applications. This is a technology to watch for future severe service applications.

“Today’s air disc brake systems have been limited to line haul and pick-up and delivery — 100% on-highway applications — until the OEMs have enough field experience with the air disc to understand the impact vocational applications have on component wear,” says Thomas Macmenemy, engineering manager, Daimler Trucks North America.

“Meritor has seen an increase in the use of disc brakes in such applications as fire, military and bus,” says Joe Kay, director, brake engineering, Meritor. “Refuse applications have also seen a benefit in the extended lining life offered by disc brakes.

"Vehicles that spend more time in off-road applications need to be more cognizant of brake cleanliness," he continues. "Drum brakes by design are more sheltered from dirt and debris. The rotors of the disc brake system are more exposed and likely to see buildup of mud and contaminants.”

Understand Proper Operation

It's important to understand that all brakes build up heat during use due to friction. However, excessive use of the brakes when descending a grade creates excessive heat. This causes a loss of braking power known as brake fade.

Long downhill runs can wreak havoc on a brake system if the driver doesn’t understand proper braking technique. Avoid continuous application of the brakes in these circumstances. This creates heat buildup, which causes the brake drum to expand. The shoes have to travel farther and the brakes eventually fade. The proper technique for braking on long grades is intermittent application, known as snubbing.