Air Disc Brakes
Disc brakes have been around for over a century, but air disc brakes for heavy duty trucks and trailers have only started to become popular in recent years. This rise in popularity is mostly due to the new Federal Motor Vehicle Safety Standard 121 (FMVSS 121) which outlined requirements for reduced stopping distances on trucks and trailers. Air disc brakes have many advantages over traditional drum brakes, providing improved braking control and higher braking efficiencies although they do have the downside of a higher initial investment cost and increased maintenance costs.
As expected, an air disc brake setup has an entirely different appearance compared to a drum brake setup. It is not hard to tell the difference in the two designs as the components of air disc brakes are exposed with no brake drum to cover them. Air disc brake assemblies are more compact and far less complicated with no brake cams or external slack adjusters. A large vented disc sits at the middle of the air disc assembly with an air disc caliper wrapped around it. An air brake chamber is bolted directly to the caliper, with no exposed push rod the air disc caliper is directly actuated by the chamber and contains an internal adjustment mechanism instead of an external slack adjuster and brake cam.
Each component of the disc brake system is critical to the performance of the brake assembly and as soon as an issue is discovered the part should be replaced and the entire wheel end assembly checked.