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The Viair 92155 safety valve is rated to 155 PSI and is designed as a replacement for small air comp... Details
The Viair 92145 safety valve is rated to 145 PSI and is designed as a replacement for small air comp... Details
The Viair 92175 safety valve is rated to 175 PSI and is designed as a replacement for small air comp... Details
The Viair 92205 safety valve is rated to 205 PSI and is designed as a replacement for small air comp... Details
The Viair 92250 safety valve is rated to 250 PSI and is designed as a replacement for small air comp... Details
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.
Convert air system pressure into mechanical movement. The air disc chamber may be a service type which only applies the service brakes, or it may be a spring brake which will apply service brakes and act as a parking brake. Air disc chambers have a short, rounded pushrod that is not threaded like a drum brake chamber. There is no clevis or slack adjuster, and instead, an air disc chamber acts directly on the air disc caliper. Air disc chambers are susceptible to the same issues as traditional drum brake chambers as the internal components are the same. This means that diaphragms or brake springs can fail and require replacement, sometimes leading to the replacement of the entire assembly.
are the most complicated part of an air disc brake system but most of its components are internal and not serviceable. The air disc caliper contains a lever and pivot point that provides increased application force through mechanical leverage. This is the same principle used on a drum brake system with the slack adjuster and the brake chamber pushrod. The air disc chamber applies force to the lever, and this pushes out a piston or two pistons that apply this amplified force to the brake pads. The air disc caliper contains a slack adjustment mechanism that turns the threaded pistons to compensate for pad wear and prevent delays in brake application. Some air disc brake systems will have a built-in wear indicator that will visually show the amount of pad wear with some even having options for electronic warnings to be triggered on the dash of the truck. External adjustment of the brake caliper is necessary after servicing the system and due to the sensitive nature of the adjustment meninism and the high cost of replacing the caliper the brake system manufacturer will use torque limiting device to prevent damage. This is generally in the form of a replaceable break-away adjuster that will shear if too much torque is applied.
have a large variety of designs to accommodate different hub and axle requirements. Along with the air disc pads, the rotor is a wear item that will need to be replaced over time. In ideal conditions, an air disc rotor should last multiple pad changes before it reaches its minimum thickness and needs to be replaced. During pad changes, the rotor is checked for runout or warping, which can occur from excess heat or quenching when a hot rotor is rapidly cooled by splashes of water. If the rotor is within the manufacturer spec it can continue to be used through several sets of pads.
are the main wear item on the air disc brake system. The pads provide the friction necessary to convert the energy of motion into heat. Due to the comparably small size of air disc pads versus drum brake shoes the pressure and temperature that air disc pads are subjected to is very high. Air disc pads have an extended service life over that of a drum brake setup as the design of the calipers prevents the pads from dragging and speeds up brake release times.
Air disc brakes are quickly becoming the new standard. Current drum brakes are being pushed to the limit to meet the shorter stopping distance requirements that are being introduced by the government and air disc brakes are meeting these requirements with ease. Despite the increased stopping distance, air disc brakes have both advantages and disadvantages over drum brakes.
Advantages of air disc brakes
Disadvantages of air disc brakes
As time goes on air disc brakes will become more common and eventually they will become the standard for heavy-duty brakes. Increasingly, new trucks and trailers are being built with air disc and as more hit the road the demand for replacement parts will increase. At TruckSpring.com we carry replacement pads, rotors, chambers, and calipers for the most common systems currently in use. We also have the knowledge to help you identify and order the correct replacement air disc components. If you need help finding parts for your air disc setup give us a call at 1-800-358-4751 or email us at Truckspring@truckspring.com, and we will be glad to help find replacement parts you need to get your truck back on the road.