Air Disc Brakes

Air Disc Brakes

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SKU L44649
$5.75

Precision 1-1/16 inch inner diameter tapered bearing is designed for high-speed use and built to ori...   Details

20+ In Stock
  • Inside Diameter:1-1/16 inch
  • Outside Diameter:1.980 inch
  • MPN: L44649
SKU L68149
$6.15

Precision 1-3/8 inch inner diameter tapered bearing is designed for high-speed use and built to orig...   Details

20+ In Stock
  • Inside Diameter:1-3/8 inch
  • Outside Diameter:2.3612 inch
  • MPN: L68149
SKU 14125A
$9.16

Precision 1-1/4 inch inner diameter tapered bearing is designed for high-speed use and built to orig...   Details

1 In Stock
  • Inside Diameter:1-1/4 inch
  • Outside Diameter:2.7148 inch
  • MPN: 14125A
SKU 15123
$5.42

Precision 1-1/4 inch inner diameter tapered bearing is designed for high-speed use and built to orig...   Details

20+ In Stock
  • Inside Diameter:1-1/4 inch
  • Outside Diameter:2.4409 inch
  • MPN: 15123
SKU 25580
$10.90

Precision 1-3/4 inch inner diameter tapered bearing is designed for high-speed use and built to orig...   Details

3 In Stock
  • Inside Diameter:1-3/4 inch
  • Outside Diameter:3.265 inch
  • Freightliner Number:SBN 25580SKF
  • Meritor Number:25580
  • Navistar Number:TM25580
  • Paccar Number:25580TRB
  • Timken Number:25580
  • Volvo Number:TDA25580
  • MPN: 25580
SKU LM67048
$5.56

Precision 1-1/4 inch inner diameter tapered bearing is designed for high-speed use and built to orig...   Details

20+ In Stock
  • Inside Diameter:1-1/4 inch
  • Outside Diameter:2.328 inch
  • Dexter Number:031-032-02
  • Euclid Number:E-TMLM67048, ETMLM67048
  • Meritor Number:LM67048
  • Redneck Number:LM67048
  • Timken Number:LM67048
  • MPN: LM67048
SKU 182.687
$39.04

Wheel bearing cone 182.687. 3.990 inch inner diameter, 1.675 inch length.   Details

4 In Stock
  • Length:1.675 inches
  • Inside Diameter:3.990 inches
  • Caterpillar Number:4B8395
  • Chevrolet / GM Number:107535, 109180, 144489, 941261, 9412658, 9412661
  • Dana Number:550846
  • Eaton Number:6600776
  • International Number:0292037R91
  • Mack Number:62AX217
  • Navistar Number:292037R91, BWR687, TM687
  • Paccar Number:687TRB
  • Spicer Number: 550846
  • Timken Number:687
  • UPC: 889626047473
  • MPN: 182.687
SKU 182.HM518410
$11.84

Wheel bearing cup 182.HM518410. 6.000 inch outer diameter, 1.188 inch width.   Details

2 In Stock
  • Length:1.188 inches
  • Outside Diameter:6.000 inches
  • Federal Mogul NumberHM518410
  • Timken Number:HM518410
  • UPC: 889626047718
  • MPN: 182.HM518410
SKU L44643
$3.88

Precision 1 inch inner diameter tapered bearing is designed for high-speed use and built to original...   Details

20+ In Stock
  • Inside Diameter:1 inch
  • Outside Diameter:1.980 inch
  • MPN: L44643

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.

Air Disc Brake Chambers

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.


Air disc calipers

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.


Air disc rotors

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.


Air disc 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

    Reduced stopping distances – The modern design of air disc brakes offer shorter stopping distances and greater brake control. Brake fade is less of an issue because as the rotor is heated, it expands and is closer to the pads. On a drum brake, the drum expands away from the brake shoes increasing the distance the shoes need to travel to apply. The lower mass of an air disc rotor allows it to shed heat easier than a drum.
    Extended service intervals – Air disc systems are designed to go more miles between service than drum brake systems. In long haul situations, rotors are designed to last 750,000 – 1,000,000 miles and pads will last up to 500,000 miles.
    Simple design – Fewer components are involved with a disc brake system, this lowers the weight of the wheel end and simplifies service and inspections of the brake system.
    Less downtime - According to Bendix, a technician can perform four wheels of disc pad changes in the time it would take to change one set of drum brake shoes. The design of air disc brake assemblies allows pad changes from the outside of the caliper without removal of the caliper itself. After the pads are removed the caliper tappets and carrier can be checked for excess movement as well as the rotor checked for thickness and runout. If everything is within spec new pads can be installed, and you are on to the next wheel.

Disadvantages of air disc brakes

    Higher initial cost – Outfitting a truck or trailer with air disc brakes will generally be 30% - 40% more expensive than drum brakes. This cost can add up on an 8-axle trailer!
    Greater heat generation – Due to the smaller friction area of the pads and rotor the heat generation is much higher on a disc brake. These assemblies are designed with this heat in mind, but greater attention should be paid to the wheel end assembly as the wheel seals and bearings will also be subjected to this greater heat.
    Lack of universality- Each air disc brake system has parts that are specific to its setup, calipers, pads, and rotors are not interchangeable and with a lower percentage of current vehicles running air disc brakes service parts may be harder to find.

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.


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