What Is a Foundation Brake?

by Meghan JonesUpdated August 09, 2022

Foundation brakes are components inside a truck wheel which encompass many smaller parts of the brake system.

Foundation Brake Composition

Foundation brakes can be found at the end of each axle. The foundation brakes are made up of several components including the spring actuator, the brake drum, and the mechanical brake mechanism, which includes the brake shoes and friction material.

Foundation Brake Parts include:

  • The Spring Actuator
  • The Brake Drum
  • The Mechanical Brake Mechanism
  • The Brake Shoes
  • And, the Friction Material

Foundation Brake Types

Foundation brakes are found in vehicles with air brakes, such as large trucks. There are three foundation brake types: ā€œSā€ cam brakes, wedge brakes, and disc brakes. And a fourth obsolete type called the air over hydraulic brake.

  • The "S" cam drum brake is the most popular kind of foundation brake for air brakes.
  • Wedge and the Air Over Hydraulic brake are obsolete
  • Disc brakes are where brake pads pinch the rotor, a circular steel plate, creating friction which slows the vehicle. Disc brakes do not experience brake fade like the drum brake.

Attempting Maintenance on a Foundation Brake?

Brake maintenance is vital to proper vehicle function and driver safety. While the adjustments made to a brake system and foundation brakes are best left to professional mechanics, it is the driver's responsibility to ensure this maintenance is given priority; if the foundation brakes are not in working order, the rest of the brake system will not function.

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