The wedge brake chamber is a type of air-operated drum brake that uses a push rod to push a wedge between two brake shoes, forcing them out against the inside of a drum. This type of drum brake is often used in heavy trucks, where it generates high braking force.

Foundation Brakes
There are three main types of foundation brakes: "S" cam brakes, disc brakes and wedge brakes. Each system relies on a different set of parts to produce braking power.


“S” cam brakes (also called slack adjuster-operated air brakes) use a slack adjuster attached to the end of a camshaft. The stroke of the pushrod acts on the slack adjuster and causes the camshaft to rotate.

A “S” cam brake can be either self-adjusting or manual adjusting. Self-adjusting brakes allow the brakes to self-adjust to maintain a consistent brake pressure across the entire range of wheel speeds.

Disc Brakes
Air-operated disc brakes use a chamber and a slack adjuster like s-cam brakes, but instead of using an S-cam, they use a "power screw." The pressure of the chamber on the slack adjuster turns the power screw which clamps the disc or rotor between the brake lining pads of a caliper. This type of brake is less common than s-cam brakes, but they are more durable and require less maintenance.

To determine if the brakes need adjustment, make a mark where the pushrod exits the brake chamber and hold a full brake application. If the difference between the marks is more than 1-1/2 inches, the brakes need adjustment.