What does the brake caliper do?

Brake calipers can be variously categorized according to their structure and power source.

When it comes to the structure of brake calipers, they can be divided into two types, floating and fixed. A fixed brake caliper does not move relative to the disc and is hence more vulnerable to disc imperfections. It adopts one or more pairs of opposing pistons to clamp from each side of the disc, and is more sophisticated and costly than a floating brake caliper.

Floating Brake Caliper

A floating brake caliper moves with respect to the disc, along a line parallel to the axis of rotation of the disc; a piston on one side of the disc pushes the inner brake pad until it makes contact with the braking surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc. However, floating caliper designs with a single piston are vulnerable to sticking failure because of dirt or corrosion entering at least one mounting mechanism and stopping its normal movement. This can lead to the brake caliper’s pads rubbing on the disc when the brake is not engaged or engaged at an angle. Sticking can be a result of infrequent vehicle use, failure of a seal or rubber protection boot allowing debris entry, dry-out of the grease in the mounting mechanism and subsequent moisture incursion leading to corrosion, or any combination of these factors. Consequences can include reduced fuel efficiency, excessive heating of the disc or excessive wear on the affected pad. A sticking front caliper may also cause steering vibration.

Swinging brake caliper

Another type of floating caliper is a swinging brake caliper. Unlike a pair of horizontal bolts that enable the caliper to move straight in and out respective to the car body, a swinging brake caliper uses a single, vertical pivot bolt located somewhere behind the axle centerline. When the driver presses the brakes, the brake piston pushes on the inboard piston and rotates the whole caliper inward, when viewed from the top. Because the angle of the swinging caliper’s piston changes relative to the disc, this design uses wedge-shaped pads narrower in the rear on the outside and narrower on the front on the inside.

When it comes to power source that pushes the piston, brake calipers fall into hydraulic type and pneumatic type. The former uses brake fluid to push the pistons while the latter works with air pressure. Pneumatic brake calipers are more widely used when the requirements for power and pressures are not that demanding, whereas hydraulic brake calipers are used where greater amounts of power and pressure are required. Both of these two types have their own distinct advantages, some of which have been detailed in the following chart.