Brake calipers provide the mechanical action that allows disc brakes to function. While your brake pads and rotors physically create friction, they rely on the caliper pistons to push them into contact with one another. While brake calipers don't require attention as part of a routine maintenance plan, they can occasionally fail.

Since calipers are critical parts of your braking system, it's crucial to understand why they sometimes fail and your options for getting yours functioning again.

How Do Brake Calipers Work?

Brake calipers are fairly straightforward mechanical components despite their importance to your braking system. The typical brake caliper is essentially a metal housing for the brake piston. The caliper also usually has a bracket on its outboard side that holds the outer brake pad in place. When you press on the brake pedal, hydraulic fluid extends the piston and pushes the pads against your rotor.

Calipers generally only have a few moving parts. Aside from the housing and piston, two slide pins hold the caliper in place and allow it to move forward and backward as the piston extends and retracts. Dust boots protect the slide pins and their lubrication from contamination, and similar seals keep dust away from the piston and prevent brake fluid leaks.

Calipers may seem like an unlikely source of trouble with so few moving parts. Unfortunately, there are several ways that calipers can fail and reduce your braking performance or cause other significant problems.

How Do Calipers Fail?

Caliper failures almost always begin with the seals and dust boots. If moisture or debris enters the caliper, they can cause the piston to rust or cause the internal seal to wear down. Any rust on the piston can become a serious issue since it will create rust and prevent the caliper from smoothly extending or retracting. The piston seal can also fail and create a brake fluid leak.

Calipers also sometimes fail as a result of poor brake maintenance. Worn brake pads can increase heat and reduce thermal protection for the calipers. These more extreme heating cycles will cause the dust boot and seal to break down, leading to internal contamination, rust, and, eventually, caliper failure.

What Can You Do?

If your calipers are sticking, you'll need a qualified brake technician to examine the affected wheel and attempt to determine the problem. If the piston is still in relatively good shape, you may be able to repair the affected caliper using a rebuild kit. These kits typically replace the "soft" components such as seals, dust covers, and dust boots.

Unfortunately, replacing a piston is usually more trouble than it's worth. If your pistons are rusting or there's internal damage to the caliper, you'll need to install a new one to get your brake system working correctly again. 

For more information, contact a brake repair shop near you.