Compressing a brake caliper is always necessary when replacing the disc pads, because as the pads wear, the piston extends. It’s an automatic self-adjusting system by default.
If when you’re replacing the brakes you find that one caliper won’t compress (this doesn’t usually happen to both of the calipers at once), you need to replace the caliper anyway. Note that rear brake calipers that have integrated park brakes take special tools. We’ll talk more about that later.
Dealing with a brake caliper that won’t compress can be quite troublesome. It’s the one thing that drivers hope will never happen to them, especially when driving fast on a freeway.
So why does this happen?
Brake caliper pistons can be compressed in several ways. While using compression tools like a C-clamp or channel lock is the easiest way to do the job, you can get around the task without it.
Before anything else, make sure that you’re wearing gloves and other safety equipment to prevent any injuries.
Proceed with loosening the wheel bolts or nuts and raising the vehicle using jack stands.
Next, remove the wheel and unbolt the caliper. Make sure the caliper isn’t hanging freely to avoid damaging the brake lines. Use wire ties or wire to support the weight of the caliper.
Once that’s out of the way, you can open the cap on the brake fluid reservoir.
Use one of your old brake pads between the tool tip and the pistons since some calipers have dual pistons. This will enable the tool to press the pistons back into the caliper evenly.
Use a large flathead screwdriver or a pry bar and before you unbolt the caliper, slowly apply force between the pad and the rotor (you’ll need start at the edge where the pad ears are) and hold steady pressure so that the caliper piston retracts. If you are able to fully compress the piston this way, you probably won’t need to use the tool, but have one ready anyway or a C-clamp.
Note: Most rear parking brakes now are either electric or have a small set of brake shoes that work inside a “hat” type disc rotor, so this tool won’t be used on those.
When using a brake caliper wind back tool on an integrated park brake caliper, choose a circular plate that interfaces with the caliper’s piston grooves. Read the instructions that come with the tool to learn how to use it properly.
There are generally three types of brake caliper designs一fixed, floating, and sliding.
A fixed brake caliper is mounted to the suspension, hence its name. This type uses two, four, or six pistons to apply the brake pads.
One advantage a fixed brake caliper has over other designs is its size and weight. A large and heavy caliper like this is great at absorbing and dissipating great amounts of heat and lets the rotor and pads run cooler.
However, a fixed brake caliper has multiple pistons and split bodies, which means servicing one can be quite complicated.
A floating caliper design isn’t mounted to the suspension. For this design, the caliper can move within a limited range on an anchor plate that’s mounted to the suspension.
Compared to a fixed caliper, a floating brake caliper has a simpler construction, lower cost, and compact size. However, the flexibility of a floating caliper can contribute to a spongy brake pedal.
The flex also causes the caliper body to twist slightly when the brakes are applied, resulting in tapered wear of the brake pad lining material.
The body of a sliding brake caliper is directly mounted to the anchor plate. Instead of using pins and bushings, a sliding caliper moves on ways cast and is machined into the caliper and anchor plate.
A sliding caliper has the same advantages and disadvantages as a floating caliper.
Maintaining and cleaning your brake calipers are key if you want to reduce the risk of your caliper pistons getting stuck.
Cleaning the brake caliper can also extend its lifespan and maximize your vehicle’s braking efficiency.
When cleaning your brake calipers, make sure to use a cleaner that’s intended for brake parts. This will help break down the dust and grime without damaging the hardware.
Once you’re done cleaning and wiping the brake caliper dry, it’s also a good idea to apply a protective coating or caliper paint. This enhances the caliper’s appearance and forms a layer that protects it from dirt and grime.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.