How brake calipers work

Sometimes brake problems can be traced back to caliper problems. See how they work and learn about replacement options when they go bad. A brake caliper converts hydraulic pressure into mechanical force. This force is multiplied from the driver’s foot applying pressure to the brake pedal.

Picture of brake caliper

Therefore some driver complaints about the way the car stops or the way the brake pedal feels can actually be a problem with the calipers. Also a common front brake problem would be a hard and sometimes scary pulling condition where the car pulls to the left or right only when braking.

The caliper housing is usually a one-piece construction of cast iron or aluminum. The brake caliper housing contains a cylinder bore. Machined into the cylinder bore is a groove to allow a square cut seal to be seated. At the top of the cylinder bore will be another groove that allows for a dust boot to be installed.


A caliper can contain one to four cylinder bores and Pistons that provide uniform pressure distribution against the brake rotor through the friction pads. Standard disc brake caliper pistons are relatively large in diameter and short in stroke.

This provides high pressure force through the brake pads to the disc brake rotor. The disc brake caliper piston is usually made of steel or aluminum but on some Chrysler models you can find a composite resin piston that looks very much like plastic.

Replacing brake calipers

Picture of loaded caliper

When replacing brake calipers you will have a few choices available to you. These choices will apply if we are replacing either the front or the rear brake calipers. There is now a trend towards installing loaded calipers rather than overhauling the existing calipers. I agree with this trend and prefer to purchase new parts as opposed to remanufactured loaded calipers.

Now this is just my personal opinion but I find that the factory does a much better job than a remanufacturing company overall. Whether you select a new or remanufactured unit is up to you and in both cases they usually have some type of warranty if there is a problem.

The term loaded refers to the fact that new brake pads are included and installed. Most also include new hardware such as caliper slides and anti rattle clips. Basically a loaded caliper is ready to bolt on and can take some of the human error possibilities out of the equation.


Problems replacing brake calipers

Picture of worn brake pads

One of the major causes of premature brake pad wear is rust or corrosion. In the case of a floating caliper they are mounted to a steering knuckle or mounting bracket in the case of a rear caliper. When these parts are installed there is a small space between the bracket and the caliper.

This allows for the free movement and more importantly a full release of the brake component. This small space is known as an air gap. Even though loaded replacement calipers are ready to go this air gap should be checked after the installation of these parts. If corrosion and rust has built up and the caliper does not move freely it can cause accelerated brake pad wear as described above.

On my you fix cars site I have a complete repair module that explains in detail about the different components of car disc brakes. For more articles posted recently on this website visit the online auto repair blog. Or this next link will take you back to the Disc brake diagnosis page from this post about how brake calipers work.


2 comments

  1. Is there anything that causes the pads to move away from the disc when you take your foot off of the brake?
    I have a 2002 Honda van that has a growling noise coning from the brake. I have replaced the pads and lubricated the back side of the pads and the mating surfaces between the pads and the clips between the pads and the caliper. The pads seem to stay in contact with the disc when we take our foot off of the brake. I am thinking that something has to be in the design to pull the pds away from the disc.

  2. When you take your foot off the brake pedal the caliper stops applying the pads against the rotors. They really do not actually pull the pads away from the rotors. How we test for sticking calipers is to raise the vehicle and spin the wheels by hand. then apply and let go of the brake pedal the pads should fully release each wheel and no drag should be felt.
    Technically some would say it is the action of the caliper seals that pulls the piston back in its bore ever so slightly. BUT to answer your question on the 2001 Honda if the brakes are dragging the most common cause would be a binding caliper.
    But it could be other things. I remember years back GM had maladjusted brake switches holding down on the pedal slightly causing this condition.

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