How to Compress Caliper Piston – 4 Best Ways to Do It Right!

Every enthusiastic car owner should know how to compress caliper piston. When brake pads become too old or faulty, they require immediate replacement.

Replacing brake pads can be a bit technical for some people. One has to compress brake calipers in a particular way using unique tools.

Even when not using special tools, you have to be more careful. For instance, a screwdriver adds imbalanced forces to the piston and can get it stuck during compression.

A screwdriver is also not the best tool to compress a plastic piston because it can damage it.

First, lift the hydraulic reservoir lid to minimize pressure build-up.

Also, open the bleeder valve and keep a can or pan beneath the car to gather the liquid. We want to help you compress your brake caliper piston correctly via this guide.

How to Compress Caliper Piston: 4 Individual Methods

To replace old brake pads, you need to gradually compress the brake caliper pistons until they slide into their original housing.

There are different ways to do the compression process; choose the easiest. All techniques are effective, and we will discuss them next.

Method 1: C-clamp

If you want to compress the brake caliper piston using C-clamp, do these steps:

  • Step 1: Position the C-clamp

Align the c-clamp at a stable position over the brake caliper. Next, ensure that its end pushes against the brake caliper piston.

Ensure the brake pad rests in front of the piston and between the C-clamp jaws.

  • Step 2:Rotate the screw 

Next, turn the screw without applying excess force.

  • Step 3: Protect the brake pad from the clamp jaws

Place a chunky wood between the c-clamp and the piston to keep the jaws from drilling a hole into the brake pad.

  • Step 4: Tighten the c-clamp

Next, fasten the c-clamp to compress the piston inward.

  • Step 5: Make adjustment

Continue to adjust and tighten the c-clamp until it gets easier to install the new brake pad on top of the caliper.

Method 2: Channel Locks Pliers

In the prior method, we used the c-clamp. Here we will use a pair of channel locks pliers. Steps include:

  • Step 1: Remove the caliper

Unfasten the brake caliper and remove the bolt.

  • Step 2: Position the Brake pad

Next, put the brake pad in front of the piston. Ensure that it fits well. After that, adjust your channel lock position.

  • Step 3: Align the channel lock

Place one side of the channel lock behind the brake caliper and the other end behind the brake pad. In short, ensure that the brake pad and caliper are between the grips.

  • Step 4: Compress the channel lock

Use maximum force to compress the channel lock so that the piston retracts inward.

Method 3: Compressor tool

An alternative way to compress the caliper piston is to use a compressor tool. Here are the steps to do:

  • Step 1: Remove the caliper

Detach the caliper from the bolts.

  • Step 2: Align the brake pad 

Put the brake pad at the front of the brake caliper and piston.

  • Step 3: Insert the compressor tool in the caliper

First, adjust the caliper compressor and push bar. Then, put the caliper compressor inside the caliper in front of the brake pad.

  • Step 4: Pump down the compressor 

After ensuring that the brake pads are well-positioned, use the compressor tool.

The push bar will ram out against the brake pad. As a result, the brake pads will press against the piston. Eventually, the piston will pull inwards

Method 4: Use a screwdriver

If you do not have a c-clamp, channel lock, or compressor tool, use a screwdriver.

Do these steps:

  • Step 1: Use a screwdriver inside the caliper window

Place your screwdriver inside the brake caliper window and hold it firmly. At the same time, move it inward between the openings.

Plunge the screwdriver to a depth where you can equalize force to pull in the piston.

  • Step 2: Apply outward force

Now you are ready to pull your screwdriver outward tightly against the brake pad.

  • Step 3: Reposition the screwdriver

Put your screwdriver amid your brake caliper and brake pad. Locate the piston head with it.

  • Step 4: Compress the piston

Gently and tightly push the piston head with your screwdriver to ensure the piston rests where it should.

Brake Caliper Piston: What & Why?

Brake caliper pistons cause the brake pads and brake discs to contact. Once they do, the car slows down.

When you press the brake pedal with your foot, the action forces the brake fluid to flow from the master cylinder to the brake pipes before entering the brake caliper.

After that, the fluid pushes the pistons outs at the back of the brake pads. Then, the pressure causes the brake pads to touch the discs.

After releasing the foot from the pedal, the brake pads retract. Then, the piston will close. Floating brake calipers consist of one or two pistons with a huge diameter.

In contrast, fixed calipers have pistons with a small diameter. There are pistons on both sides of the rotor that provide the braking force.

Also, brake caliper pistons can feature steel, aluminum, or phenolic construction materials. Metal pistons are sturdy but also prone to corrosion.

Types of the brake caliper piston

Different kinds of brake caliper pistons exist. Regardless, the process of compressing them is virtually similar.

Below are the different types of cars:

  • Floating brake calipers – A floating caliper features a piston on one side of the rotor. When you press the brake pedal, this piston presses on the brake pad on the rotor’s inboard side. Next, the caliper slithers over the bushings or pins and pushes the outboard pad against the rotor. Due to this, the braking process works. 
  • Fixed brake calipers – A fixed caliper can have two, four, six, or eight pistons. It has the same number of pistons on the inboard and outboard sides of the rotor. Attached to a bracket without sliding bushings or pins, a fixed brake caliper is the most prevalent and costly type around. 
  • Sliding brake caliper – A sliding caliper looks like a disc, and it fits in the slot within the caliper adapter. When the piston exerts pressure on the brake pad, the sliding caliper triggers the braking action.
  • Higher performance calipers – These offer more clamping area and force due to having oversized pistons. They also offer six to twelve pistons.

How To Free A Stuck Brake Caliper Piston: 3 Steps Methods

After leaving your car in the garage for too long, its brake calipers may rust due to lack of lubrication. If calipers rust, they do not compress.

Another cause of this is dry caliper bolts. If the shielding rubber layer tears down, the lubricant may seep out, which can dry out the bolts.

If you have a long pushrod than necessary, it can cause the brake caliper to stick. When the piston rubber tears down, the piston will lose its lubrication and enable rust to form.

We will teach you how to release it next.

Step 1: Check the surrounding parts

Take the time to inspect every component near the stuck calipers to see if they have also shifted to the wrong position.

Step 2: unfasten the bleed valve

It is necessary to bleed the fluid before you release the stuck caliper piston. After opening the bleed valve, expel the brake fluid using gravity, vacuum, or pressure forces. Next, add new fluid and fasten the bleed valve.

Step 3: Inspect the pushrod

When the pushrod is too long, it can free the caliper. So, remove the rod and adjust its length by cutting. Alternatively, get a normal length pushrod.

General method

Step 1: Lift your car

After parking your car on a level surface, jack it up to lift it on the stand.

Step 2: Remove the wheel

Unfasten a wheel near the stuck caliper with your lug wrench.

Step 3: Remove the stuck caliper

Use your socket set to take out the frozen brake caliper from the bracket.

Step 4: Get rid of debris, lubricant, and dust

Clean your brake caliper to remove whatever made it freeze. Use a brake cleaner and a piece of cloth.

How to Compress Caliper Piston: 4 Ways

Common FAQs About How to Compress Caliper Piston

Can you compress a brake caliper piston?

Yes, you can compress a brake caliper piston using four methods. First, you can use a C-clamp and the steps we enumerated above.

If you do not have it, use a channel lock or a compressor tool.

What can I use to compress the brake caliper?

Experts would recommend the use of special tools, including a C-clamp, compressor tool, or channel lock. If you do not have these tools, use your screwdriver.

Do I need to open the bleeder valve to compress the piston?

Yes, you need to open the bleeder valve to let out the old brake fluid. Keep an old saucepan or tin to correct this brake fluid.

After draining it, fill the system afresh and close the valve.

Remember to point the bleeder valve upward without spinning the caliper to prevent a gush of air from entering the braking system.

Do you need to bleed brakes after compressing the piston?

No, you do not need to bleed the brakes when you finish compressing the brake caliper piston. Doing so would drain the fresh brake fluid you have added above.

Can you compress the brake piston without bleeding?

No, mostly you have to bleed the valves before compressing the piston.

Why can’t I push the caliper piston back?

If you cannot push it, the odds are that it is stuck due to corrosion or torn components. The best thing is to stop compressing it and instead try to unfreeze it.

We have explained the whole process above.

What happens if you don’t compress calipers?

It will be harder to install new brake pads when your current ones are of no use to you. The fully extended brake caliper will get on your way.

Why won’t my brakes build up pressure?

Such a problem can happen if you do not have adequate brake fluid. Also, if you have not inspected your fluid for a long time, it might have become too thin.

When there is damage to the disc brake caliper, your pedal will feel as soft as a sponge. Spongy brakes can be dangerous and you know why.

Can you use an AC clamp to compress the brake caliper?

Experts recommend using a C-clamp to compress your brake caliper. Simply place the clamp on the piston and push it gently back into its housing.

If your caliper needs screwing, do not thrust it in.

How do you compress the rear brake caliper piston?

Use a large C-clamp or an oversized pair of channel locks to compress your rear brake caliper piston.

Make sure you adjust the tool you are using to concentrate the force at the center of the piston.

How do I remove a caliper piston without compressed air?

Simply jack up the car’s front suspension and unfasten the wheels. Next, remove your brake pads from both sides and place a block of wood or cardboard to protect your rotors.

Press the brake pedal strongly until the pistons move to the rotor. Pull them out with your hand when they protrude out of the caliper body.

Should you grease brake pistons?

No, there is no need to grease your brake pistons unless you want to replace the brake pads.


Learning how to compress caliper piston is crucial if you to do your car repairs. As you have noted, the process is easy if you have the right tools.

Even without tools, you can use your screwdriver as long as you are cautious.

If you cannot compress your piston because of frozen calipers, you only need to do easy steps to unlock them.

Each process you need to do to compress or remove a stuck caliper requires a lot of caution.

If you cannot do this work, shift the responsibility to a professional mechanic.

Also, if you have a plastic piston, it would be better to have a special tool or else take the car to a mechanic.

As you correct one problem, ensure you do not create another by breaking your plastic piston or brake pad.

Take all the necessary steps to prepare for the compression process.