How to Adjust a Caliper Piston

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What You'll Need
Needle Nosed Pliers
Lug Wrench
WD40 or Penetrating Oil

When you are changing your brake pads, you will inevitably have to adjust your caliper piston to make way for the new pads. These will be thicker than the older ones, due to them being worn down by extensive use.

Step 1 – Wheels

Using the lug wrench that goes with your vehicle, undo the lug nuts on the wheels before you raise the car off the ground. Just crack the lug nuts until they are loose enough that you can spin the 4-way wrench.

Step 2 – Raise the Car

Jack the car up using the jack that came with the vehicle. If that is not available, use a hydraulic jack. Place blocks behind the back wheels of the vehicle to prevent the car from slipping back. Apply the handbrake or emergency brake to make sure it stays in place. Use jack stands to safely support vehicle. Take careful precautions to ensure your safety and the safety of anyone who may be helping you.

Step 3 - Remove the Wheels

Now the car is raised safely, you can remove the wheels from the front of the vehicle. The lug nuts will easily remove, since you cracked them earlier.

Keep the lug nuts safe inside the wheel and place it away from your work area.

Step 4 - Removing the Brake Pads

Now you will need to remove the brake pads to access the brake caliper pistons.

Using needle nosed pliers, remove the retaining clip from the pads and slide them out. They will need to be persuaded a little so use a flat head screw driver to pry them out if they offer resistance.

Step 5 – The Caliper

Once the brakes have been removed from the housing, you will notice a round plate inside the caliper. This is the caliper piston and this will adjust itself naturally as the brake pads wear down. It will push up slowly for every millimeter that the brake pads reduce by and clamp itself in line with the movement of the brake wear to compensate.

Step 6 – The Piston

Since the new pads that you are installing will be considerably wider than the old ones, you will need to adjust the caliper piston and reset it back down to its original seating place so that the new brake pads will fit snugly into the calipers.

Step 7 – Adjusting the Piston

Take a C-clamp and open it to fit around the caliper and touch the piston. Very slowly, turn the C-clamp screw and tighten the c-clamp until the piston has reverted back to the original position. This action also pushes all the brake fluid back up the brake lines and into the master cylinder. Tighten the c-clamp until it will not move any further. This indicates that the piston is placed correctly. Now, you can remove the c-clamp.

Now that your piston has been correctly adjusted you can go ahead with replacing the new brake pads into the caliper. Be sure to depress brake pedal firmly several times to set the piston again.