An Audi's brake caliper contains pistons that press the brake pads against the rotor, creating the friction slows the wheel. Changing the brake pads on an Audi is a routine aspect of maintenance and requires that the caliper be removed from the rotor so the pads can be removed and new ones installed. However, the piston usually needs to be retracted into the caliper to allow enough clearance for the new, thicker pads and the caliper to slide over the rotor. On Audis and Volkswagens, the piston needs to be rotated as it is retracted.
- Skill level:
- Moderately Easy
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Things you need
- Caliper piston retracting tool
- Locking pliers (if no tool is available)
Clean the caliper and nearby areas with brake cleaner. If you are having to retract the caliper piston, that probably means you are installing new brake pads.
Remove the lid on the brake fluid reservoir and inspect the brake fluid level. If the level of the fluid is relatively low, proceed with retracting the caliper. However, if the fluid is right at the top, the pressure from pushing the piston into the caliper may cause the fluid to overflow. Remove some of the brake fluid with a turkey baster or large syringe if you do want the fluid to spill out. You can also simply put rags around the reservoir.
Support the brake caliper with something while you are retracting the piston so that it does not hang on the brake line and potentially damage it.
Slide a caliper piston retracting tool onto the slots in the caliper and turn the piston with the tool while pressing it into the caliper. You may need to use a C-clamp to tighten the piston into the caliper while simultaneously turning it. Retract the caliper until there is enough clearance between the pads and the rotor to slide the caliper over the rotor. You will have to stop and check this by temporarily installing the pads, since you cannot retract the piston with the pads installed.
Slide the caliper over the rotor once you have retracted the pistons enough. Tighten the caliper bolts. Top off the brake fluid and put the lid back on the reservoir.
Tips and warnings
- If you do not have access to the special caliper piston retracting tool, you can use large locking pliers and a rag to retract the pistons. Place the rag over the piston so the piston does not get scratched, then tighten the locking pliers onto the piston just enough to grip but not enough to scratch or damage it. Turn the piston and press it into the caliper.
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