What wrench do you need to remove a brake caliper?
The tool you need depends on whether you’re working on a bicycle or a car. For most bicycles, caliper removal hinges on hex or Torx bolts; for cars, you’ll typically need a socket or wrench for the caliper mounting bolts and a flare-nut wrench for the brake line.
Bicycle brake calipers
Most bicycle brake calipers are removed by taking out two mounting bolts that attach the caliper to the frame or brake mount. The head type and size vary by brand and model.
Common bolt head types you may encounter:
- 4 mm Allen key (4 mm hex) for many Shimano and other brands
- 5 mm Allen key (5 mm hex) for many other models
- Torx (often T25 or T30) on a minority of models
When removing, keep track of any washers or spacers and ensure you don’t pinch or damage the brake pistons. Reassembly should follow the manufacturer’s torque specs to avoid caliper misalignment or leakage.
In practice, carrying a small multi-tool with both 4/5 mm Allen keys and a Torx bit is usually sufficient for most common road, mountain, and hybrid bikes.
Automotive brake calipers
Car brake caliper removal typically involves two steps: removing the caliper mounting bolts and, if you’re detaching the brake line, loosening the banjo bolt with a flare-nut wrench. The exact sizes vary by vehicle, so consult the service manual for your model.
- Caliper mounting bolts: commonly around 14 mm, but some vehicles use 13 mm or 15 mm bolts. Always verify with the repair guide for your car.
- Brake line banjo/flair-fitting: use a flare-nut wrench sized to the brake line fitting (often 10–12 mm across flats) to avoid rounding the nut.
For some jobs, you may also need tools to compress the caliper piston back into place when reassembling, and you should use proper safety precautions to avoid brake fluid exposure or system contamination.
Summary
In short, the wrench you need depends on the system. Bicycle calipers typically rely on 4–5 mm Allen keys or Torx, depending on the model. Automotive calipers usually require a 14 mm socket or wrench for the mounting bolts and a flare-nut wrench for the brake line, with sizes varying by vehicle. Always check the specific service manual or guidance for your exact make, model, and brake system before starting work.
