How to Fill Calipers on a Mountain Bike

The brakes on your mountain bike need to be maintained and serviced much like the brakes on your car. At least once a year, you should bleed and fill the calipers on your mountain bike to keep the brakes in good working order. It does not matter what brand of brakes you have, the process is the same. Take an afternoon and service your mountain bike completely -- it will keep you going longer.

Things You'll Need

  • Metric box wrench set
  • Plastic tube
  • Empty jar
  • Automotive syringe
  • Brake fluid -- DOT 3/4
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Instructions

    • 1

      Remove the wheels from your mountain bike.

    • 2

      Remove the brake pads from each set of brakes. Depending on the model of brake, you may have to use a small box wrench to unscrew the pad frame, or you may need to bend the metal tabs holding the pads in place to remove them.

    • 3

      Unscrew the retaining nut holding the caliper to the frame and remove the caliper.

    • 4

      Attach a plastic hose over the brake bleed screw, located in the brake handle. Put the free end of the hose in an empty jar. Loosen the bleed screw with a open box wrench and press the brake handle several times, till all the fluid has been bled from the system. Close the bleed screw when done.

    • 5

      Fill an automotive syringe with DOT 3/4 brake fluid. Remove the plastic tubing from the jar and attach it to the syringe so the syringe and bleed screw are now connected. Press down on the syringe plunger to push the brake fluid into the tube and force any air out.

    • 6

      Press the piston back into the caliper and hold it in place.

    • 7

      Open the bleed screw and fill the caliper by depressing the plunger on the syringe. When you have added the recommended amount of fluid for your brake system, close the bleed screw, release the piston and remove the plastic tube. Reinstall the brake caliper to the frame. Reinstall the brake pads and wheel and move on to the other brake.