How to Troubleshoot Hydraulic Mountain Bike Brakes

Once solely used for motorcycles, hydraulic brakes are now commonplace on mountain bikes. Offering exceptional power during virtually any type of weather, hydraulic brakes are suitable for all forms of riding, from recreational single-track to precision-based riding such as the mountain bike trials. Though serious issues demand the attention of a professional bike shop, knowing how to fix minor issues can mean the difference between walking and riding home.

Things You'll Need

  • Clean rag
  • Needle-nose pliers
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Instructions

  1. Rotors

    • 1

      Clean the rotor of all debris to start, as this is enough to cause the brake to malfunction. Test the brake afterward to see if this corrects the problem.

    • 2

      Inspect the rotor for cracks, chips or any other damage. Spin the wheel and watch the rotor as it passes through the brake pads to determine whether it is warped and rubbing against the pads. Keep in mind that lateral movement of 1 millimeter is acceptable as long as the rotor is not rubbing the pads.

    • 3

      Replace the rotor if necessary and tote a spare rotor and tools on long trips to avoid having to walk home. Place a clean cloth over the rotor if a spare is not available and very gently bend the rotor as necessary.

    • 4

      Eliminate the source of squeaking by tightening the rotor bolts if necessary. Tighten the caliper bolts if necessary. Clean the pads, as dirt or other debris may be the source of noise.

    Levers

    • 5

      Adjust the brake levers so there is equal travel on both sides. Locate the reach adjustment screw near the meeting point of the lever and lever body and turn in or out until both brake levers travel the same distance toward the handlebars.

    • 6

      Bring your bike to a shop and have your mechanic bleed the brakes if the lever isn't firm when you pull it, as this may indicate air in the hydraulic system.

    • 7

      Check all the hoses and fittings on the brake lever body as well as on the brake itself where it meets the housing for leaks. Stop riding if leaks are spotted and bring your bike to the shop.

    Pads

    • 8

      Check the brake pads by first removing the wheels. Remove the pads by pulling on the pad removal tabs, using your hands and pliers.

    • 9

      Draw the pads straight out until unattached from the housing. Pull the pads toward the center of the caliper body. Remove any retaining hardware of the pads if necessary, depending on the model of brake.

    • 10

      Inspect the pads for uneven wear and general thickness. Replace the pad immediately if the thickness is less than 1/16 inch.

    Calipers

    • 11

      Check that the alignment of the calipers are correct to prevent drag. Visually inspect the angle of the caliper where the rotor runs through it; if the rotor is properly aligned, then the problem is caliper alignment.

    • 12

      Unscrew the centering bolt if using a two-part caliper brake bracket. Adjust the angle of the caliper.

    • 13

      Squeeze the brake lever while retightening the centering bolt. Grab the tire, spin the wheel and inspect the calipers and rotor once again to make sure alignment is correct.