How to Repair a Bike Gear

Modern bicycles have many gears, so it's only natural they go bad from time to time. Gears can get hit by road debris, damaged by too much chain torque, or suffer from a bad shift at the wrong time. Individual gears are usually not repaired but instead replaced as a complete set. You can fix minor problems, however, such as a bent tooth on an individual gear that causes poor shifting or prevents the chain from running smoothly. First you must remove the gear cluster. There are two types of gear clusters: freewheel, and cassette. Both are easy to remove.

Things You'll Need

  • Freewheel socket
  • Large adjustable wrench
  • Channel-lock pliers
  • Chain whip
  • Cassette socket
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Instructions

  1. Freewheel

    • 1

      Take the wheel off the bike. Take the tire off the wheel. Remove the skewer lever and knob from the wheel axle and pull out the skewer. Set it aside.

    • 2

      Stand the wheel up on the floor with the gear cluster facing away from you. Hold the wheel between your feet with the back of the wheel resting against your legs. Bend forward and place the freewheel socket on the wheel, over the axle.

    • 3

      Place the adjustable wrench on the freewheel socket and push down, turning the socket counterclockwise. This will unlock the freewheel. When it comes loose, put down the wrench and finish unscrewing the freewheel cluster with your fingers. When it comes loose, pull it free of the axle.

    • 4

      Pry the bent tooth back up to vertical with the channel-lock pliers. Check the remaining teeth by spinning the gear cluster at eye level. If all teeth look straight, screw the freewheel back on the axle. Put the freewheel socket back on the end of the freewheel. Put the adjustable wrench back on the socket and turn clockwise to tighten and lock it back on the wheel.

    • 5

      Put the skewer back in. Screw on the skewer knobs and put the tire back on the wheel. Put the wheel back on the bike.

    Cassette

    • 6

      Take the wheel off the bike. Take the tire off the wheel. Remove the skewer lever and knob from the wheel axle and pull the skewer out. Set it aside.

    • 7

      Place the wheel on the floor and brace it against your legs. Place the chain-whip over the gears. The chain-whip fits on the gears just like the bike's chain, except it has a handle. Place the cassette socket on the axle. Place the adjustable wrench on the socket. Using the chain whip handle for leverage, push down counterclockwise on the wrench, unlocking the cassette.

    • 8

      Remove the chain-whip and the cassette tool. Finish unscrewing the cassette with your fingers and pull if free from the axle.

    • 9

      Pry the bent tooth back to normal with the channel lock pliers. Slide the cassette back on, put the chain-whip and cassette socket back on, and tighten them both back on just like they came off.

    • 10

      Remove the chain-whip and cassette socket. Put the skewer and skewer knobs back on. Put the tire on the wheel and put the wheel back on the bike.