How to Change a Freewheel Cog

Your bicycle contains a mechanism called a "freewheel." The freewheel threads onto the hub of your rear wheel. The freewheel is fitted with one or more cogs, which form an integral part of your bicycle's gearing. Generally, a cog is replaced either because it is worn, or a different sized cog is preferred in its place. In any instance, learning to replace freewheel cogs correctly saves time and potential damage to the freewheel itself.

Things You'll Need

  • Freewheel cog remover
  • Adjustable wrench
  • Waterproof bicycle grease
  • Chain whip
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Instructions

  1. Removal

    • 1

      Unbolt the quick release skewer from the axle of your rear wheel. Remove the skewer.

    • 2

      Select the proper freewheel cog remover. Different freewheel cog removers fit different freewheels. Each freewheel cog remover has a series of notches designed to fit the notches at the center of your freewheel. A proper freewheel cog remover will fit in the center of the freewheel similar to a key.

    • 3

      Insert the notch-end of the freewheel cog remover into the center of the freewheel.

    • 4

      Insert the quick release back through the axle of the wheel. Thread its bolt back onto its end so that the bolt is snug against the end of the freewheel cog remover.

    • 5

      Hold the wheel firmly while using an adjustable wrench to turn the freewheel cog remover counterclockwise. Turn the freewheel cog remover one revolution only.

    • 6

      Unbolt the quick release skewer, and once again remove it from the wheel.

    • 7

      Continue to rotate the wrench and freewheel cog remover to unthread the freewheel and its cog(s) from the side of the wheel. The part of the wheel to which the freewheel is attached is called the "hub."

    Installation

    • 8

      Rub waterproof bicycle grease along the internal threads at the center of the freewheel using your fingers. Cover the threads with grease liberally.

    • 9

      Place the wheel on the ground so that its hub is face-up.

    • 10

      Direct the replacement freewheel onto the hub so that its axle is centered in the hollow of the freewheel.

    • 11

      Turn the freewheel cog(s) clockwise to thread the freewheel onto the hub. Tighten the freewheel by hand to ensure that it is seated.

    • 12

      Set the wheel upright on its tire. Place the chain of a chain whip tool across one of the freewheel cogs.

    • 13

      Turn the chain whip tool handle clockwise to fully tighten the freewheel.