How to Replace Freewheel Sprockets

A freewheel is the element of a hub on a rear bicycle wheel that engages to let the chain drive the wheel, then releases to allow the wheel to spin freely when the chain is not moving. Sprockets attached to the freewheel determine the force applied to the wheel. Sprockets must be changed sometimes because a rider wants a different gear ratio or because they are worn or damaged. An owner can do this himself with the right tools and basic mechanical knowledge.

Things You'll Need

  • Freewheel puller or cassette tool
  • Wrench set
  • Chain whip
  • Vise (optional)
  • Channel lock pliers
  • Sprocket or cassette sprocket set
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Instructions

    • 1

      Determine what type of hub system your bicycle has. For many years, bicycles had traditional freewheels that were attached to the hub with threads. Sprockets then were fastened to the freewheel with threads. Since the 1980s, most manufacturers have switched to a "freehub" design developed by Shimano, which uses a cluster or cassette of sprockets rather than individually attached sprockets. The freehub also is held in place with splines rather than threads. Removal of freewheels and sprockets is similar with both styles.

    • 2

      Remove the rear wheel from the bicycle. Then you will need to get a freewheel puller that fits your specific hub; there are different tools for different makes of freewheel --- a bicycle shop can get you the proper one. For threaded freewheels, the usual technique is to clamp the freewheel puller in a vise, then put the wheel on it and turn the wheel to release the freewheel. For freehub styles, use a cassette tool, which fits into the cassette lock ring. Secure the cassette with a chain whip locking device, then turn the tool to the left until the lock ring releases.

    • 3

      Replace worn or damaged sprockets. With freehub cassettes, this involves installing an entire new cassette of sprockets; you will have to buy a set with whatever gearing you want. Just fit the new cassette into the spline grooves --- it may take some tinkering to get it on --- then reinstall the lock ring. With older bicycles, you use a chain whip and a vise (or two chain whips) to hold the freewheel securely while you unscrew the sprocket (or sprockets --- if you're changing just the middle sprocket in a set, you'll have to remove all those above it). Screw on the new socket, then reinstall the freewheel.