How To Repair a Bent Derailleur Hanger

A derailleur hanger is the piece of metal that hangs on a bicycle beneath the right dropout that attaches the rear derailleur. The derailleur easily can get bent in a bicycle wreck. On most bikes nowadays, the derailleur hanger is a separate piece that can be taken off the bicycle to be repaired. A bent derailleur hanger can cause the bike chain to skip cogs or can make the chain jump off the chain rings during back pedaling.

Things You'll Need

  • Hex wrench
  • 10 mm fine-pitch bolt
  • Wrench or socket set
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Instructions

    • 1

      Remove the derailleur hanger by removing the derailleur mounting bolt with the hex wrench.

    • 2

      Turn the 10 mm fine-pitch bolt into the derailleur hanger with the wrench or socket. Leverage the end of the bolt to straighten the metal of the derailleur hanger.

    • 3

      Examine the straightness of the derailleur hanger with a carpenter's square.

    • 4

      Remove the 10 mm fine-pitch bolt from the derailleur, and then set the derailleur back on the frame near the right dropout. Replace the derailleur by slipping the mounting bolt back through and tightening it down with the hex wrench.