How to Change a Derailer

You may have to change a rear derailleur after a crash, or if it is has experienced enough wear so it does not shift well between gears. If the chain slips when changing between gears, or if you suddenly cannot shift into the lowest and highest gears, it is probably a sign that the bike needs to have its rear derailleur changed. Fortunately, changing a derailleur is a simple process.

Things You'll Need

  • Bike stand (optional)
  • Hex wrenches
  • Phillips screwdriver
  • Grease
  • Needle-nose pliers
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Instructions

    • 1

      Place your bicycle on a bike stand or turn it upside down. This will allow you to work on it more easily.

    • 2

      Shift the bicycle to its lowest cog. This will produce the most slack on the chain.

    • 3

      Remove the idler pulley by unscrewing the bolt that holds it to the derailleur. It usually takes a hex wrench. This will allow the derailleur to separate from the chain.

    • 4

      Remove the old derailleur from the derailleur hanger by unscrewing the bolt that holds them together. This will require a hex wrench.

    • 5

      Loosen the hex bolt that secures the cable-retaining clamp. Pull the cable out of the derailleur, using needle-nose pliers, if necessary. Remove the end cap off the cable, if it has one. The derailleur should be free now.

    • 6

      Hold the new derailleur into position, making sure it is at the right angle. The tension screw must be above the notch of the hanger. Grease the mounting bolt and thread it into the hanger. Tighten it with the hex wrench.

    • 7

      Loop the chain through the sprockets. Look at another bicycle, if necessary, to make sure the chain is properly routed through the derailleur. Screw the idler pulley back into the derailleur.

    • 8

      Thread the cable through the receptacle on the back of the derailleur. Tug on it to remove any kinks, but keep it slack after it is fed through the cable clamp. Grab the end of the cable and pull it through the clamp with the needle-nose pliers.

    • 9

      Begin shifting the gears. Adjust the cable's tightness by pulling it farther through the clamp, or giving it more slack. If the bicycle has trouble moving between gears, adjust the position of the derailleur by screwing or unscrewing the limiting screws on it with a Phillips screwdriver.