How to Reattach the Bicycle Rear Derailleur

How to Reattach the Bicycle Rear Derailleur
Without the rear derailleur in place on your bicycle, you'd be hard pressed, frankly, to shift gears any time soon. One of two derailleurs on a geared bicycle, the rear derailleur responds to a shift of the rear gear by moving the chain to the selected cog on the rear cassette. There are a couple of methods for reattaching a rear derailleur. The first involves separating the drive chain, while the second necessitates removing the lower pulley from the derailleur. The second method is often less messy and requires no special tools.


Difficulty: Moderately Easy


Things You’ll Need:
  • 5mm and 3mm Allen wrenches
  • Needle-nose pliers
  • Rag (as needed)
Step 1
Move the chain, by hand if necessary, to the largest front chain ring and outermost rear cog. If moving by hand, try using an old rag to reduce the potential for grime on your hand.
Step 2
Remove the 3mm Allen bolt at the center of the lower derailleur pulley, and remove the pulley from the pulley cage. Set the pulley and bolt aside for the moment.
Step 3
Use a 5mm Allen wrench to attach the rear derailleur pivot bolt, on the back of the derailleur, to the derailleur hanger. The derailleur hanger is located on the right, or drive-side of the bike frame just below the axle of the wheel.
Step 4
Spread the two plates of the pulley cage apart and pass the chain beneath the upper pulley (the remaining pulley) so that the chain is securely beneath it.
Step 5
Press the lower pulley (the one you removed) against the inside of the chain until the pulley is back in its former place inside the derailleur cage. The chain should pass behind the pulley. Continue to hold the pulley steady. Seen from the side, the chain will form a reverse "S" around the two pulleys.
Step 6
Thread the lower pulley bolt through the middle of the pulley, and tighten the bolt with your 3mm Allen wrench. Release the pulley.


Step 1
Release all slack from the rear shift cable, by shifting the rear gear all the way down. Giving the cable maximum slack will ensure accurate cable adjustment.
Step 2
Turn the barrel adjuster at the back end of the derailleur all the way in toward the derailleur. Once the adjuster is in, turn it counterclockwise two turns.
Step 3
Pass the rear shift cable through the cable opening at the back of the derailleur.
Step 4
Pull the end of the cable taut with a pair of needle-nose pliers and tighten the cable beneath the anchor bolt on the bottom of the derailleur. The bolt uses a 5mm Allen wrench.
Step 5
Shift the chain to the next cog over. If the chain refuses to shift, turn the adjuster barrel counterclockwise until the chain shifts to the cog.

Article Written By Matthew Ferguson

Matthew Ferguson is a writer living in Savannah, Ga. He has been writing for over 10 years and his work has appeared on various online publications. A collection of his short stories was published in spring 2010. He is a graduate of Appalachian State University.

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