How to Adjust a Bicycle Rear Derailleur

How to Adjust a Bicycle Rear Derailleur
A rear derailleur is a mechanism located just above the rear hub of a road or mountain bike and is part of the gear shifting system of the bike. The derailleur essentially moves the chain from one sprocket of the bike to another as determined by the rider. By moving the chain to larger or smaller sprockets the gear ratio is affected, which helps the rider maneuver hills and flat. The derailleur is controlled by a cable attached to a gear shift lever near or on the handle bars.


Difficulty: Moderate

Things You’ll Need:
  • Bike with gears
  • Screw driver
  • Bike lubricant
Step 1
Select the lowest gear on the gear shifter. Rotate the rear wheel and allow the derailleur to move the chain to the largest sprocket on the cassette.
Step 2
Examine the sprockets to see if the derailleur or any part of the shifting assembly is making contact, especially with the largest sprocket. Adjust the alignment screw located near the top rear of the assembly. Use a screw driver to make 1/4-inch adjustments at a time. Turn to the right to increase distance between the sprockets and derailleur.
Step 3
Adjust the tension in the shifting cable if necessary. There should not be any tension at this point in the lower cable. Turn the cable adjusting nut, located at the point where the cable connects to the derailleur, to the right.
Step 4
Position the shift lever to the highest gear setting. Rotate the back wheel to allow the chain to move from the largest sprocket to the smallest and determine if the chain rides securely on the small sprocket or attempts to travel toward the axle. Locate the two small screws located on the side of the derailleur, one above the other. Adjust the upper, or H, screw until the side motion of the chain stops.
Step 5
Tighten the cable using the barrel nut to increase the tension and shift the gears back to the lowest setting. Turn the wheel and watch the chain move to the largest sprocket to see if it is centered or continues to move. Adjust the bottom or L screw until the chain rides center on the sprocket.
Step 6
Spin the rear wheel and shift through the gears. Adjust the cable tension by turning the barrel adjustment nut until the chain travels smoothly through the range of gears. Attempt to shift through all of the gears in both directions so you can diagnose whether it is shifting properly. Lubricate the derailleur mechanism, sprockets and chain with bike oil.

Tips & Warnings

Turn the barrel adjustment nut clockwise, or to the right, if the chain is having difficulty moving to smaller rings or shifting up. Turn the barrel the opposite direction for difficulties shifting down.
Watch possible pinch points when working on derailleurs.

Article Written By Keith Dooley

Keith Dooley has a degree in outdoor education and sports management. He has worked as an assistant athletic director, head coach and assistant coach in various sports including football, softball and golf. Dooley has worked for various websites in the past, contributing instructional articles on a wide variety of topics.

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