The rear derailleur takes more punishment than almost any other part of your bike. It hangs exposed at the back, takes impacts from rocks and curbs, and gets caked in mud and chain grease. Regular servicing keeps shifting crisp and extends the life of your drivetrain significantly.
What You Need
- Degreaser and a cleaning brush
- Chain lubricant
- 3mm and 5mm hex keys
- A barrel adjuster tool or small screwdriver
- A bike stand or way to hold the bike off the ground
Step 1: Clean Everything First
Apply degreaser to the derailleur body, jockey wheels, and the cage. Use a brush to work it into the jockey wheel teeth and the parallelogram pivots. Wipe clean with a rag and allow to dry before proceeding. A dirty derailleur cannot be adjusted accurately — grit in the pivots affects movement.
Step 2: Check the Limit Screws
The H (high) and L (low) limit screws control how far the derailleur moves toward and away from the wheel. Shift to the smallest rear sprocket and check that the jockey wheel is directly below it — adjust the H screw if not. Then shift to the largest sprocket and verify the jockey wheel lines up there too, with no rubbing on the spokes. The L screw controls this end.
Step 3: Set the B-Tension Screw
The B-tension screw sets the gap between the upper jockey wheel and the cassette sprockets. Shift to the largest sprocket and check the gap — it should be 5–7mm on most derailleurs. Too close and the jockey wheel will skip; too far and shifting becomes sluggish. Adjust the screw until the gap is correct.
Step 4: Cable Tension Adjustment
Most poor shifting comes from incorrect cable tension. Shift to the smallest sprocket, then shift one click toward the largest sprocket. The chain should move smoothly one sprocket. If it hesitates, increase cable tension by turning the barrel adjuster counterclockwise by a half turn at a time until shifting is crisp across the whole cassette.
Step 5: Lube the Jockey Wheels
The jockey wheel bushings dry out over time and cause noise and wear. Apply a small drop of light oil to the center of each wheel. Spin them by hand to distribute the lubricant and wipe off any excess from the outer surfaces.
Serviced every few months, a rear derailleur will give years of reliable use. Neglected, it will cause frustrating shifting problems that are almost always avoidable.