All Maintenance Tasks · Seasonal
Derailleur Indexing Tune
Indexed shifting works because a fixed amount of cable pull moves the derailleur exactly one sprocket. Cables stretch slightly, housing compresses, and dirt adds friction, so over a season that fixed amount stops matching. The result is a drivetrain that hesitates, rattles in some gears, and eventually drops a chain at the least convenient moment.
Interval
Seasonal
Four times a year, at the change of weather
Time on the job
25 minutes
Once you have done it a few times.
You or a shop
Some practice
The stop signs further down are the real answer.
Applies toRoadMTBHybridE-bikeKids
How often, really
Quarterly for a bike in regular use, and immediately after any new cable, since new cables settle noticeably in their first few rides. If you ride in the wet, dirt in the housing pushes this in closer. If shifting is crisp in every gear and quiet under load, leave it alone; a tune is a response to a symptom, not a ritual.
The interval on this page is Seasonal. Four times a year, at the change of weather.
What you need
- A stand, or a way to turn the pedals with the rear wheel off the ground
- A small screwdriver for the limit screws
- Hex keys for the cable anchor bolt
- The dealer manual for your shifting system
Doing the job
Rule out the things that look like indexing
Before touching an adjuster, check the chain is clean and lubricated, the cassette is not worn into hooks, the jockey wheels turn freely, and the cable is not frayed at the shifter or gritty in the housing. A worn chain skipping under load and a mis-indexed derailleur feel similar and have nothing in common.
Check the hanger is straight
Look at the rear derailleur from directly behind the bike. The two jockey wheels and the sprockets should all sit in the same plane. If the derailleur leans in toward the wheel, the hanger is bent, which is extremely common after the bike has fallen over on its right side. A bent hanger cannot be fixed with cable tension, and straightening one properly needs an alignment gauge.
Set the cable tension from the smallest sprocket
Shift to the smallest rear sprocket, where the cable is at its slackest. The chain should sit there without noise. This is the reference position: every adjustment that follows is measured from a drivetrain that starts here quietly.
Work the barrel adjuster in small turns
With the rear wheel off the ground and the pedals turning, shift up one sprocket. If the chain hesitates or will not climb, turn the barrel adjuster counterclockwise a quarter turn at a time to add tension. If it overshoots or rattles as if it wants the next sprocket up, turn it clockwise instead. Change one quarter turn, then test, then change again.
Check the whole cassette in both directions
Once the middle of the cassette shifts cleanly, run all the way up and all the way down, and pay attention to the extremes. Shifting that is perfect in the middle and poor at both ends usually means the limit screws rather than the cable. Those set how far the derailleur can travel, and they are adjusted with the derailleur at that end of its range.
Test it under load, on the road
A drivetrain that shifts beautifully in a stand can still hesitate under pedaling pressure. Ride it, shift under moderate load, and listen for a gear that rattles at the back. Bring it back and give the adjuster another quarter turn if it does.
Stop and take it to a shop
If any of this shows up while you work on derailleur indexing tune, put the bike down and let a mechanic look at it. None of these are things to ride out and see how it goes.
- The derailleur can reach the spokes, or the chain has come off past the largest sprocket even once. The limit screws are wrong and the next occurrence takes the derailleur into the wheel at speed. Stop and set the limits, or have it done.
- A visibly bent derailleur hanger or a derailleur cage that is no longer straight. Bending it back by hand cracks hangers and derailleurs, and both are best handled with the right gauge.
- A frayed shift cable at the shifter, or a cable that has broken strands inside the housing. Replace it rather than tuning around it.
- Shifting that will not come right after the cable, the hanger and the limits have all been checked. Something is worn or bent that is not obvious, and an hour of a mechanic time is cheaper than a rear derailleur.
Where this usually goes wrong
- Turning the barrel adjuster a full turn at a time, which overshoots the correct point and makes it impossible to tell which way you were going.
- Adjusting limit screws to fix an indexing problem. Limits define the ends of the travel and have nothing to do with the steps in between.
- Tuning a drivetrain with a worn chain, which produces a bike that shifts well for a week and then goes back to skipping.