How to Adjust Mechanical Bicycle Gears

For a mechanical derailleur drivetrain, first inspect the wheel, chain, cables, derailleur, and hanger. Then set the derailleur limits and cable indexing in the sequence required by the component maker. Do not use limit screws to compensate for a bent hanger or damaged drivetrain.

Do not ride if the derailleur or hanger is bent, the chain can shift past the largest cog toward the spokes, the wheel is loose, or drivetrain parts are cracked. A mechanic should inspect the bike before it is ridden.

Identify the shifting system

This procedure covers common cable-operated derailleur gears. Electronic shifting, internally geared hubs, continuously variable hubs, and vintage friction systems have different adjustment steps. Find the exact model number and use its service manual.

Clean the cassette and chain before diagnosing an adjustment problem. A dirty or worn drivetrain can shift poorly even when indexing is correct. Start with cassette cleaning and inspect chain wear using the chain maker’s limits.

Inspect before turning screws

Check that the wheel is fully seated and secure, the derailleur hanger looks straight, the cable housing is seated in every stop, and the chain has no stiff or damaged links. Look for frayed cable strands and crushed or contaminated housing.

If shifting became poor after a crash or wheel change, suspect alignment or installation before cable tension. Park Tool’s advanced derailleur troubleshooting identifies hanger alignment and cable friction as common causes that indexing alone will not fix.

Set rear-derailleur limits and indexing

Use the derailleur manufacturer’s instructions because screw labels, cable routing, pulley gap, and setup gauges vary.

1. Shift to the smallest rear sprocket and put the front derailleur in the position specified by the manual.
2. Release cable influence only if the procedure calls for it.
3. Set the high limit so the guide pulley aligns with the smallest sprocket without allowing the chain to fall outward.
4. Reconnect or tension the cable as directed.
5. Shift one click toward a larger sprocket while turning the cranks by hand.
6. If the chain hesitates to climb, add cable tension in small barrel-adjuster increments. If it hesitates to move outward, reduce tension.
7. Check every sprocket in both directions.
8. Set the low limit so the chain reaches the largest sprocket but cannot move into the spokes.
9. Set pulley-to-cassette clearance only to the exact model’s specification or gauge.

Park Tool’s rear derailleur adjustment guide explains why the high limit must be checked without the cable masking its position.

What about the front derailleur?

Front derailleurs require correct height, rotation, low and high limits, and cable tension. Compatibility depends on chainring count, tooth range, cable pull, frame geometry, and drivetrain family. Use the exact dealer manual. Our Shimano front-derailleur guide offers a more focused starting point, but the model manual remains controlling.

Test the result safely

Turn the cranks by hand through every allowed gear combination while the bike is secure. Check that the chain cannot leave the cassette or chainrings. Take a low-speed test ride away from traffic and avoid shifting under heavy pedal load.

If adjustment will not remain consistent, stop changing screws and diagnose the cause. A worn chain or cassette, bent hanger, poor cable routing, incompatible parts, or loose wheel needs repair. The bike tool-kit guide can help identify suitable hand tools, and the pedal guide covers a separate source of drivetrain-area noise.

This article is research-based and does not provide model-specific clearances or torque values.