Why does the chain click against the next cassette sprocket?

A chain that sits on one cassette sprocket but repeatedly touches or climbs the neighbour is not always fixed by turning the barrel adjuster. If one adjustment makes another gear worse, check alignment, wheel seating, cassette security, cables, wear, and compatibility before continuing to tune tension.

The short answer: note which cog and which side makes contact, reseat and secure the rear wheel, inspect cassette play and chain condition, then test indexing in every gear. Uniform noise across the cassette often points to cable adjustment; one stubborn area can indicate hanger alignment, a damaged sprocket, cable friction, or a compatibility problem.

The current question behind this guide

A recent r/bikewrench post showed a chain seated on one sprocket but catching the next smaller sprocket and clicking back down. Barrel adjustment traded one problem for another.

That is a useful diagnostic signal: indexing is a system. A small cable turn cannot correct a bent mounting point, loose cassette, damaged cog, or wrong component combination.

Record the pattern before adjusting

With the bike secure and clear of fingers, turn the cranks forward by hand and shift one click at a time. Record:

• the selected sprocket;
• whether the chain touches the larger or smaller neighbour;
• whether it happens under light forward pedalling, load, or both;
• whether every shift in one direction is slow;
• whether the fault is limited to one or two sprockets; and
• whether it began after a wheel change, crash, cable replacement, chain replacement, or transport.

Do not diagnose from backpedalling alone. Many drivetrains behave differently in reverse because the derailleur no longer guides the chain into the cassette in the designed direction.

Check the wheel and cassette first

Make sure the rear wheel is fully seated and the quick release or thru-axle is installed to the bicycle manufacturer’s instructions. A wheel sitting differently in the dropouts changes cassette position relative to the derailleur.

Then check for cassette movement. The sprockets should not rock as a loose stack. Some freehub mechanisms have normal rotational movement; side-to-side sprocket looseness is different. If the cassette is loose, stop and identify the correct lockring, spacer arrangement, freehub, and specified torque before repair.

Spin the wheel and look for an obviously bent sprocket, damaged tooth, or foreign material between cogs. Remember that modern shift ramps and tooth profiles are intentionally uneven. Compare suspicious areas with the maker’s diagrams rather than filing a tooth that merely looks unusual.

Separate indexing from alignment

Indexing controls where the derailleur stops for each shifter click. On a compatible, straight, healthy system, small barrel-adjuster changes can centre the chain and make shifts clean.

Use the exact service manual because adjustment direction and reference gear differ. Make quarter-turn changes, shift through the full cassette, and write down the result. Return to the starting point if the change does not improve the whole range.

Suspect something beyond basic indexing when:

• one end of the cassette improves while the other gets worse;
• the chain is quiet on most cogs but catches in one local area;
• good adjustment cannot be repeated after shifting up and down;
• the cable feels sticky or fails to release consistently; or
• the derailleur cage does not appear parallel to the sprockets.

Shimano’s current derailleur guidance explicitly notes that shifting will not adjust correctly if the hanger is not straight and calls for an alignment tool.

Inspect the derailleur hanger

A hanger can bend from a small fall, transport pressure, or the bike resting on the derailleur. Looking from behind can reveal a severe bend, but visual inspection cannot verify small alignment errors across multiple planes.

Do not compensate for suspected hanger misalignment with limit screws. Limit screws set the derailleur’s travel boundaries; they are not indexing controls.

A mechanic or experienced home technician should measure the hanger with an alignment gauge, first confirming the wheel is true and correctly installed. Replace a cracked, twisted, or unsuitable hanger. Check the frame and derailleur too if there was an impact. Read the bent-hanger guide before deciding the repair scope.

Check cable movement and derailleur condition

For mechanical shifting, inspect exposed inner cable for fraying, corrosion, kinks, or a damaged ferrule. Confirm the housing is fully seated in every stop. Turn the bars through their range and check that cable routing does not pull the derailleur.

Contaminated or damaged housing can make the derailleur reach a different position depending on shift direction. Replacement means correct cable routing, end preparation, clamping, and adjustment—not adding lubricant to an unknown sealed system.

For electronic shifting, check battery state, connectors, crash-recovery procedure, firmware guidance, and micro-adjustment for the exact system. Do not apply a mechanical cable procedure to electronic components.

Inspect derailleur pulleys for damage, play, poor rotation, and correct installation. Confirm the derailleur mounting bolt is secure to specification and the B-gap is set by the maker’s method.

Check chain, cassette, and compatibility

Measure chain wear with a suitable tool and the chain maker’s threshold. Inspect for a stiff link and correct routing through both jockey wheels. If the noise began after a new chain, a worn cassette can skip or run poorly under load; see chain or cassette replacement.

Verify shifter speed count, derailleur, cassette, chain model, freehub spacing, and any required spacers. “Ten speed” or “Shimano compatible” alone may not prove that every part belongs to the same indexing system.

Complete a controlled test

After correction:

1. shift one gear at a time through the full cassette in both directions;
2. confirm the chain does not approach the spokes or dropout;
3. test with the front chainring positions normally used;
4. listen for repeated contact in every rear gear;
5. make a low-load ride in a traffic-free area; and
6. stop if the chain jumps, overshifts, or the fault returns under load.

Do not place the bike straight into traffic or a hard climb after a stand-only adjustment.

Your next step

Record the exact noisy sprocket and contact direction, reseat the wheel, check cassette security, and follow the model-specific indexing manual once. If improvement cannot be achieved across the whole cassette, stop turning adjusters and have hanger alignment, cables, wear, and compatibility measured.

Sources and further reading

• Shimano rear-derailleur service guidance and adjustment references
• Shimano derailleur guidance noting hanger alignment is required for correct shifting
• r/bikewrench reader context: chain catching the adjacent cassette sprocket