Troubleshooting › Shifting & chain

Shifts by itself: causes and fixes

Gears that change on their own usually mean the cable tension is between two gears.

Check it on your own bike

1. Cable tension between two gears · Most likely

   Fine-tune the barrel adjuster until the chain sits quietly in each gear.

   Fix: Adjust rear derailleur (limits + indexing)

2. Housing compressed or kinked · Sometimes

   Turn the bar fully both ways while pedaling. If it shifts, a housing is too short or kinked.

   Fix: Replace shift cable and housing

3. Bent hanger · Sometimes

   A bent hanger makes tension correct in some gears and wrong in others.

   Fix: Check and straighten derailleur hanger

4. Rear wheel slipping in the dropouts · Sometimes

   Make sure the rear quick release or axle nuts are tight.

   Fix: Use a quick release properly · Install a thru-axle wheel · Remove and refit a bolt-on wheel