Symptoms
- Chain skips or jumps between gears under load
- Pedaling feels like it suddenly loses resistance
- Noise or clicking when pedaling hard
- Chain occasionally comes off the chainring
Likely causes
- CommonWorn or stretched chainChains stretch with use and no longer mesh properly with the gears.
- CommonRear derailleur out of adjustmentCable tension changes over time and can cause imprecise shifting and slipping.
- PossibleWorn cassette or chainring teethWorn 'shark fin' shaped teeth can't hold the chain properly under load.
- PossibleDirty or dry chainLack of lubrication increases friction and can cause skipping.
What to do
- Check the chain for obvious wear using a chain wear indicator tool, since a stretched chain is the most common cause.
- Clean and lubricate the chain if it looks dirty or dry.
- Check rear derailleur cable tension; a barrel adjuster on the derailleur or shifter can fine-tune this.
- Shift through all gears and watch for the chain hesitating or skipping in specific gears, which points to that particular cog being worn.
- Inspect the cassette and chainring teeth for hook-shaped wear.
- Replace a stretched chain, and the cassette too if it shows matching wear, since a new chain on a worn cassette can skip.
- If adjustment and chain replacement don't resolve it, a bike shop can check derailleur hanger alignment.
Tools and parts
- Chain wear indicator
- Chain lubricant
- Screwdriver for barrel adjuster
Bike chainSearch: “bicycle chain replacement correct speed”
Bike cassetteSearch: “bicycle cassette replacement”
When to call a pro
A bike shop can measure chain and cassette wear precisely and replace both together if needed, and check for a bent derailleur hanger.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.