Why Your Bike Chain Skips Under Load—and How to Fix It, by DIY Mountain Bike on YouTube. 3 min 32 s.
- Video length
- 3 min 32 s
- Time to do it
- 45 minutes
- Difficulty
- Medium
- Steps
- 8
What you need
Steps
Ride or spin the bike and watch the chain. If it jumps between cogs, the problem is shifting. If it slips but stays on the same cog, the cassette is the suspect.
Narrow it down to two causes: derailleur or hanger misalignment for shifting, and worn cassette teeth for skipping in one gear.
Check the cassette even if the teeth look fine. Wear is often subtle, and a new chain will not mesh with deformed teeth.
Look closely at the tooth tips. Worn teeth show flattened, hooked or hammered shapes where the chain has beaten them down.
Compare the old chain with a new one. If the old chain is stretched, replace chain and cassette together so they wear in as a pair.
Remove the rear wheel and fit the cassette lockring tool. Hold the cassette with a chain whip and turn the lockring anticlockwise to loosen it.
Slide the old cassette off the freehub, fit the new one with the spacers in the right order, and tighten the lockring to the torque marked on it.
Refit the wheel, check the derailleur alignment and indexing, then test ride in a low gear under hard pedalling to confirm the skip is gone.
Tips and common mistakes
Count the teeth on your biggest and smallest cogs before buying a replacement so the new cassette matches your gearing.
A bent derailleur hanger can mimic cassette wear, so check it is straight before spending money on parts.
Clean and lubricate the chain after fitting the new cassette to help it seat properly.
Wear gloves when handling the cassette and chain, and keep fingers clear of the chainring teeth.
Questions
How do I know if my cassette is worn or my gears just need adjusting?
If the chain jumps between gears, adjust the derailleur and cable tension. If it slips while staying in one gear, the cassette teeth are likely worn.
Can I fit a new chain on an old cassette?
You can, but a stretched chain and worn cassette often skip together. Replacing both at once gives the best mesh and smooth power transfer.
Do I need special tools to change a cassette?
Yes, you need a cassette lockring tool and a chain whip. A large spanner or socket helps turn the lockring tool.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
