Why is my bike chain skipping? (causes and fixes)
A chain that skips, slips, or jumps under power is one of the most common — and most annoying — drivetrain problems. The good news: it's almost always one of a handful of causes. Here's how to track it down, roughly in order of likelihood.
1. A worn-out cassette (especially with a new chain)
This is the classic. If you just fitted a new chain and now it skips under hard pedaling, the cassette is worn out. The old, stretched chain reshaped the cassette teeth, and the new chain no longer meshes. The fix is a new cassette — see when to replace your cassette.
2. A worn, stretched chain
A chain past its wear limit rides up on the teeth instead of seating, and skips under load. Check the chain first — it's the quickest thing to rule out, and replacing it on time prevents most of the other problems here.
3. A stiff or damaged link
One tight link will cause a regular skip or "tick" that you can often feel. Backpedal slowly and watch the chain pass through the rear derailleur — a stiff link jumps as it tries to bend around the pulley. Flex it side to side to free it, or replace the link.
4. Cable tension / indexing out of adjustment
If the skipping is really the chain hopping between two gears or hesitating to shift, it's usually indexing, not wear. A slightly stretched shift cable throws the alignment off. A few clicks of the barrel adjuster usually sorts it.
5. A bent derailleur hanger
If shifting is vague across the whole cassette and won't index no matter what, the hanger (the small bracket the rear derailleur bolts to) may be bent — common after the bike tips over. It's a cheap part but usually needs a shop tool to realign or replace.
6. Worn chainrings or jockey wheels
Less common, but hooked chainring teeth or worn derailleur pulley wheels can cause skipping that a new chain and cassette didn't fix. See chainring wear.
How to diagnose it quickly
- Did it start right after a new chain? → cassette is worn. (#1)
- Old chain, lots of miles? → check chain wear. (#2)
- A rhythmic single skip? → look for a stiff link. (#3)
- Hopping or hesitating between gears? → indexing/cable. (#4)
- Vague shifting everywhere? → suspect the hanger. (#5)
Most skipping traces back to letting a chain wear too long — which quietly takes the cassette with it. Catching chain wear early is the cheapest way to never see this problem in the first place.