Repair guides › Drivetrain
Measure chain wear
Transfers your pedaling to the rear wheel. It wears out first and takes the cassette and chainring with it if you wait too long. Pins and rollers wear, so the chain gets longer ("stretch"). A worn chain skips and grinds the cog teeth into hooks. Width depends on speed count: buy the one that matches your cassette. Replace at 0.75% wear for 8/9/10-speed, 0.5% for 11-speed and up.
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Tools
- Tape measure + 6" steel ruler: Stanley 16 ft tape measure ($)
- Chain wear checker: Park Tool CC-3.2 Chain Wear Indicator ($)
Compare Good, Better and Best for each tool
Steps
- Drop the checker into the chain on the top run with tension on the chain.
- If the 0.75 side drops fully in (8/9/10-speed), the chain is done. Use the 0.5 side for 11+ speed.
- Ruler method: line up the 0 on a pin center. 12 full links should end exactly on 12". At 12-1/16" (≈0.5%) replace an 11/12-speed chain; at about 12-3/32" (≈0.75%) replace an 8/9/10-speed chain. At 12-1/8" plan on a new cassette too.
- Log the reading. Catching wear early saves the cassette and chainring.
Diagram
Close-up of the partsChain
Signs it needs doing
- Chain skips under hard pedaling
- Noisy, gritty drivetrain
- Stiff link that clicks once per crank turn
- Rust