When should you replace your bike chain?
The chain is the cheapest part of the drivetrain… and the most expensive one when you forget about it. Here is how to measure its wear in two minutes and know exactly when to replace it.
1. The principle: elongation
A chain does not really "stretch": the pins and bushings wear, which lengthens the chain pitch. This elongation is measured as a percentage.
- Under 0.5%: the chain is healthy, keep riding.
- 0.5%: replace the chain, the cassette can still be saved (0.75% for 8/9-speed drivetrains).
- Over 0.75%: chain + cassette, and often the chainring too.
2. Measuring with a simple ruler
- Shift onto the big chainring to put the chain under tension.
- Line the ruler up on a rivet pin and count 12 links (24 pins).
- On a new chain, this length is 304.8 mm (12 inches).
- 306.4 mm: 0.5% wear, replace the chain.
- 307.1 mm or more: 0.75% wear, plan for a new cassette as well.
A chain checker (a few euros) gives the same result faster: if the 0.75 side drops fully into the chain, it is already late.
3. Mileage guidelines by riding style
| Riding | Check | Typical replacement |
|---|---|---|
| Road / dry gravel | every 1,000 km | 2,500 – 4,000 km |
| MTB / mud | every 500 km | 1,000 – 2,000 km |
| E-bike | every 700 km | 1,500 – 2,500 km |
| City / short trips | every 1,000 km | 2,000 – 3,000 km |
These values are rough figures: lubricant, weather and cleaning can double or halve a chain's lifespan.
4. Making your chain last
- Clean and re-lube after every wet ride.
- Dry lube in summer, wet lube in winter.
- Wipe off excess lube: it attracts dust.
- Avoid cross-chaining (big chainring / biggest sprocket).
Track it automatically
MonSuiviVélo calculates your chain's wear percentage from your mileage (Strava import available) and warns you before the 0.5% threshold. The logbook also keeps a record of every replacement.