Why chains wear
Chains don't really stretch. The pins and rollers wear, so each link gets a fraction of a millimetre longer. A longer chain no longer sits properly on the teeth, so it starts wearing your cassette and chainrings into its own shape.
Change the chain early and the cassette keeps going. Leave it too long and a new chain will skip on the worn cassette, so you end up replacing both.
How to check
- Shift onto the big chainring so the top run of chain is under tension.
- Hook one end of the wear checker into a link and let the other end drop in. Don't force it.
- If the 0.5 side drops fully in on 11 or 12-speed, or the 0.75 side on any chain, it's time.
- Move the chain round and check in three places. Go by the worst reading.
When to replace
| Your gears | Replace at | Roughly every |
|---|---|---|
| 12-speed | 0.5% | 1,500–3,000 miles |
| 11-speed | 0.5% | 1,500–3,000 miles |
| 9 and 10-speed | 0.75% | 2,000–3,500 miles |
| 8-speed and below | 0.75% | 2,500–4,000 miles |
Mileages are only a guide. Wet, gritty winter roads and muddy trails can halve them.
Rule of thumb: most riders get through two or three chains for every cassette, as long as each chain is swapped when the checker says so.
What waiting costs
A new chain costs around £20. A worn-out drivetrain means a new chain, cassette and often chainrings, which can easily cost £100 or more.
Choosing a new chain
- Match the speed. Buy a chain for the number of sprockets on your cassette.
- Match the length. If your old chain shifted well, make the new one the same number of links.
- Use a new quick link. Most quick links are designed to be used once.
Our guide Which chain fits my bike? goes into more detail.
FAQs
Can I mix Shimano and SRAM chains and cassettes?
On 11-speed, usually yes. On 12-speed, use the chain made for your groupset. SRAM Flattop chains only work with Flattop chainrings and cassettes.
Do I need a new cassette at the same time?
Not if you replace the chain on time. If the new chain skips under load, the cassette is worn too.
How often should I clean and lube my chain?
Wipe and lube every week or so in winter, and every 100–200 miles in the dry. Lube the rollers, then wipe the outside clean.
What tools do I need to fit a chain?
A chain tool to shorten it, and quick link pliers make fitting and removing the link much easier.