Chain length

Sizes a chain from frame geometry rather than by wrapping it round the bike. Measure the chainstay once and the answer holds for any chain you fit.

How to measure this

3 steps

Bottom bracket centre to rear axle centre, on the bike. If the wheel slides in the dropouts, measure it where you actually ride it.

Chainstay length

Bottom bracket centre to rear axle centre. Measure it on the bike, in the gear you will ride.

Largest chainring

Largest cog

Suspension chainstay growth

Full suspension frames lengthen through their travel. If you know how much, add it — otherwise leave at zero.

Measure across 24 links with a ruler, pin centre to pin centre. A new chain measures exactly 12 inches.

Measured over 24 links

Speeds