Garage tool 06

Chain length

The question after the gearing change: will my chain still fit?

Start from a bike's stock gearing

Pick a bike to fill in its stock sprockets and chain pitch.

Chain pitch

Links now (count them)

Now

Front teeth

Rear teeth

After the change

Front teeth

Rear teeth

Chain you need

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Worked from the standard chain-length formula. Real axle positions vary with adjuster setting; if the result sits at the end of the adjusters, go up or down two links. Replace chain and sprockets together.

Rule of thumb

Two teeth on the rear, or about one on the front, is roughly one link of chain. The calculator does it exactly: it works out your axle-to-countershaft distance from the chain you have, then the length the new sprockets need, rounded up to an even number of links. Pick the gearing first in the gearing calculator.