Chain Length for Bike

I don’t treat chain length as an exact science. The simplest way to find best chain length is to use the largest sprocket technique.

• Simply take a new chain and put it in the largest front chainring (e.g the 50 or 52 tooth outer chain ring.
• Then put it on the largest cassette sprocket at the back, nearest wheel. This will be a 25 or 27 tooth sprocket.
• Don’t put chain through rear derailleur at this point.
• Pull the chain tight and see where it meets; to this then add an extra two links. This chain length including the two links is the ideal size of a chain.

(Note when riding, you wouldn’t use this combination of biggest chain ring and lowest cassette sprocket (highest number of teeth). This is because such a combination gives a bad angle for the chain. It is more likely to grate against derailleur’s e.t.c. You should be going down into the lower chainring.)

When threaded through the rear derailleur, the chain should be workable in all the gear combinations that you are likely to use.
The chain should be tight, without putting too much pressure on the rear derailleur. If the rear derailleur is pulled so it is almost vertical pointing down, this is a sign the chain is too short.

With this chain length, if you had to shorten chain on a ride (because it snapped) you could ride on it. But, you would have to be more careful when using big chain ring and make sure you didn’t use combination of big chainring and low cassette.Once you have the correct chain length, you can just use that chain length to copy any new chain you put on.

How Often to Change Chain?

I try to change a chain every 1,000 miles. Unless it is a commuting bike / touring bike, in which case I may keep it on for 3,000 – 4,000 miles. More details – how often to change a chain?

Rear Cassette replacement

Chain length at Park Tools

Chains at Wiggle Cycles