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How to Size a Bicycle Chain

Learn how to size a bike chain from Silk Road Cycles' Brendon Nicholas in this Howcast bicycle repair and maintenance video, part two of three.


To install a new chain, you want to make sure that you're using the correct size. So to find out the size of your chain, basically it's the speeds of your bicycle.

So in the rear here, you'll see, if you count each cog, there's one, two, three, four five, there's nine cogs here. There'll be anywhere usually from five cogs to now there's 11 cogs and you need a special chain for each size. Basically a chain width is different for each size. So you find your box that says a nine speed chain and you take out the chain. We'll just use the old chain just as an example here and you're going to shift your gears all the way up to the largest or lowest gear in the back and all the way up to your highest and largest gear in the front. So this is how you're going to size your chain to make sure that it's the proper length and that you're not going to have too much slack or not enough. So you want to make sure that you're weaving the chain through just the way that it came out. Make sure it's going along these rollers and through the proper way.

So now that you're on the two largest cogs, so the largest in the back and the largest in the front, you're going to stretch your chain all the way so the derailer can't stretch anymore. So that's where you're going to break your chain. You're going to add one link. So one full link is right here. That size right there. You add that and cut off the rest and that's the length of your chain so it would look like this when it's put together.

So the way to put together this chain is they use a pin. So it comes in these little packets here. Different chains require different installation. This chain requires a pin which you'd have to get at a bike shop according to whichever size chain you have and this is a Shimano specific pin. They also have quick links which I demonstrated before so these are the quick links. Or the chain may all ready have the pin installed on one side and it's just coming out of one side of the chain and then you can just push it through to connect properly.

So now that you have the sizing correct and you have your pin, make sure that you're shifting down to whatever is the smallest cog in the front and whatever the smallest cog in that back so you have a lot of slack and you can actually even take it off your chain ring in the front so it's nice and loose. And then you're going to take the basically the male and female side, put them together and then put the pin through and that holds them together.

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