How To Replace A Bicycle Chain

The chain on your bike wears out over time and eventually you’ll have to replace it. Fortunately, the process is pretty simple – Simon shows you how.
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First thing to do is find out whether your chain is joined together with a pin or with a quick link. If you have a quick link then technically you can remove the chain with your bare hands. Bear in mind though that when it comes to re-sizing your chain, you can only cut it down to the right size with the use of a chain tool.

If you don’t have your old chain to hand, or if you’ve changed your gear ratios and need a new size of chain, we’ve also got a failsafe way of finding the correct chain length for your bike!

It’s best to check for chain wear on a regular basis – leave it to long and it will damage your whole drivetrain.

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IO – Chocolate

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– [Simon] You periodically need to
replace the chain on your bike, either because the old one is worn out,
or perhaps because it’s been damaged, maybe even snapped. – [Matt] Are you [beep] kidding me? – Fortunately, it’s a simple process. All
you need is a new chain and then a chain tool. To remove the old chain, firstly
start by putting the gears in the smallest cog at the back and also the
smallest chainring in the front. This gives you the most possible amount of
slack in the chain to make removing the old one easier. To create even more slack
in the chain, I actually always unshift the chain from the chainrings altogether.
But if you’ve got a bike, and it works unlike that, you can just pop
the back wheel out as well. There are actually potentially two ways to
remove the chain from your bike, and you need to inspect carefully what you
currently have on there in order to find out which one you can do. Now, what you’re
looking for is a link a little bit like this one. Now, this is called a quick
link, and technically you can remove the chain without using any tools
altogether. You just push the two plates together slightly and then slide
them apart. In reality, they’re normally quite stiff, and so you at least need a
pair of pliers, but technically you can do it. If there is no quick link then you’re
going to have to use your chain tool to split the chain, but it’s a really simple
process. So simply put a link of the chain into the chain tool and then wind the
handle of the tool in towards the chain which drives the chain tool into it and
then pushes the pin of the chain out. Now carefully pull the chain off the
bike. Now, this isn’t destined for the bin quite yet. We need it for one last job,
and that is to check the length of the new chain and match it up with this
one. Now over to the work bench. Chain link varies from bike to bike
because of a lot of different factors but mainly because of the size of the gears.
So you always need to reduce the length of a new chain so that it fits your bike
correctly. So take your old one, stretch it out and then lay the new one
out next to it. Now, I need to mark the length of the new chain next to the old
one and then break it using a chain tool. But before you push the pin through, you
need to make doubly sure that the two ends of your chain are different. So by that I
mean one end is a narrow end like that then the other end is a wider end like
that so they actually fit together. Unless, of course, you are going to
rejoin your chain using a quick link, in which case both ends of the chain
here need to be narrow. So, it sounds complicated but it’s not. Both ends
need to be different unless you’re using a quick link in which
case they need to be the same. If for whatever reason you don’t have your
old chain to measure the new one against, or you’re changing the size of either
your cassette at the back here or your chainrings here. And so you need to adjust
the length of the chain anyway to account for a different of teeth, then you will
find the optimum length with this method. So you take your new chain, wrap the chain
around the biggest sprocket at the back and then the big ring at the front
but bypassing both derailleurs. Pull it tight and then add two links,
and that is your optimum chain length. See that? I’m pulling it tight, and
then I’ve got to add two links, so that’s one link, and that’s two links.
So, that link there is my optimum chain length. So now onto joining your
chain. If you haven’t already, make sure that you shift your gears into
the smallest ring, so down here at the back and then down here at the front.
And then thread your chain onto the bike. Pay particular attention when it gets to
the rear derailleur, so the chain goes around the cassette like that and then
loops back underneath, then over the top of the first jockey wheel. And then
pay particular attention to that pin. So the chain has to go above that and then
around the button jockey wheel, like so. Onto rejoining the chain now. Shimano
chains require a special joining pin like this one. So, it’s got a guide and
then the actual chain link there. So you start by simply pushing the thin
end into the closed chain, and then take your chain tool and push the actual link
into the chain, exposing the guide pin out the other side. And this can be
quite stiff, but that is a good thing. ♪ [music] ♪ There we go. Drive it untill it’s
flushed, and then we leave it like that. It’s important to note that once
you’ve used a Shimano joining pin, you should never break the chain on that
link there. Find one in many other hundred or so links to choose from but
don’t break it there again. And then, you then snap that off by using
a chain tool or a pair of pliers. ♪ [music] ♪ If you’re using a quick link, then you
simply slide the two place together and then lock them tight by applying pressure
to the chain. It really is that simple. And then the final point to mention is
that you buy the correct width chain for the number of gears you got. So chains are
sold according to the amount of sprockets that you’ve got on your cassette. The
greater the number of gears you have, the narrower your chain is going to be, so
this is a really narrow 11-speed chain for an 11-speed cassette. The other things,
well, Shimano, SRAM and Campagnolo will all tell you to only use
their chains on their gears, the idea being that they’re not compatible.
But third party chain manufacturers will tend to make chains that are compatible
with all three of them. So, go figure. So all in all then, a pretty simple
process, you break the old chain using either a quick link or a chain tool. You
then measure the new one against the old one for length or use our special length
checking method and reattach the new chain using either a quick link again or the
special joining pin, double checking before you do so that it’s threaded
correctly through the derailleurs. Now, two other mechanical processes that
can seem daunting but are in fact simple are replacing your bar tape and
re-indexing your gears so making sure that they work correctly. We’ve got videos
explaining how to do both those things and you can get to them just up there.
Before you leave this video though, do make sure you subscribe to GCN, because
we have a mechanical video out every week and you’re sure to need it at some point.