How to replace your chain and sprockets featured image
Advice & Guides

How to replace your chain and sprockets

9 Apr 2020
Your bike relies on a healthy relationship between your chain and the teeth on the sprockets to lay down power. Here's how to restore harmony...

Imagine trying to eat steak and chips while wearing a gumshield. You might get it done… eventually, and you should expect a dose of indigestion later. You’re asking your bike to do something similar by running it on a worn chain and sprockets.

Seized chain links dragging their sloppy rollers over hooked sprocket teeth is a waste of energy that needs sorting. Here are the crucial steps in replacing chain and sprockets yourself…

1. Get the right bits

Do some digging on your bike – count the sideplates on the chain and multiply the number by two to get the number of links. Check the number of sprocket teeth, which should be marked on each. You could stick with what you know, but now is the time to consider whether to change the way your bike accelerates. Fitting a smaller front sprocket and/or bigger rear sprocket increases acceleration and doing the opposite reduces the rate of acceleration. The easiest way to get friskier performance is to drop a tooth on the front sprocket, which has the same effect as adding three teeth to the rear. While you’re ordering replacement parts, get a new tab washer for the front sprocket nut.

2. Got the tools?

You’ll need a chain tool to split the rivet link on your existing chain and reinstall a new one, and sockets big enough to remove your front sprocket nut and rear wheel spindle nut. If you rely on your bike for transport, find out the sizes and source the sockets before you remove any parts and leave yourself stranded.

3. Let’s go…

First job is to remove engine covers to gain access to the front sprocket. If this means removing the knuckle from the gear linkage then check first for a mark to show where the join needs refitting later. If there isn’t one, make a mark so you can put the knuckle back in the right place.

4. Slacken up front

Knock back the tab washer holding the front sprocket nut firmly in place. Wedge a small drift between the flat of the nut and the edge of the tab washer, and tap it with a hammer until it’s clear enough to let you get a socket over the nut. Next loosen the front sprocket nut, which is ideally done with an electric impact driver like the one in our pictures. If not, get a friend to sit on the bike while you undo the nut with as long a ratchet handle as you can muster, or a breaker bar. Leave the sprocket in place and the nut finger-tight.

5. Out with the old

With the chain still intact, slacken the nuts holding the rear sprocket to the carrier. Now use an angle grinder to grind off the protruding ends of the pins on one of the links on the chain you’re replacing. The instructions for your chain tool might tell you there’s no need to do this, but it’ll reduce the amount of strain on the tool at the next stage. Once the pin ends are gone, use the chain tool to push them through the rollers, which will split the chain in two and allow you to feed it past the front sprocket and remove it from the bike.

6. Sprockets off

Remove the front sprocket nut and slide off the sprocket and the tab washer behind it. Slip your new tab washer into place, then your new sprocket and finally replace the nut, tightening it by hand for now. Remove the rear wheel from the bike, take off the sprocket retaining nuts and sprocket before fitting the new one and refitting the sprocket nuts. Reinstall the rear wheel.

7. In with the new

Feed the new chain over the front sprocket and pass it through to the rear sprocket, pulling the two ends together on the rear sprocket teeth. Open the packet holding the rivet link supplied with the new chain and slide two of the supplied O-rings over the pins of the joining link. Now feed the joining link’s pins between the loose rollers at either end of the new chain, starting at the rear side of the chain so the ends protrude towards you. Slide the remaining two O-rings over the rivet link’s pins and push the sideplate over as much as it will go by hand.

8. The strongest link

Now use the chain tool to push the sideplate over the pins until it’s at the correct tension. This is the tricky part, compressing it by enough to secure it in place without overtightening and creating a tightspot in your chain. You want enough clearance between rollers and sideplate to be able to just slide a Stanley knife blade between the two and take it out again.

9. Change your pin

The final chain installation step is to peen over the ends of the pins to make certain the sideplate can’t slide off and cause the chain to come apart. Your chain tool may have a tool that can be driven into the end of the pin so the metal splays out and creates a lip to stop the sideplate sliding past. Alternatively, striking it with a small hammer should round the end and create the lip.

10. Tension’s increasing

Adjust the chain tension to bike manufacturer specifications and check the rear wheel is aligned . Tighten the front sprocket nut to manufacturer torque settings and knock over the washer tab to secure it in place. Double-check you’ve tightened all bolts correctly before replacing the sprocket cover and refitting removed parts such as the gear linkage.

11. Final fling

Give the chain tension a last check before giving the chain some lube if necessary (some chains come pre-greased and don’t need lubing until it’s worn off). Now you should be good to for another 10-20K miles, depending on how well you keep your chain clean, lubricated and adjusted.