How to replace a chain — 14 easy steps to a fresh transmission

Chains wear out. If you're a strong rider or cover lots of dirty miles, it could wear out faster than you think. Allowing a chain to develop wear, effectively increasing the pitch, the distance between the rollers joining the links, will only wear out the sprocket and chainrings - the really expensive bits of your transmission. Save yourself cash in the long run by switching chains. Here's how you do it.

Our guide below shows you what we believe is the best method to replace a chain. We've included a list of the tools and materials that you will need to complete the job and, in some cases, where you can buy them. If there are others that you prefer then feel free to let everybody know in the comments.

Tools & Materials

You'll need:

•A new chain 
•A chain link-splitter tool 
•A new chain measure tool
•An old spoke
•Pliers

1. Does it need replacing?
The best way to check to see if your chain needs replacing, is to use a chain wear indicator tool. Hook the curved end of the tool against the rounded centre portion of a link roller and lay the tool along the chain. Add a little pressure to the pedals to pull the chain taut. The other (gauge) end of the chain wear indicator tool should stand proud (slightly on top of) the link below it. If this is the case, the chain is fine. You'll notice the tool has two markings at the gauge end '.75' the other '1.0'. If the .75 gauge end of the tool falls into the gap between the rollers it's a sign that your chain is wearing and replacement is recommended soon, if the 1.0 end is able to drop into the link, the chain is fully worn and should be replaced immediately.

2. Clean the chain
Working on a dirty of thing is no fun, even if it’s destined for the bin, so clean it up and do the chainrings and sprockets while you’ve got the suds in the bucket. There's no point in getting old gunge straight on the new chain, so cleaner the better. 

3. Drop the chain
Trying to split the chain or access and operate the master link while the chain is on the rings and under tension is tricky. Drop the chain off the chainrings. This will give you a decent loop of slack chain to work with.  

4. Locate the master link
This is a split chain link, a two part 'breakable' link used to make the splitting and joining of a chain an easier and more accurate job. It could be black, gold or silver depending on the brand of chain you use. All work the same way.

Locate the roller axle pins through the two rollers. Press the opposite sides of the Master link plates together and in opposite directions at the same time. The link plates should slide apart, though they'll sometimes need a bit of persuasion especially if the chain is dirty. A set of master link pliers makes this a lot easier.

5. Always keep the master link
Keep the old master link from the outgoing chain as an emergency spare even if the rest of the old chain is heading to the bin. We generally tape it to a bit of brake or gear cable, or sometimes under the saddle, so you never get caught without it. You'll be glad you did when you, or a fellow rider, breaks a chain while out on a ride. This is still a good idea, even if you use a Shimano chain that's joined by a pin.

6. Pin pusher
If your chain isn’t one that uses a master link, you’ll need to use a traditional chain splitter tool. Insert the chain into the recessed housing of the tool ensuring the links are exactly perpendicular to the tool's drive pin, to avoid damaging the edges of the holes. 

7. Screw finish
Screw the handle of the chain tool into the body of the tool, to allow the tool's drive pin to locate squarely onto the head of the chain’s link pin. When it’s all square, drive the link pin out. Don't be tempted to rush and mis-drive the head of the pin, as this can cause the hole in the outer link plate to be damaged and potentially make the fresh join less secure.

8. Un-thread the chain
The chain can now be unthreaded from the transmission. If you've never bothered to study the route the chain takes around the sprockets, chain rings, and jockey wheels of the rear derailleur do so before removal. Also don't forget to thread it through the front derailleur cage - we've seen it done when rushing. You'll need to get it right when you thread the new one back into the transmission. There is only one way that will result in functioning gears and forward drive.

9. Shorten the new chain
You'll now need to shorten the new chain to the length of the one it's replacing (assuming that was correct). To work out where the new chain needs to be split, thread the ends of both chains onto an old spoke; this allows you to hang them up (or lay out) to find the link that needs splitting. This new Shimano Ultegra comes with 116 links, the standard length. Most modern road bikes will require five or six links removing, depending on chainstay length and gearing. 

10. Rethread the new chain
Some Shimano 10-speed chains are directional and must be fitted with the Shimano logos on the outward face of the links. SRAM's AXS 12-speed chain is also directional, though if you've already managed to ear out one of those you're doing well!

Loop one end of the chain through the front derailleur, the other around the rear sprockets, over the top of the upper jockey wheel and behind the front chain deflector tab in the jockey cage and to the rear of the lower jockey wheel, and inside the rear chain deflector tab. The two loose ends can now be joined.

11. Fit the pin
Some Shimano chains use a special joining pin, with a snap-off pointed leader. Bring the male and female ends of the chain together, line up their respective pin holes and insert the pin into the chain. Only the pointed leader section is joining the chain. This must now be pushed home with the chain splitter tool. 

More recent Shimano chains come with a master link, so you just hook the two ends together so the master link is in the top run of chain, put the bike on the floor with the brakes on and stand on a pedal so the link clicks into place. Alternatively, use master link pliers.

12. Drive the pin home
Fit the chain tool to the chain in the normal way, to drive the new pin home. Ensure you're well lined up before cranking the chain tool handle. The new pin should slide home with ease, only the last millimetre or so will feel firm at the handle. You're looking to leave the tiny rim at the end of the new pin visible, the same as the other factory fitted ones on the other links. Over pushing the pin will result in the chain link jamming and potentially a chain failure.

13. Remove the leader
With the new link in position you'll need to remove the leader section. This requires a pair of pliers and a sharp angled twist of the wrist to break the leader free. These Park Tools cable cutters have a crimper behind the cutters that works well for the job. 

14. Free up a stiff link
Sometimes the freshly joined link will run free first time, but occasionally the new join will be a little stiff. This can lead to skipping gears. When this happens we usually use our thumbs to apply a little side pressure to the link, which usually frees the link so it runs and shifts smoothly.