How to replace a bike chain — simple steps to a smooth transmission

Chains wear out over time, and if you're a strong rider or frequently tackling dirty miles, it could wear out faster than you think. When a chain wears, it stretches, and its pitch - the distance between the rollers - becomes elongated. This accelerates wear on the sprockets and chainrings, which are costly components of your drivetrain. To save money and keep your transmission running smoothly, it's a good idea to replace your chain before significant wear sets in. Here's how to 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. If there are others that you prefer then feel free to let everybody know in the comments.

What tools and materials do you need to replace a bike chain?

• New bike chain 
• Chain link-splitter tool 
• Chain wear indicator tool 
• Quick link (if applicable) 
• Pliers 
• Cleaning supplies 
• Gloves

Step 1: Check if your chain needs replacing 

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Chains have specific wear limits depending on their speed. For chains that are made for an 11, 12 or 13-speed cassette, replace the chain when elongation reaches 0.5%. If it stretches to 0.75% or more, you'll likely need a new cassette as well.

For some 10-speed chains, replacement is typically needed at 0.75% elongation. If the stretch reaches 1%, the cassette will likely need replacing too.

The best way to check 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.

Step 2: Drop the chain or remove rear wheel

Trying to split the chain or access the quick link while it’s on the chainrings and under tension can be tricky.

Either drop the chain off the chainrings to create some slack or remove the rear wheel to make the process easier.

Step 3: Locate the quick link or use a chain splitter tool 

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 quick 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 quick link pliers makes this a lot easier, particularly on a worn chain. 

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Note: Keep the old quick 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. 

If your chain isn’t one that uses a quick 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. 

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.

Step 4: 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.

Step 5: 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). Don't measure the new chain against the old chain as it will have stretched. Instead, count the number of links and then take off the extra links on the new chain using a chain tool. 

Most modern road bikes will require five or six links removing, depending on chainstay length and gearing. 

Step 6: Clean your drivetrain 

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Before fitting your brand-new chain, take the time to thoroughly clean the rest of your drivetrain.

Focus on the cassette, jockey wheels, and chainrings, as there's little point in transferring old grime onto a fresh chain. A cleaner drivetrain ensures smoother operation and prolongs the life of your new chain, so the cleaner the better. 

Step 7: Re-thread 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. 

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.

Option 1: Using a quick link 

If your chain has a quick link, you hook the two ends together and position it in the top run of the chain. To lock the link, 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. 

Option 2: Using a joining pin 

Some 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. 

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.

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. Some cable cutters have a crimper behind the cutters that works well for this job. 

Step 10: 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.