The basic steps to thread and find a new chain
Putting a chain on your bicycle means threading it through the derailleur system and connecting the ends. Start by laying the chain over the smallest chainring at the front and the smallest sprocket at the back — this is the slack position that makes threading easiest. Feed the chain up and around the front chainring, then down and back through the rear derailleur cage, over the rear sprocket, and back toward the front. Once the chain is threaded, you connect the two ends using either a chain link (for chains with a removable link) or a chain tool (for chains that need to be riveted).
The entire process takes 10 to 20 minutes if you have the right tools and the chain ends are already prepared. If you are replacing a chain that broke, the old chain may have left the derailleur in an awkward position — shift to the smallest rings front and back before you start, which resets the derailleur arms to their most relaxed state.
Key Takeaways
- Thread the chain through the derailleur system with the bike in its smallest chainring and smallest sprocket position to minimize tension.
- Chains with a removable link (often called a master link) connect by hand; chains without one require a chain tool to push the pin through and rivet the ends.
- After connecting the chain, shift through all gears to confirm the derailleur moves smoothly and the chain does not rub.
- A chain that is too tight will strain the drivetrain and wear faster; a chain that is too loose will slip under load.
Threading the chain through the derailleur
Position your bike so you can see both the front and rear drivetrain clearly — a repair stand makes this easier, but you can also flip the bike upside down so it rests on the handlebars and seat. Shift the front derailleur to the smallest chainring and the rear derailleur to the smallest sprocket by turning the barrel adjusters or shifters until both are at their loosest position.
Pick up one end of the chain and feed it upward and around the front chainring, making sure it sits in the teeth. Bring the chain down and back toward the rear wheel, threading it through the upper pulley of the rear derailleur cage first, then under the lower pulley, and finally over the rear sprocket. The chain should now form a loop that goes around both rings and through both derailleur pulleys.
Check that the chain is not twisted and that it sits flat against each ring and pulley. A twisted chain will not shift smoothly and may slip off during riding. If the chain is twisted, unthread it and start again — it is faster than troubleshooting a misaligned drivetrain later.
Connecting the chain ends with a removable link
Many modern chains come with a removable link, sometimes called a master link or quick link. This link has a special design that lets you push the two sides together by hand without tools. Bring the two ends of the chain together so they overlap slightly, and slide the removable link onto both ends at the same time.
Push the two sides of the removable link together firmly until you hear or feel a click. The link should snap into place and hold the chain ends together. Tug the chain gently to confirm the connection is solid — it should not come apart under hand pressure. Some removable links come with a small clip that you snap on after connecting; check the instructions that came with your chain or link.
Once the link is connected, rotate the pedals backward a few times to make sure the chain moves smoothly through the entire loop. If the chain binds or makes noise at the connection point, the removable link may not be fully seated — disconnect it, check that both chain ends are aligned, and reconnect.
Connecting the chain ends with a chain tool
If your chain does not have a removable link, you will need a chain tool (also called a chain breaker or rivet tool) to connect the ends. A basic chain tool costs $15 to $40 and works by pushing a pin through the chain link to rivet the two ends together. Bring the two chain ends together so they overlap, and position the chain tool over the pin you want to push through.
Tighten the chain tool handle slowly and steadily, watching the pin as it moves through the link. Push the pin until it is flush with the other side of the link — do not push it all the way through and out the other side, or the chain will fall apart. Stop when the pin is level with the chain plate on both sides.
Remove the chain tool and check the connection by flexing the chain side to side at that link. The link should move slightly but not excessively. If the link feels stiff or the chain will not bend there, you may have pushed the pin too far — some chain tools have a second notch that lets you back the pin out slightly to free up the link. Rotate the pedals backward to confirm the chain moves smoothly through the derailleur and does not bind at the connection point.
Adjusting chain tension
A properly tensioned chain should have about half an inch of vertical play when you push up on it midway between the chainring and rear sprocket. Too much play means the chain is loose and will slip under load; too little means it is tight and will wear the sprockets and derailleur faster.
On a single-speed or fixed-gear bike, you adjust tension by moving the rear wheel forward or backward in the dropouts (the slots where the axle sits). Loosen the axle nuts or quick-release lever, slide the wheel back to tighten the chain or forward to loosen it, then tighten the axle again. Check the tension, and repeat until it feels right.
On a bike with a derailleur, the derailleur itself absorbs most of the chain slack, so you do not need to adjust the wheel position. Instead, check that the derailleur moves freely and that the chain has the right amount of play. If the chain feels too tight even with the derailleur in the slack position, the chain may be too short — you may need a longer chain or professional help to diagnose the problem.
Testing the chain after installation
Before you ride, shift through all the gears on both the front and rear derailleurs while rotating the pedals slowly by hand. The chain should move smoothly from one ring or sprocket to the next without hesitation, noise, or rubbing. Listen for grinding or clicking sounds, which usually mean the chain is rubbing against the derailleur cage or chainring.
Check that the chain does not rub on the derailleur cage when you are in the smallest chainring and smallest sprocket position — this is where the derailleur is most relaxed and rubbing is most likely to happen. If it does rub, the chain may be too long, or the derailleur may need adjustment. Shift to the largest chainring and largest sprocket and confirm the chain does not go slack or fall off.
Spin the pedals forward at a normal cadence and listen for any noise or grinding. The chain should be nearly silent. If you hear clicking or grinding, stop and check the connection point — the removable link or rivet may not be fully seated. After the first ride, check the chain tension again, because new chains sometimes settle slightly as the links flex.
Common mistakes and how to avoid them
The most common mistake is threading the chain incorrectly through the derailleur cage. The chain must go through the upper pulley first, then under the lower pulley — if you reverse this, the derailleur will not work and the chain may fall off. Before you connect the ends, trace the chain path with your finger from the front chainring all the way around to the rear sprocket and back to the starting point.
Another mistake is connecting the chain ends while the derailleur is under tension. If you connect the chain with the derailleur pulled tight (as it would be in a large chainring and large sprocket position), the chain will be too tight when you shift to smaller rings. Always connect the chain with the bike in the smallest chainring and smallest sprocket position.
Pushing the rivet pin too far through the chain link is also common and hard to fix. If you do this, the chain will fall apart the first time you ride. Use a chain tool with clear markings or a second notch so you know when to stop. If you are unsure, push the pin slowly and check the link frequently — it is easier to push a little more than to back out too far.
Frequently Asked Questions
Do I need special tools to put a chain on my bike?
A removable link chain requires no tools — you can connect it by hand. A chain without a removable link requires a chain tool, which costs $15 to $40 and is worth buying if you plan to maintain your own bike. Many bike shops will sell you a chain already cut to the right length and connected, which saves you the tool cost if you only need to do this once.
How do I know if my chain is the right length?
A chain that is too short will not reach around both the largest chainring and largest sprocket, or it will be too tight in that position. A chain that is too long will have excessive slack in the smallest chainring and smallest sprocket position. Most chains come pre-cut for standard bike sizes, but if you are replacing a chain, measure the old one or count the links and match that number.
What should I do if the chain keeps falling off after I put it on?
Check that the chain is threaded correctly through the derailleur cage — the upper pulley first, then the lower pulley. Confirm the derailleur is aligned and not bent. Shift to the smallest chainring and smallest sprocket and check that the chain has the right amount of slack. If the chain still falls off, the derailleur may need adjustment or the chain may be the wrong length for your bike.
Can I reuse an old chain or do I have to buy a new one?
If the old chain is broken, you need a new one. If the old chain is intact but dirty or rusty, you can clean it and reuse it. Chains wear over time and become stretched, which causes poor shifting and premature sprocket wear. If your bike shifts poorly or the chain skips under load, a new chain often fixes the problem.
How often do I need to put a new chain on my bike?
Most chains last 1,500 to 3,000 miles depending on how often you ride and how well you maintain the drivetrain. Keeping the chain clean and lubricated extends its life. You will know it is time for a new chain when shifting becomes sluggish, the chain skips under load, or you notice visible rust or damage to the links.