The basic steps to rechain your bicycle
A chain that has fallen off your bicycle is usually fixable in under five minutes without tools. The chain most often comes off when you shift gears roughly, hit a pothole, or the chain has stretched over time. To put it back on, you need to position the chain onto both the front chainring (the large gear near the pedals) and the rear sprocket (the gears on the back wheel), then spin the pedals backward to seat it properly.
The process works the same whether your bike has one front gear or three, and whether the rear has five sprockets or eleven. The only difference is which front gear and rear gear the chain should sit on when you're done — but that comes after the chain is back on.
Key Takeaways
- Shift to the smallest front chainring and smallest rear sprocket before you start, so the chain has the least distance to travel.
- Thread the chain onto the front chainring first, then onto the rear sprocket, making sure it sits in the teeth of both gears.
- Spin the pedals backward several times to pull the chain tight and seat it fully into the gear teeth.
- If the chain still won't stay on after you've reseated it, the chain may be stretched or damaged and may need replacement.
Shift to the smallest gears before you start
Before you touch the chain, move the gear shifters so the chain is positioned on the smallest front chainring and the smallest rear sprocket. On the left shifter (front), this usually means pushing the lever all the way forward or pulling it all the way back — the direction depends on your bike's brand. On the right shifter (rear), turn the lever or push the button until the chain moves to the smallest sprocket in the back.
This step matters because it gives the chain the shortest path between the two gears. A chain that has fallen off while you were in a large front gear and a large rear gear has to travel a much longer distance, making it harder to thread back on by hand. Starting small makes the job faster and reduces the chance the chain will slip off again as you're working.
Thread the chain onto the front chainring
Look at where the chain currently sits. If it has fallen completely off, pick it up and hold it loosely in your hand. Position the chain so it wraps around the smallest front chainring — the gear closest to the frame, near the pedals. Push the chain onto the teeth of that gear, making sure it sits in the grooves and doesn't just rest on top.
You don't need to thread the entire chain at this stage. You only need enough of it on the front gear so that it won't slip off when you move to the next step. The chain should form a loose loop from the front chainring down toward the rear wheel.
Thread the chain onto the rear sprocket
Now guide the chain down and around to the smallest rear sprocket — the smallest gear in the cluster on the back wheel. Push the chain onto the teeth of that sprocket, making sure it sits firmly in the grooves. The chain should now form a complete loop: from the front chainring, down and around the rear sprocket, and back up to the front.
At this point the chain will be loose and may sag. That is normal. Do not worry if it doesn't look tight yet — the next step will pull it into place.
Spin the pedals backward to seat the chain
Grip the pedals and spin them backward (toward you if you're standing on the right side of the bike). Spin slowly and steadily for three to five full rotations. As the pedals turn, the chain will be pulled through the gears and will tighten itself. You should feel the chain catch and seat into the teeth of both gears.
Stop spinning and check that the chain is now tight and centered on both the front chainring and the rear sprocket. The chain should not be sagging, and it should not be rubbing against the frame or the derailleur (the metal arm that guides the chain). If the chain looks centered and tight, you're done — shift back to your normal gears and ride.
What to do if the chain won't stay on
If you've reseated the chain and it falls off again within the first few pedal strokes, the chain may be stretched or damaged. A stretched chain no longer grips the teeth properly and will slip off under load. You can test this by pulling the chain away from the front chainring — if you can pull it more than about half an inch away from the gear teeth, the chain has stretched and needs replacement.
Another cause is a bent derailleur, which throws off the alignment of the chain as it moves between gears. If the derailleur arm looks bent or twisted compared to the other side of the bike, that will also cause the chain to slip. A bent derailleur usually requires a replacement or professional adjustment.
If the chain appears undamaged and the derailleur looks straight, the problem may be that you're shifting gears too roughly or too quickly. Shift more slowly and deliberately, and avoid shifting while you're pedaling hard uphill.
Frequently Asked Questions
Do I need tools to put the chain back on?
No. Putting a chain back on requires only your hands. You do not need a wrench, screwdriver, or chain tool. If the chain is stuck or will not move, a tool may help, but the basic task is done by hand.
What if the chain is twisted or tangled?
Gently untwist it by hand before you thread it back onto the gears. If it's badly tangled, you may need to remove it completely — most chains have a master link (a special link that looks different from the others) that you can open by hand or with a chain tool. Once untangled, thread it back on using the steps above.
Can I ride the bike right after I put the chain back on?
Yes, once the chain is seated and tight. Spin the pedals backward a few more times to make sure it's fully caught, then shift through all your gears once to confirm the chain moves smoothly. If it does, the bike is ready to ride.
Why does my chain keep falling off even after I put it back on?
A chain that falls off repeatedly usually has one of three causes: the chain is stretched, the derailleur is bent, or you're shifting gears too roughly. Check the chain length by pulling it away from the front gear. If it stretches more than half an inch, replacement is the fix. If the derailleur looks bent, it needs adjustment or replacement.