Sooner or later, any enthusiastic rider will have their bike chain come off or break completely. Luckily, you don't need to take your bike to an expensive repair shop to fix this common problem if you know what you're doing.
Steps
Method 1 of 2: Replace a Loose Chain
Step 1. Find the slip
Sometimes while riding, the chain will slip off the sprocket, but it won't break. Because the chain is still between the front and rear derailleurs in this case, no special maintenance is required. Usually all you have to do is put the chain back on its sprocket. When you experience chain slippage, get off the bike and try to identify it. Usually the chain will fall off the front wheel, but it will be stuck between both derailleurs.
Look for the places where the chain is stuck against the frame. These jams must be cleared before riding the bike again
Step 2. Use the quick release if the chain is stuck
Sometimes in the event of a slip, the chain will get stuck between the rear sprocket and the frame. In this case, it is a good idea to loosen the quick release and remove the nut to loosen the rear wheel from the chain. When you've loosened it enough, just pull the chain.
- Open the quick release by first pulling the small lever in the center of the rear wheel. Then loosen the wheel nut on the other side to loosen the “fit” that the rear wheel has on the frame. Once loosened, the chain should come off easily.
- Don't forget to re-adjust the quick release before riding the bike. You must close it completely. It should be tight, but not too tight to make movement of the chain impossible. If you feel it is too tight, loosen the wheel nut and try again. Similarly, if it is too loose, then tighten it.
Step 3. Loosen the chain if your bike has a rear derailleur
For bikes with rear derailleurs, simply loosen the chain and insert it around the front sprocket. On most bikes, the rear derailleur is spring loaded, so it keeps the chain tight while riding. Take advantage of this by pushing the rear derailleur arm forward to provide slack for the chain. Then use it to insert the other end of the chain around the smaller front sprocket. Release the arm on the rear derailleur and make sure the chain is tight.
From this point on, you can usually walk around again! The bike can shift erratically until the chain slips in the gear where it was when the slip occurred
Step 4. Turn the pedals on the bike without a derailleur
For bikes without a derailleur, grab the chain on the gear tooth when pedaling. Many bicycles (such as fixed gear or "fixies") do not have derailleurs. The easiest way to repair a loose chain in this case is to place the chain on the rear sprocket, hook as much of the chain as you can onto the bottom of the front sprocket, and carefully turn the pedal back. The chain should “catch” the top of the front sprocket. When the “caught” part reaches the top of the front sprocket, the chain should begin to slide through the bike's gears as usual.
Turning the pedals is easier if you raise the rear tire of the bike. To do this, you can place it on a stand or support the back of the frame with whatever material at hand. Alternatively, you can have someone help you hold the rear wheel so that it doesn't hit the ground as you put the chain back on, or you can turn the bike all the way around
Step 5. Pedal until the bike is in the correct gear
Get on the bike and pedal forward at a slow speed. If your bike has gears, the chain may go back to the gear where it was when the slip occurred. Otherwise, keep shifting the gear until pedaling is smooth.
Note: On fixed gear bikes, chain slippage can be particularly dangerous and troublesome, and is usually a symptom of a chain that is too loose. Consider adjusting the tension on the chain by turning the tire back before riding again
Step 6. Do some final checks
Before resuming normal riding, make sure you have comfortable gear. If your bike has it, change the gears on both the front and rear derailleurs until the chain turns smoothly without making any noise.
Method 2 of 2: Replace a Broken or Fallen Chain
Step 1. Buy a new chain and a chain cutter
To replace a bicycle chain that is broken or has fallen off completely, you will need to get a new chain to fit the bike, as well as a chain cutter to remove the old chain and secure the new one. You will also need a replacement bolt to connect the new chain, but this should come with it.
You can buy these items at a sporting goods store or bike store
Step 2. Assess the damage and try to repair it if possible
Stop riding the bike and put it on its side with the sprocket up. If the chain is still on the bike, look for the break. If the chain is hanging off the sprocket, then it will be easy to find the two separate ends of the chain. If the chain has completely fallen off, then you can start putting in the new chain. In most bicycle chains, each link is connected to the next by a metal bolt that goes through the outside of one link and the inside of the wheel of the adjacent link. Most bicycle chains fall into one of these 3 categories:
- Chains with special replacement bolts. These chains require a special type of bolt from the manufacturer (usually included when the chain is purchased) to repair a break. If you don't carry these special bolts with you when you ride, you may be out of luck in terms of repair options until you can get to a bike shop.
- Master link chains. These chains have a special link with two bolts that is used to join the two ends of the chain. If the link is broken, you may have to wait until you can replace it so you can repair the chain.
- Chains with "normal" bolts. Older, more traditional chains have uniform bolts, any of which can be used to repair a break (as long as you have a chain breaker).
Step 3. Remove the damaged chain from the bike
If you've decided that the chain will be easier to replace than repair, the first thing to do is get rid of the old chain. If the chain has split completely, simply turn the pedals until the length of the chain has passed around the chain wheel and can be removed. If the chain is still attached, you may need to break the chain to make it easier to remove. You can do it with a chainsaw.
- To use a standard chain tool, simply line up one link of the chain in the internal groove of the tool, securing it between the "teeth" on the tool. Then, turn the handle of the chain tool to position the tip down and push the bolt out of the chain. If you want to reuse the chain, make sure you only push the bolt far enough so that the two links can separate. Don't push the entire bolt all the way in, as it is quite difficult to control.
- Once you've made a break in the chain, simply turn the pedals to pass the broken chain through the bike's gears. Ideally, you want to buy a replacement chain that is exactly the same length as the chain you had before (although bikes with a rear derailleur allow a small margin of error), so now is a good time to count the links in chain. You should also take note of the type of drive train you have, as this determines which chains are appropriate. For example, 9-speed drive trains require 9-speed chains.
Step 4. Raise the rear tire
Then insert the new chain along the rear derailleur. You may have to turn the rear tire, which is much easier if it is off the ground. If you have a bike rack or garage wall hook that allows you to hang your bike with the sprockets pointing towards you, use it. If not, just support the back of the bike frame with wood, boxes, cinder blocks, or whatever else is around you.
Also take note of the derailleur arrangement. If the rear derailleur has a cable attached to the derailleur, shift to the highest gear (or the smallest sprocket, at the rear). If the front derailleur has a cable attached, shift to the lowest gear
Step 5. Pull the chain through the rear derailleur
The rear derailleur on a bicycle is the spring system of the gears that hang below the main rear sprocket on most modern bicycles. Properly inserting the chain through this derailleur is vital for a smooth and safe ride. Take the “female” end (that is, the end of the chain without a protruding bolt) of the properly sized replacement chain and insert it around the lower pulley. If done correctly, the chain should form a smooth, straight, backward “S” path through the derailleur. Make sure the chain is not snagged or resting on anything other than the pulley. If so, there will be a bump in the "S" back.
- There may be a small metal "tab" between the two small pulleys on the derailleur. The chain must pass this tongue without rubbing it.
- Some bicycles, such as fixed gear bicycles (or “fixies”) and bicycles with a gear shift mechanism, do not have a derailleur. In these cases, simply insert the chain onto the rear sprocket, turning the wheel as needed.
Step 6. Insert the chain into the rear cassette
On geared bikes, the cassette is simply a set of several sprockets attached to the rear wheel of the bike. If the chain is properly positioned along the derailleur, pull it up and over the smallest sprocket on the cassette. Make sure the chain is tight and correctly positioned along the rear derailleur and above the sprocket. Then, pull on it to get a little slack at the end of the chain.
Step 7. Weave the chain across the front derailleur
Most modern geared bikes have a metal mechanism near the front sprocket that moves to shift the chain from one front gear to another. Insert the front end of the chain along this front derailleur, turning the rear tire for more slack as needed.
Again, fixed gear bikes generally don't have a front derailleur, so just wrap the chain around the front sprocket
Step 8. Place the chain on the front sprocket
Align the chain with the smallest front sprocket. Stretch it out to fit tightly with the teeth on the front sprocket, and then position it around the sprocket, turning the pedals as needed to get enough slack.
Step 9. Connect the two ends of the chain
Finally, once the chain passes all the way through the gear system safely, you can join the two ends of the chain together and start riding again. Line up the "male" and "female" ends of the chain with a chain cutter (again, you can find this tool at all bike stores). Make sure the two ends of the chain rest firmly in the groove of the tool and are connected to the “teeth”. Make sure the bolt protrudes an equal distance from each side of the link, as even minor misalignment can cause structural weakness in the chain, which could lead to another repair.
- A helpful tip is to use a small, thin piece of metal called a "C-hook" to hold the ends of the chain close to each other. This makes the job much easier, as you won't have to worry about holding the chain in place and risk losing either end. In a pinch, a bent paper clip can substitute for a Type C hook.
- In some cases, if you connect a chain that does not use a master link, the pin you use to join the ends of the chain can cause the link to go taut. This can cause a lock or hard spot in the pedal's travel. To solve this problem, make the links on either side of the taut part follow a direction perpendicular to the way the chain turns (that is, diagonally).
Advice
- It is always important to learn basic chain repair skills. Not only will it save you from paying a mechanic to fix simple faults, but it will also save you the risk of being stranded far from the nearest service shop.
- If you can, buy a tool called a chain tensioner. This tool is useful for bikes that have a derailleur pad or multi-speed bikes converted to single gear. (A bike with derailleurs and a derailleur will already have a built-in tensioner.) Buy a pair and follow the instructions on the package. Generally, you will need a Phillips screwdriver or Allen key of a certain size. This tool is good for getting the correct chain fit.
- If you find that your chain is still loose and you do not have the service of a bicycle mechanic, you may need to remove the links from the chain to shorten it. However, only do it if you know what you are doing!
- If your bike chain falls off every now and then, it doesn't mean it's bad. However, if it continues to fall, it could mean that there is something that needs to be regulated by a bike mechanic.
Warnings
- If you have long hair, tie it up, as well as any dangling clothing and zippers before beginning any repair that involves bike chains.
- Make sure you don't put your fingers on the chain; otherwise, you run the risk of injuring and even cutting them.
- You may want to wear gloves, as your hands will get greasy while working with the chain.