All cycling enthusiasts must sooner or later face the breaking or "falling" of the chain of their bicycle. Thankfully, there is no need to take the vehicle to an expensive machine shop for this common problem that you can solve on your own if you know how to proceed.
Steps
Method 1 of 2: Replace a Slipped Chain
Step 1. Locate the slip point
Sometimes, as you pedal, the chain can go out of its way, but it won't break. As it stays threaded around the front and rear sprockets in this case, no special maintenance is required - just put it back around the right chainring. When the chain "falls", get off the bike, place it on the ground with the sprocket facing up and inspect the damage. Typically, the chain comes off the front sprocket, but remains threaded through both derailleurs.
Check to see if the chain has been damaged after being squeezed against the frame - if so, you will need to repair it before getting back in the saddle
Step 2. Use the quick release mechanism if the chain is damaged
When it falls, it sometimes gets stuck between the frame and the pinion. If so, it's worth loosening the rear wheel quick release mechanism and removing the nut to free the chain. Once the wheel is loosened enough, simply lift the chain up.
- Open the mechanism by first pulling the small lever located in the center of the hub. Loosen the nut on the opposite side that "secures" the wheel to the frame. At this point, you shouldn't have any trouble freeing the chain.
- Don't forget to tighten the mechanism before resuming your bike ride. You should be able to close it completely - it should be tight, but not to the point where you can push the lever all the way down. If it feels too tight, tighten the nut less and try again. Conversely, if you feel it is loose, tighten it more.
Step 3. Loosen the chain if your bike is equipped with a rear derailleur
For models that have this mechanism, you just have to loosen the chain and bring it around the front sprocket. Typically, the rear derailleur is mounted on a spring that holds the chain in tension as you pedal. Take advantage of this feature by pushing the arm forward to make the chain slack. Next, wrap the other end (no longer under tension) around the smaller front crown. Release the arm and check that the chain is taut.
At this point, you can simply get back in the saddle! The bike may shift gears randomly for a while, until the chain resets itself on the sprockets it was on before the slip
Step 4. Rotate the pedals on bikes without a derailleur
For models that do not have this mechanism, you can return the chain to the sprocket by turning the pedals. Many bikes, such as fixed gear, do not have derailleurs. In that case, the easiest way to fix a loose chain is to hook it onto the rear sprocket, hook it as far as possible with the lower teeth of the front ring, and carefully rotate the pedals backwards. By doing so, the chain should be "captured" and begin to rotate around the front chainring. When the links fit into the upper teeth of the ring, the chain is back in place and runs normally.
It is easier to turn the pedals if you lift the rear wheel off the ground. To do this, you can place the bike on a stand or lift the rear area of the frame with whatever material you have available. Alternatively, ask a helper to lift it while you put the chain back in place or flip the bike over
Step 5. Pedal gently forward until the chain settles in the correct ratio
Saddle up and pedal forward at low speed. If your model is equipped with a derailleur, the chain should "snap" to the sprocket it was on before the slip. If not, keep changing until the pedals turn smoothly.
Note: on fixed gear bikes this problem is particularly dangerous and problematic, it often indicates that the chain is too loose. Consider adjusting the tension before riding the bike again
Step 6. Perform final checks
Before resuming pedaling as usual, make sure you have set a comfortable gear shift. If the bike has multiple gears, adjust both the front and rear until the chain runs smoothly again without making any noise.
Method 2 of 2: Replace a Broken or Missing Chain
Step 1. Get a new chain and a chain tool
To replace this piece that has broken or has completely detached from its place, you must have a spare suitable for the bike and a chain tool to remove the old one and mount the new one. You also need a pin to close the chain, but it usually comes with the spare you buy.
You can find these tools at a bicycle or sports equipment store
Step 2. Assess the damage and try to repair it if possible
Stop and place the bike on the ground with the sprocket side facing up. If the chain is still on the bike, check to see if it is broken. If you notice it dangling loosely from the crown, you shouldn't have a hard time locating the two ends that have separated. If, on the other hand, it has completely fallen off the sprockets, you can start assembling the spare part immediately. In most cases, each link of the chain is connected to the next by a metal pin inserted in the external "plate" of one link and in the internal "roller" of the adjacent one. Most bike chains belong to one of these three categories:
- Chain with special spare pins. In this case, you must obtain a special pin from the manufacturer (it is usually sold with the replacement chain) in order to repair the damage. If you don't carry these items with you when riding your bike, you may not be able to change the chain until you reach a repair shop.
- Chain with false link. This model is equipped with a special link with two pins that allows you to join the two free ends. If the false link breaks, you must wait until you have a spare to repair it.
- Chain with "normal" pins. The older, more traditional models come with links with all the same pins, which you can use to repair the break (as long as you have the chain tool handy).
Step 3. Remove the damaged chain from the bicycle
If you've decided it's easier to replace than repair, the first thing to do is get rid of the old chain. If it has opened completely, simply rotate the pedals until it is completely out of the sprocket. If, on the other hand, it is still a closed loop, you have to break a link to be able to disassemble it. You can do this thanks to the chain tool.
- To use a standard chain tool, simply align a link to the internal notch you see on the tool, taking care to lock it with the "tooth" of the tool itself. Then rotate the handle to lower the tip of the chain picker and push the link pin out. If you want to reuse the chain, push the pin just enough to separate the two links, but don't pull it out completely, as it's not easy to reinsert.
- When the chain is open, turn the pedals to slide it through the gears. In theory, you should buy a new one of the same length (although bikes with a rear derailleur allow for a larger margin for error); at this stage it is therefore advisable to count the number of links. You should also make a note of the type of transmission used on your vehicle, as it determines the suitable chain types. For example, a nine-speed transmission needs a nine-speed chain and so on.
Step 4. Lift the rear wheel
Slip the new chain into the rear derailleur. The rear wheel may need to be rotated, which is easier to do if it does not touch the ground. If you have a kickstand or hook on the garage wall that allows you to lift the bike with the sprocket facing you, use it. If you don't have it, you will just have to lift the back with some wood, boxes, cinder blocks or any other similar object at hand.
Also pay attention to the arrangement of the derailleur. If the rear one has a cable that connects it to the shift knob, place it in the highest ratio. If the front derailleur also has a shift cable, set it to the lowest gear
Step 5. Pull the chain through the rear derailleur
On most modern bikes with shifters, this is a spring mechanism with sprockets that "dangles" under the main sprocket. To get a smooth and safe ride, it is necessary to correctly pass the chain through this system. Take the "female" end (the one with the link without a pin) of the appropriate spare chain and thread it through the lower crown; then, bring it up and around the top pulley. If you go right, the chain should run smoothly following an "S" path back inside the derailleur. Check that it does not get stuck or that it does not rest on other elements than the pulleys; if not, you should notice a bulge in the "S".
- There may be a small metal "tab" between the two derailleur pulleys. The chain must pass it without touching it.
- Some bicycles, such as fixed gear and hub gears, do not have a derailleur. In this case, simply thread the chain around the rear sprocket, as indicated in the next step, turning the rear wheel if necessary.
Step 6. Bring the chain to the rear sprocket set
On bicycles equipped with gears, the sprocket set is nothing more than a series of sprockets connected to the rear wheel. Once the chain is properly threaded into the front derailleur, pull it up and around the smaller sprocket. Make sure it is tight and positioned correctly in both the derailleur and over the cog and then pull it for some play.
Step 7. Pass the chain through the front derailleur cage
Most modern bicycles with different gears have a mechanism near the front sprockets that allows you to move the chain from one gear to another. Thread the end of the chain through this mechanism, turning the rear wheel for more "rope" if needed.
Remember that even in this case the fixed gear bikes do not have a front derailleur and you just need to slide the chain around the chainring, as described in the next step
Step 8. Bring the chain around the front gear
Line it up with the smaller diameter one, stretch it until it is tight and engages the teeth of the front bezel. Pull it around the sprocket by turning the pedals as needed for more play.
Step 9. Connect the two ends of the chain
At the end, when the chain has passed correctly through the entire gear system, you can join the two ends and resume your bike ride. Line up the "female" link with the "male" link on the opposite end and join them together using the chain tool (available at bike shops). Check that both links rest securely in the groove and that they are hooked to the "tooth" of the tool. Rotate the handle to bring the pin inside the chain by connecting the two links. Make sure it protrudes evenly from both sides, as even the smallest misalignment can cause structural weakness in the chain, requiring another repair.
Useful tip: use a small tool with a C-shaped hook, which allows you to bring the two ends of the chain together and hold them in place. In this way, the work is simplified and you do not have to worry about keeping the shirts in place, with the risk of them slipping. A simple paper clip can replace this tool
Advice
- If possible, purchase a tool called a chain tensioner. Buy a pair and follow the instructions on the package. Typically, you will need a Phillips screwdriver or Allen wrench of a certain size. This tool is perfect for being able to correctly tension the chain.
- It is always important to have the basic knowledge to repair the bicycle chain. Not only do you not have to pay the mechanic for small damages, but you avoid being stranded several kilometers from the nearest mechanical workshop.
- If you realize that the chain is still loose and you can't go to a mechanic who specializes in bicycles, it may be necessary to remove a few links to shorten it. Proceed with this operation only if you are capable!
- If the chain falls off the sprockets from time to time, it doesn't mean your bike is in trouble; however, if it is a problem that is repeated often, it could indicate that the vehicle needs mechanical intervention.
Warnings
- Be careful not to put your fingers in the chain, as you risk injury and even amputation of the finger.
- Tie your long hair, dangling clothes, and zip the zippers completely before making any repairs to the bicycle chain.
- If possible, you should wear gloves, as your hands will get a lot of grease.
