Chain manufacturers attempt to make all of their links equally strong, but a chain is only as strong as its weakest part. The problem is, chains often consist of about 400 moving parts. Fixing a bike chain is a routine task that you should be able to accomplish in a few minutes whether on the road or trail or in the garage.

Fixing a Bike Chain – Chain Breaker and Master Link

Before fixing a bike chain, you’ll need one tool in particular; a chain breaker, if you don’t already have one in your saddle bag and a master link that fits your chain. Note that some chains come with their own master link included with the purchase.

Fixing a Bike Chain – Get the Length Right

If you’re simply fixing a bike chain, you don’t have to worry about chain length. Simply remove the broken link, and replace it with a master link, sometimes referred to as a power link, or missing link, depending on brand. If you don’t have a master link, you can just remove the broken link, and reinsert the pin provided you don’t push the pin all the way out the other side.  If you’re replacing an old chain with a new one, count the links in the old chain, and use the chain breaker to remove links on the new chain so that they both have the same number of links.

Steps to Fixing a Bike Chain

1. First locate the broken link. There should be two plates that are loose, and flapping around or a link that has a bend in it. These are the ones that get removed. You do not need to remove the chain from the bike. Keep the chain threaded through the derailleurs if you can as it will save you time.
2. Examine the chain breaker tool. You’ll notice a circular cradle that the push-pin moves through. Rest the link in this cradle where the pin lines up with the push-pin of the link you’re removing.
3. Turn the push-pin to push the pin through and out the other side. If you’re using a master link, you will need to have both ends of the chain an inner link as the master link is an outer link. If you don’t have a master link or another connector pin, do not push the pin all the way out the other side of the chain. Leave it so the pin is over enough to remove the inner link but not so far that it falls out. This will be important in the next step. Now do the same one full link removed, one inner link followed by one outer link or vice-versa, from the pin you just pressed out with the broken link being in-between.
4. If you removed the chain from the derailleurs, thread it back through being sure that it’s going the right way. Then place the chain in the smallest gear in the back and rest the chain to the inside of the chain rings on the front against the bottom bracket to give enough slack.
5. Now install the master link if using one through both the inner links and lock into place. If you have a connector pin, line up the ends of the chain and press that through breaking off guide end with your chain tool. If using the same pin that you just pushed out and left on the outer link, line the end up and push the pin back in. You want it so both sides of the pin are flush with the outer plate of the chain. If you pushed the pin too far through when you were removing it, line the chain up in the chain tool and set the pin on the resting plate to then press the pin in. It may be a bit off at first but it should line up as you continue to push it through the hole.
6. That’s it. The link with the pin you just installed may be a bit stiff but if you bend it laterally slightly with your fingers, it should loosen up to where you can’t even tell which link it was. The chain is now one link shorter, unless using a master link, but will still be good to go.
7. One note is that reinserting a pin is now the week point of the chain. When you do make it home, take out that pin and put in a connecting pin which will better strengthen the chain. The problem is you may not be able to tell which link it was so it’s recommended that you replace the entire chain.

Fixing a Bike Chain – Why Chains Break

One of the most common reasons for chain breakage is bad closure at the factory. With hundreds of thousands of parts going through, it’s inevitable that pins fail to center properly. The giveaway is a bulge on the inside of the outer plate that indicates that the end of the pin being pushed through wasn’t lined up, and bent the plate before going through the hole. This can also occur after you’ve ridden the bike for a while. Keep an eye out for this, even on brand new chains.

Bad Gear Combinations

Chains rarely break while in a straight line. The energy is evenly dispersed across the links while pedaling normally, even under load. Chains typically break when using extreme gear combinations, like big front to big back or little front to little back, also known as cross-chaining. The force is temporarily focused to a few links, slightly diagonal to each other, as the chain moves from one cog to another. Cross-chaining bends the chain, and it’s a recipe for snapping chains.

Chain Suck

Chain suck occurs when downshifting under load to a smaller chainring. The bottom of the chain doesn’t  disengage from the larger ring and gets carried upward (sucked up,) and wedges between rings and snaps. Chain suck is commonly caused by bent chainring teeth, dirty chains, or occasional burrs on the teeth of new chainrings.

Listen and Feel

If you hear or feel a regular click or your chain hangs up each and every revolution, it could mean that one of the pins has come loose on one side, allowing the link to bulge slightly to the side. The chain hasn’t broken yet, but it’s too wide to fit through the cage on the bottom of the derailleur. As it passes through the bottom of the guide, the leaf ticks or, in worst case scenario, hooks the side of the derailleur and locks up.

Bad Shifts

Broken chains, when in good working condition, are really not that common and are almost always the result of putting load on the chain when it’s not fully in gear.

Let Up

Experienced riders intentionally “let up” on the pedals during the shift when under hard effort such as hill climbing or sprinting. This has two effects, the first being less stress being placed on the chain and the second being simply more efficient and responsive shifting. Even top-of-the-line Dura-Ace drivetrains don’t shift well under load.

Fixing a bike chain isn’t too difficult of a task and can save you when out on the road or trail otherwise stranded. If doing longer rides farther from home, you should be able to fix a broken chain as easily as being able to fix a flat. Both leave you on the side of the road but if you know how to fix them, you’re home free.