Watch: MTB Chain Repair Basics

Today, my bike is looking fly with a brand new gold chain. I installed this today because my old chain snapped at the bike park. Thanks to the help of a chain tool, I was back up and running. So why did I replace my chain if it was fixed? More importantly, how did I fix my old one? Today we’ll be talking about all of this, but first let’s take a look at some of the tools we use to work on chains.

This is a chain tool, or chain breaker. The spot on the end is for removing and joining links, while the spot at the back is for loosening tight links. To pop a link out, line it up at the end and crank down on it—carefully of course. A good chain breaker is measured to stop short of pushing the pin all the way out, but I recommend playing it safe and not going all the way to this point.

To join a link, put the chain in the opposite way and line up the pins. Of course, you need to stop pushing when the pin reaches the end. When you join a link, it’ll sometimes be tighter than the others. Use this part of the tool to push on the pin very slightly, which will loosen it up.

Since popping links in and out can weaken them, most chains have a master link for removal and maintenance. While there are special pliers made to pop these out, I don’t think most people have them. Most master links can be popped out by hand, and stubborn ones can be popped out carefully with pliers by squeezing the link end to end.

Through normal use, chains actually stretch out a bit. Eventually they don’t line up perfectly with your gears, and cause wear on your drivetrain. If you have good parts on your bike, it’s cheaper and easier to replace your chain every so often, than to get a new cassette, chainring, and set of derailleur pulleys. You could use this gauge to tell if your chain needs replacement, but just doing it on a schedule is better than nothing. For an average or casual rider, I’d recommend doing it at the beginning of each riding season. If you race, have expensive parts, or are particularly abusive, it may be a good idea to do it a few times per season, maybe even invest in a gauge.

So, let’s apply what we’ve learned with a real life scenario. You’re out on the trails and this happens. If you’ve never snapped a chain before, let me tell you it isn’t pretty. Your drivetrain suddenly goes limp, which can cause you to crash or smash your knee on the frame. At this point you’re either planning your long walk back to the trailhead, or reaching for your trusty multi tool. Brands like Park, Topeak, Crankbrothers, and Lezyne, just to name a few, have chain breakers built right into their multitools. While these are usually kinda clumsy to use, they’re better than nothing.

First let’s take this broken stuff off the chain. To join the chain, you can see here that we need to remove one more segment. Now we’re in business. Even though this chain is now short by one link, your derailleur just needs to reach forwards a bit to make up for it. To get home, this is fine, although you should replace your chain as soon as possible. After all, if you snapped your chain in the first place it probably needs to be replaced. Plus, at one link short you’re putting extra stress on your derailleur and drivetrain.

When reinstalling a chain, you’ll need to route it through the derailleur. If you’ve never done this before, it might be confusing, but you can always look at a friend’s bike for reference. Just start at the back of the cassette, route it in front of the upper pulley, and behind the lower pulley. Go around your front chainring, or even your bottom bracket to join the chain together.

If you’re replacing your chain you can always line it up next to your old one for size. If you repaired it out on the trails, just add an extra link to make up for the one you removed. If you don’t have your old chain, then measure it up so that your derailleur is angled slightly forwards in your lowest gear. Don’t go more than 45 degrees as this is probably going to be too short. Oh yeah one more thing… if you have gears up front, be sure to shift them into the largest ring while measuring.

So, what to do with your old chain? I say, use it for practice. You can even make a keychain. The practice will come in handy the next time you find yourself stranded miles from home. Thanks for riding with me today and I’ll see you next time.