Tech Talk

Welcome to a new feature here on TheSeatPost: Tech Talk Tuesdays!


We'll be featuring tech tips from your favorite mechanic(s) on all sorts of topics, from new technologies, hot trends to trail-side repair and routine maintenance.




Today's Topic: Broken Chains

First of all, broken chains are mostly caused by poor shifting technique. During a shift under load (like when climbing a steep hill or when starting off in too high of a gear), chainring teeth and chain links can become deformed, bent, and/or damaged. This doesn't always (or even usually) cause the chain to break right away, though shifting quality both front and rear will be adversely affected. Rather, these will become weak pieces of the drivetrain that will fail at that least opportune moment sometime in the future, most likely near the finish of an important event or at a point in the ride many many miles from the nearest road/phone/car/house etc.

So the first tip is, as always, use preventative maintenance and proper technique. Keep your chain well lubed, and ease up on the pedals when you shift front or rear. As a general rule of thumb, use an easier gear than you think you need and shift before you need to.

But, too late, you were really jamming up that hill and went searching for that extra gear and now you've broken your chain! What do you do next? Reach for your chain tool! You do have a chain tool, right? right? If you answered yes to one of the previous two identical questions, keep reading. If not, skip to the section that starts with "You Unprepared Goof". So you brought your chain tool! good for you. Do you know how to use it? No? Well, read on. The idea is to remove the broken link, and reconnect the chain in a usable fashion. Here's how:

First, take a deep breath and relax. This'll go a lot better if you're calm and focused than if you're shaky and panicky.

1) Locate the offending link. Usually an outside plate of the chain will peel off and get jammed in your chainrings, cogs or derailleur. It make take some force to get the chain out, so try to pull strait out so as not to further damage your chain. This is also a good time to look for other damage that may hinder your ride even after you fix your chain.

2) Inspect the break and determine how many links will need to be removed. These include any frozen, broken, or twisted links. Use your chain tool, with the chain firmly against the stop, to push the chainpin most of the way out of the side of the chain at each end of the offending links. Do not push the pin all the way out because it is very, very difficult to get one back in. Leave the pin so it just holds the chain together. You may then have to put gentle side pressure on the chain to get the links to come apart. Be careful to remove links so that both a pair of outside plates and inside plates remain.

3) Make sure your chain is routed properly through your derailleurs. Forgetting to do this will invariably cause frustration and is very likely to also cause damage.

4) Reconnect the chain. Carefully line up the inner and outer chain links, again being careful to have the chain firmly against the stop on the chain tool. Next, slowly begin to push the pin into the chain, checking every few millimeters to make sure that it is going in strait. Push it until it just begins to protrude through the other side of the chain. This may leave the link tight, in which case you can apply moderate side force on the chain to loosen the taught link. You can also use the second set of holders on your chaintool (if it has them. some small ones such as the Park Tool CT - 5 have them, but most chain tools that are part of a multi-tool do not) to loosen up the link.

5) Pedal the bike into a decent gear and go!

You Unprepared Goof, you don't have a chain tool. Way to go. You probably wouldn't know what to do with one if you did. Do you have a buddy who does and knows how to use it? Great! Whenever possible, utilize this course of action. That way when it breaks again, you can blame that person.

Okay, so you're alone in the woods with no one around for miles and your chain is broken. Eff. But you're not totally SOL. You can actually take rocks and bang that chain back together. I've done it before and you can limp out of the woods a lot more often than you'd think.

Whichever of these techniques you employ to fix your chain, be sure to treat it as a temporary fix. However, there is another faster, simpler, safer, semi-permanent solution to your problems. It takes more planning, but if you're already planning on carrying your chain tool with you, you're 90% of the way there.

For another great explanation, with photos, check out Park Tool's own HowTo

This is something that has allowed me to fix a broken chain during a race in under a minute, and help dozens of other racers and riders repair their chains quickly and safely out on the road and trail.

1) Go to your local bike shop
2) Purchase a SRAM or KMC reusable quick link. I find that a 9-speed KMC or SRAM link will repair any 9 or 10 speed chain and work safely in your drivetrain.
3) Attach it to your chain tool
4) Go ride!

The quick link saves you the hassle of using the chain tool to reconnect the chain and the risk of a bad connection that goes along with it. Also, since it is a strong, new connection, you can treat it as a semi-permanent solution. You may want to do this if you have a worn drivetrain and a new chain would cause moderate or severe shifting and power transfer problems.

Thanks for reading.