In a recent Technique Tuesday, we discussed a quick solution to dropping your chain during a race. While the techniques listed are a great temporary way to get yourself out of a sticky situation, it won’t likely solve some of the deeper, mechanical problems that might be causing your chain to drop. In the first of a two-part article, we will examine some of the common problems that cause chains to drop and provide both solutions through adjustments or parts replacements.
Stay tuned for part two, where we will offer seriously habitual chain-droppers a list of extras and goodies including chain guards, watchers and single chainring options and certain derailleurs you can install on your bike to transform your sloppy drivetrain into a bulletproof setup.
Avoiding Situations Where Dropping the Chain is Common
Before we roll up our sleeves and head towards our work bench, the first item to assess is why our chain drops so frequently. The most likely answer to this is chaos. Cyclocross is a whirlwind of a sport where derailleurs get clogged with mud, bikes are flung onto our shoulders, and most of our components were designed with smooth road riding in mind. Even if your shop mechanic has the golden touch with your front derailleur, the well-adjusted derailleur cage won’t prevent your chain from dropping if the chain bounces from the bottom of your chainring. We’re not the only ones to have witnessed this either; more than a few commentators on our cowbell forum have noticed the chain bouncing off the chainring first.
There are a few situations that would cause a chain to bounce off the bottom of the chainring, causing the rest of the chain to drop. The first is more common with beginner or completely exhausted racers. When they are finished shouldering or carrying their bikes over a set of barriers, they don’t set their bike down, but practically just let go of the top tube, allowing their bike to slam against the muddy ground with their poor chain bouncing in every direction. In the second situation, a rider is confidently roaring down technical terrain or attempting to bunny hop an obstacle to get their feet in the right position. Pedaling your feet backwards in these cases, or just as bad, attempting to shift gears, are two ways you will likely drop your chain.
In both of these situations, practicing techniques after a little high intensity training, when your heart is at elevated levels, might put your time to better use than attempting to perform a million adjustments on your bike. Reminding yourself to gently set down your bike or picking the smoothest lines might provide the ticket. But remember, even seasoned racers with their perfectly tuned bikes often catch a rough break every once and again, even pros like Jeremy Powers:
Troubleshooting the Derailleur and Chain
If you are dropping your chain even in smooth situations, like when riding on pavement, there could be some mechanical problems that should be dealt with. If you take it into a bike shop, most mechanics are going to focus on two likely causes of a dropped chain.
The first is that one of the derailleur’s limit screws is too loose, allowing the cage to fall too far inward or allowing the derailleur cable to pull the cage too far outward. Adjusting limit screws are a fine art, but if you’re stubborn enough to want to DIY, make sure you identify the correct screw for which side the chain commonly drops from, and tighten by quarter turn increments. But if your derailleur’s limit screws were already set up correctly, this will likely end up only creating more chain rub with your cage and not solving the problem of a dropped chain.
The second likely problem a mechanic will focus on is the condition of your chain. A stretched chain is a likely culprit because the mismatch concerning the length between links and the teeth on the chainring will provide hesitant shifting or worse. If you find yourself riding single-track a few days of the week or filling up your weekends with cyclocross racing, you shouldn’t wait until you drop your bike off at a shop to learn that your chain has passed an acceptable stretching limit. Checking the stretch on a chain is a good weekly habit, and besides, chain checkers, like Pedro’s Chain Checker Plus, is one of the least expensive tools you can buy.
Cyclocross racers who power wash their bike and throw it in the garage for the next weekend of racing will likely have rusty and stiff links that could skip enough to drop a chain. On the other end of the spectrum, you have the riders who pour chain lube on pre-existing dirty lube, and their chains start to grow black and crummy. Usually this latter category has a more frequent problem of chain-suck, where the chain keeps riding up the front chainring because the friction of the dirt is stronger than the spring mechanism in the rear derailleur, but dirty chains can easily cause chains to drop as well. The solutions here should be easy enough. Dirty chains need to be degreased, stiff links need to be worked free and lubed, and stretched chains need to be replaced as soon as possible.
The last major culprit of the chain would be its length. Just because you have a brand new bike doesn’t mean you should just assume the chain length is correct. A chain that’s too long usually puts your rear derailleur in an unwarranted position where it can’t properly compensate for a chain sliding from the big and small chainrings. And a chain that’s too long will make it harder for the rear derailleur’s spring to keep even tension, especially on bumpy terrain, making it easier to derail.
Even if your chain is the right length, a common mistake is to try out your buddy’s wheelset, not realizing that his or her cassette is a much different range than yours. Usually this will either result in your rear derailleur protesting as you put it in the lowest gear or a high likelihood of a chain drop. If you have to try out your friends new Reynolds or Zipps, see if you can swap cassettes as well.
If the front derailleur and the chain are not the reasons behind your constant chain drops, perhaps your chainrings might be at fault. Nothing will drop a chain faster than a few bent teeth on a chainring, but worn teeth are not much better. If your once beautiful teeth are looking like crested waves, you might unfortunately need to invest in a new chain and chainrings. However, if you feel like nothing looks worn and your derailleur is set up perfectly, make sure to check the tension on the chainring bolts. The demands of cyclocross have a tendency to vibrate bolts loose, and on more than one occasion, I have worked on bikes with “chain-dropping” problems when I discovered that the whole chainring oscillated from side to side and allowed a partial rotation because the bolts either were not properly torqued to begin with or they vibrated out of torque. It also goes without saying, in the rigors of a cyclocross season, you can easily bend a chainring. Pedal backwards and make sure it’s completely true, and if not, find a replacement.
But as we mentioned before, cyclocross races are muddy, chaotic endeavors. If a dirty chain increases the chances of dropping your chain on a road bike, a drivetrain caked with mud is bound to give you a few headaches over an hour. Sometimes the best upgrade is a good friend who waits for you in the pits with a power washer. Still refuse to deal with dropped chains? Stay tuned for a future Mechanical Monday where we will lay out some of the upgrade possibilities to ensure your bike rarely sees a dropped chain even in the worst of conditions.