You’re riding hard in the big chainring toward a steep climb. You push to keep your momentum going as long as possible, but finally you’re forced to shift to the small ring. Oops! The chain overshoots and falls onto the frame. You’re dead in the water, wildly turning the cranks with no resistance.
Later, the opposite happens. You’re spinning in the small chainring and need a bigger gear. But your shift to the big ring sends the chain over the top. Now it’s flopping around the crankarm.
Throwing a chain is usually the result of a badly adjusted front derailleur. That’s the first thing to correct if it’s happening frequently. But even properly adjusted equipment can goof if you’re pedaling too hard or too fast while shifting.
The chain can skip off the inside ring or you can experience the opposite problem — it won’t move off the big ring at all. That happens when there is so much tension on the chain that the derailleur can’t pull it from the teeth. The solution is simple: Reduce pedal pressure a bit just as you make the shift.
What To Do If You Throw a Chain
Shift the chain back on. Gently! No matter what causes the chain to fall off, you may not have to stop and get your hands greasy putting it back on. While still rolling, turn the crank easily and shift the front derailleur in the appropriate direction. The chainring teeth should catch the chain and set it back in place. Stop pedaling instantly, though, if the chain tangles or binds. Any force at this point can damage the chain, the chainrings or the derailleur. If you have enough momentum, you can backpedal to free the chain and then try shifting it again.
Set the chain back on. If nothing works, click out and stop before you teeter over. You’ll have to re-rail the chain by hand. When it has fallen to the inside, sometimes you can do it by picking up the rear of the bike so that the chain drapes over the small ring. Then turn the crank by hand so it catches the teeth. Otherwise, look for a stick or piece of litter so you can pull the chain up and on without soiling your hands. Another trick is to use one of the tire levers you should be carrying in your seat bag. Or the spare rag you might have wrapped something in.
Use a Chain Catcher. There are several commercially available chain catchers. They work by physically preventing the chain from falling off inside the small chain ring. In effect, they “redirect” the chain back onto the small ring.
My wife threw her chain from the small chain ring into the space between the crank and the frame . It ended up so wedged, there was nothing I could do out in the field , because the entire crank would not rotate . I ended up removing the entire crank with chainrings on a repair stand at home , because even the pliers on the multitool I had carried with me would not remove the wedged chain from the gap .
Your wife and I work from the same bag of tricks. I had a chain catcher and I would occasionally jam the chain between the catcher and the frame. It was impossible to dislodge without a workstand and tools I took the chain catcher off.
I find it easier to carry a pair of thin gloves (they weigh nothing and take up no space). With gloves, replacing the chain on the chain rings is much easier and much cleaner (on the hands).
Also, when trying to replace the chain on the chain rings, the chain is often tight. Just push the rear derailleur pulley assembly forward…this will usually free up a lot of chain and allow replacing it on the chain rings much easier.
My motto in this issue is “Never touch the chain.” Shifting off the big ring is rarely not addressed by simply shifting it back, but when it drops off the small ring shifting back doesn’t always work. When this happens, I lean the bike toward the crankset side while standing on the other side. Using the toe of my shoe, I push the chain onto the small chainring and then reach over and rotate the cranks to get the chain fully engaged. I haven’t had to put my hands on a chain in decades.
If the chain gets wedged, one thing that helps is to pull the rear derailleur forward, that gives you some slack to work with and gently pulling the chain from the bottom, work your way up to the top. If you start at the top, it just wedges the chain deeper on the bottom.
Sometimes the chain falls off and if I can’t find a stick to hold and move the chain back onto the chain ring, I have to touch the chain.
So that finger has to get wiped off after this, and that is why I always wear black cycling shorts and socks.
That’s how I met my wife. I was the one who stopped to help her reacquire her thrown chain which occurred at the start of a steep hill. Many miles since….
My E-bike (Specialized Creo) has a rear deraileur with a CLUTCH. It is supposed to make getting the rear wheel off easier.
If you accidentally disengage the clutch, the chain will come off at the worst times.
Learn the correct position of that little lever, and make sure you don’t accidentsally throw it into the wrong position when changing a tire… in the rain… don’t ask.
I have a K-edge chain keeper on every bike that will accept them. I like the pro models that mount to the FD and are adjustable without affecting the FD position.
The VERY first thing to do if you throw a chain is STOP PEDALING. If the chain is too jammed up to move with a soft pedal it best to safely stop the bike to fix. If you can move the chain with a soft pedal, then try shifting that FD while (as the article says) GENTLY continuing to pedal. A rider trying to ‘horse’ the chain back on with a brute force pedal stroke risks jamming the chain hard against the bottom bracket- and/or damaging (even breaking) the chain.
I am presently using a 44/32/22 on my road bike and have no problems. I bought a used Suntour MicroDrive crankset with 42/32/20 combination. When the mechanic installed and checked it on the bikestand, the chain would fall off when shifting from the 32 to the 42 chainring. What is wrong?