Yep, it’s a fact of life for anyone riding a bike with multiple chainrings.
You likely know how it happens. Slowing down, or approaching an incline, you perform a front shift in anticipation. Instead of the chain smoothly moving onto the small chainring, it overshoots and falls off, getting trapped between your smallest chainring and your seat tube, as it rests on your frame’s bottom bracket shell.
Remedying it when it does happen while riding is easier than you might think, and you can do it without even stopping. Remember that chain drop happens upon shifting to your smallest chainring, so to fix it, do the opposite. With momentum, shift to a larger chainring while pedaling lightly. With luck, the chainring teeth should catch the chain as the front derailleur pushes it outward, back onto the big chainring and returning drive to your legs.
Of course, preventing chain drop in the first place would be best. Unfortunately, no matter how well you tune your front derailleur or how tightly you set its limits, chain drop can still occur. The next best thing you can do is to get some extra insurance.
That’s where this itty-bitty piece of cleverly shaped metal comes in. It’s called a chain catcher.
This little aluminum arm basically “catches” the chain when it overshoots a shift to the small ring, instead of letting it drop onto the bottom bracket shell. The bottom of the chain catcher has a ramp section which guides the chain back onto the small chainring as it falls.
The clever bit for me is how it’s mounted. Most road bikes already have a braze-on-style mounting plate on the seat tube, where a front derailleur bolts on directly to its rear. The chain catcher has basically the same fitment method, only over the front. It’s an elegant use of space.
Token’s chain catcher kit is pretty simple. All it contains is
- the chain catcher itself, anodized red
- a spare shaped washer for the front derailleur
- some cylindrical spacers, and
- a pair of longer mounting bolts.
This is meant to replace the bolt that came with the front derailleur, because that will be too short to mount the chain catcher. I’m told the anodized red bolt is structurally weaker, so I used the normal silver one.
Mounting it is straightforward. It would help greatly if you’re familiar with tuning a front derailleur, since installing the chain catcher basically requires dismounting the front derailleur first, and setting its proper position is part of tuning anyway. That aside, it’s just a matter of swapping bolts, threading the chain catcher on, adding any necessary spacers, properly setting the chain catcher’s angle, and torquing the whole caboodle down to spec. You want the chain catcher angled inward enough to do its job, but far enough away to prevent fouling the small chainring or crank arm spider as they spin.
That’s it, really. It’s going to be a pain if your road bike frame uses a band-on type of front derailleur, but for everybody else, a chain catcher is very cheap insurance.
the accidental randonneur 