Ask a Mechanic: Setting up a Chain Catcher

I’m confident that my front derailleur is set up properly but I still dropped my chain a few weeks ago on a rough road. Should I be using a chain catcher?

Installing a chain catcher on your bike is one of the cheapest and easiest ways to eliminate chains dropped between the small chainring and the frame. Over the years I’ve seen plenty of bikes bearing the scars of a dropped chain, which can actually damage the integrity of carbon frames around the bottom bracket area—never a good thing. The consequences aren’t as high with an alloy frame, but nonetheless, a chain watcher will keep the frame damage-free and looking good.

All chain watchers are easy to install, as most of them are fastened with one bolt. Sram has even gone as far as integrating a chain watcher, which they call the Chain Spotter, into their front derailleur bolt, making for a very clean and effective set up. With the Sram Chain Spotter all you have to do is replace the derailleur bolt with the integrated version of the bolt, and then add the Chain Spotter, which sits over the outside of the bolt. The only thing to watch is that the tab on the curved spacer is oriented down to allow for adjustment of the Chain Spotter. You’ll have to re-adjust the front derailleur after replacing the bolt, which we’ve covered in other videos. Once adjusted, shift the bike into the small chainring and largest cog in the rear. Now we can place the chain spotter over the bolt and attach it with the additional bolt provided. I like to barely snug up the bolt using a 2.5 mm allen wrench, and then use the same wrench to adjust the distance of the chain watcher in relation to the chain. Use the same 2.5mm allen to move the chain spotter as close to the chain as possible without rubbing. Once the chain spotter is where you want it, tighten it down securely so it doesn’t rattle loose and fall off.

Although the Sram Chain Spotter can be used with non-Sram derailleurs, there are other options as well such as the K-Edge Pro Braze-On Chain Catcher. The set up process for these chain watchers is very similar to the Sram Chain Spotter. Just replace your current front derailleur bolt and spacer with those provided in the K-Edge kit, then adjust the front derailleur as you normally would. Once the derailleur is set, put the chain catcher over the bolt and then use the secondary bolt to hold the catcher in place. Again, I like to just snug the bolt up, then set the distance between the catcher and the chain, then tighten it down securely.

If your bike doesn’t have a braze-on style front derailleur mount, I recommend using the Sram braze on clamp adaptor and Sram Chain Spotter. The braze-on adaptor has the support tab built in to it and offers a clean set up when done.

If installed properly, your chain catcher will make dropped chains a thing of the past, providing extra security when shifting the chain to the small ring. It’s worth the relatively low time and cost to save your frame from damage, and will likely save a ride without you ever even knowing.