The Paul Chain Keeper is a chain retention device for 1X single ring drivetrains. It’s available in models to either clamp on a seat tube in place of a derailleur (shown here), or mount on an external bottom bracket. The seat tube version is available in three sizes to fit 28.6mm, 31.8mm, and 35.0mm seat tubes. The external bottom bracket model is intended for full suspension frames, carbon fiber frames, frames with eccentric bottom brackets, and frames with non-standard tubing.
Not all 1X set-ups require a chain keeper. If you’re doing a conversion, my advice is to give it a try sans keeper for a week or two to see if chain derailment is going to be an issue. Drivetrains set-up with good alignment and high tension may never throw a chain, particularly if the shifters are indexed and the bike is only used on relatively smooth, paved roads. But, if you plan on riding your bike on dirt trails, or if you’re an aggressive rider who hops curbs and so forth, a chain keeper of some sort is definitely in order. I decided to install the Paul Chain Keeper on my bike because I occasionally ride dirt trails, and I sometimes hop curbs when transitioning from bike lanes to off-street paths.
The Paul Chain Keeper works as advertised; with this unit installed, your chain will not derail, period. The fit and finish are excellent, and like all Paul components, the Chain Keeper is manufactured right here in Chico, CA, USA.
I purchased my Paul Chain Keeper at The Bicycle Business in Sacramento, CA (thanks, guys!). They can also be ordered directly from Paul in Chico.
Note: The Bicycle Business is a sponsor of this website.