(Original Post 07.07.17)

So following on the installation of the 24T chainring, I did actually order one of those N-Gear Jump Stop chain guide thingys. There were no surprises or difficulties on installation, and I look forward to being able to dump the chain down onto that ring even under a bit of pressure without having to hop off the bike a couple of seconds later. N-Gear Guy has put a good bit of thought into it and as an inveterate tinkerer with things of course I’m gonna order the product from the little guy. Especially if it’s cheap.

For MTBs there seem to be versions that attach to the front derailleur clamp, but this situation of a huge drop down to the granny gear seems to be a more touring/randonneur-specific thing and I’m not sure how brilliant an idea it is to have something reaching down that far from its single attachment bolt, which gives the chain, hitting it, a lot of leverage. This one clamps the guide in a way that makes it well able to resist the force of the chain, and you can adjust it so that the chain doesn’t really have much of a chance to go anywhere.

A package with a cardboard label at top saying "Jump Stop chain guide" and a clear plastic bag, where the product is mostly obscured by a paper leaflet inside the bag. Something metal is visible below the leaflet.
Jump Stop in its package
A hand holing a thing consisting of a black plastic ring attached to a shiny metal angle. Both held together by an Allen bolt.
Jump Stop
Bottom bracket and chainrings area of a bike seen from the non-drive side showing the Jump Stop installed below the front derailleur so that its plate is parallel to the (very) small chainring where it can prevent the chain falling down on the inside.
Fitted

Update on 19 July 2017: Seems to work as expected! Changing down onto the small ring no problem!

Longer-term update 2022: After a fair bit of use, it’s still fine. Like everything on the bike, the adjustment should be checked from time to time, though I think what happened the one time I dropped the chain was when I’d slapped in the new bottom bracket without bothering to reset either the Jump Stop or the front derailleur … my bad. Note: an X-mm BB from manufacturer A will not necessarily give you exactly the same chainline as a X-mm BB from another manufacturer.

I was clever enough to order 2 of these at the time, and no. 2 is now on New Old Bike …