As if a whole new Saint groupset wasn’t enough, Shimano have now let the cat out of the bag on a prototype chain device.

As you can see from the photo below this looks like one highly polished prototype, but we wouldn’t really expect anything less from Shimano. Despite looking like a finished article the word from Shimano is that this is still very much an early prototype and they’ll be using their sponsored riders for testing and feedback over the following year, so don’t expect to see it in the shops any time soon.

So what can we make of it then? Well the most obvious feature is the segmented bash ring (if you can still call it a ring?). The thinking behind this is that most riders have a leading foot and so if you’re going into a section where you’re possibly going to grind out you only need to protect one side of the chainring. It’s not the first time this has been done, but I am still not sure it works so well in reality. I thought I always led with the same foot, but if I look at my bash ring it has dents and scrapes all over it. Shimano say that you could always run two of these segments to protect both sides, but then surely you might as well just use a full bash ring? If you run one though then the setup is very competitive in the weight stakes at a claimed 147g for the whole shebang.

Another point worth noting is the lack of a lower roller. Instead Shimano have gone down the Straitline and Gamut route of using a simple slider instead. They reckon the friction from this is at least on a par with a roller, if not better, particularly when at the extreme ends of the cassette. Apparently it’s all to do with the amount the chain has to be bent around the lower guide, and with this system it’s less than a roller, and therefore more efficient. The other interesting thing with the lower guide is that it’s fixed to the backplate via a sprung loaded pivot. This is so that it can move out the way if hit by a rock, but for now at least I can’t exactly work out how that’s going to work because the guide is already close to the chainring and so there’s very little room for it to move (considering that it pivots around the bit that you can see).

Obviously this is still a prototype and could be subject to serious change, but as it stands I am not sure how well this device will work, even when ignoring the potential for impact damage caused by not having a full bash ring (or backplate mounted Taco). My main concern is with the the way both the upper and lower guide have to be very ‘open’ in order to allow the segment of bash ring to clear as it rotates. To me it just looks like there’s a whole load of room for the chain to escape from. Maybe Shimano feel that full enclosure of the chain isn’t so necessary when you’re using a Shadow+ rear mech, or maybe it’s just not as open as it looks?

Anyway, enough speculation from me, what do you lot reckon?