Blackspire Stinger E-Chain Tensioner
The most affordable Dual-Ring chain tensioner in the world! For use with Shimano FD-M970-E/FD-M770-E E-type front derailleurs.
I'll be brief with this review because there's not too much to this thing. Do I like it? Yes. It does exactly what it says it will, it does it without complaint or much fuss. It's durable, it doesn't weigh much, and it's inexpensive. I unfortunately gave it to a friend after I bought a triple-ring crank for XC racing, but now that I'm done with that, I'll be buying another one. I also have the non e-type version of this on my bigger-hit bike and it works just as well. Setting this thing up is easy. Take off the cranks, take off the BB, slip this on in place of a spacer, put the BB on loosely, get the angle you want, and put on the cranks. You'll likely need to mess with the spacing of the pulley to get it to shift onto the roller step, but it's all pretty easy stuff. No manual, but it really doesn't need one! (you can get one on Blackspire's website if you need it!) Getting the derailleur set in right is a bit tricky, but that's nothing new for front derailleurs. Those are always troublesome! There's really no other product like this on the market, and it meets a very specific niche, but it does so extremely well, and for not much money! So, if you need a dual-ring guide for a bike that uses an e-type front derailleur...this is the thing you need!