I have a Tern Vektron with a Nexus 7 hub.
In general it has been great bike, but I have had chain tensioner trouble twice. The first time was not long after I bought the bike. I was going down a slight incline, transitioning from freewheeling to pedalling as the slope levelled out, went over a bump, and the chain got caught up with the chain tensioner being pulled back and up. I was able to ride it after repositioning, but it happened again soon after. There was no clear indication of why this had occurred. Alignment etc was checked, tension seemed ok, but the problem occurred again soon afterwards. The chain tensioner was replaced with the same Shimano model and all was good for several thousand km.
A few days ago, it happened again. Exactly the same cicumstances - downhill, over a bump just as I was beginning to pedal after freewheeling. I was able to ride it home. I can see that the tension is not what it should be - my impression is that once the tensioner is pulled up and back like that, even if one stops pedalling immediately (not that there is much option), something alters and the tensioner will not exert the proper tension again. It feels like a chain with one too many links in it.
Has anyone experienced this?
I am thinking about abandoning the Shimano tensioner and trying a Surly Singulator.
I’m not sure if it is relevant or not, but it has always been impossible to backpedal with this hub - while it doesn’t push the chain forward when freewheeling, and indeed doesn’t seem to have too much drag when freewheeling, there has always been a lot of resistance when turning the pedals backwards, to the extent that I have always avoided doing it on this bike unless I’m fettling it.
Any thoughts? To be frank I’ve always thought that needing a chain tensioner negates some of the simplicity of having a hub gear and kind of wish I’d got a derailleur version. (Edited to add: because then I’d be on familiar territory).