Originally Posted by harrier
The bike has an internal hub, so I don't know why it needs a vertical dropout hangar with a chain tensioner anyway.
Chains elongate as they wear, and every bike need a way of keeping the chain reasonably tight.
On bikes with only one rear sprocket this is usually accomplished with (semi-) horizontal dropouts, forwards-facing for most(utility-oriented) bikes and backwards facing for track(and other performance oriented) bikes. As the chain stretches the wheel is moved backwards until a whole link can be removed and the process starts over.
If you are running vertical dropouts you need to add some other feature if you want to avoid having the chain thrown at every 2nd bumb you pass.
- assymmetric bb
- assymmetric hub axles (not compatible with internal gears I believe)
- half links
- ghost sprockets
....or a chain tensioner....