A couple of points of interest regarding the Alton's...........On the twins I've noticed that the new plastic drive sprocket that comes in the kit has teeth much wider that the stock steel item. this gives very little in the way of movement of the chainwheel, which can move quite a bit if the bushes are worn, and they do move a lot in service. I'm pretty sure this would contribute to the plastic shedding off the teeth. The other point that one of our members way up north had, was after either washing the bike and/or in heavy rain, with the bike resting on it's side stand, the Alton filled with water which had no where to drain successfully from, and this did serious damage to the internals. I am not sure if anyone else has had this problem, I haven't bothered to check if they have drain holes around the base of the unit, but I will next time.