Originally Posted by
chagzuki
Doh! Hadn't even gotten as far as thinking that'd be swappable. It's whatever comes with the gear hub, I assume. Though looking at it I can't see the hub could fit anything smaller.
Try to swap out the rear sprocket first and see what that gives you. Most of the time its easy and surely cheaper that the front ring. Some Shimano rear sprockets are as simply as removing the wheel and clicking out with a screwdriver. Not sure about that SA one, though.
If you had kept the front fender, the BB area would not look so dirty. That's been my experience anyway.