Originally Posted by
fietsbob
cranks on newer BMX bikes fit a 9t on the back wheel,, chainring is something like a 32t on those cranks..
It's smaller than that, I've run across BMX chainrings with 20 teeth!
Originally Posted by
Dan Burkhart
I'm using a 30 tooth chainring and a 25 tooth cog on mine with 700 32c. Low gear is about 32.5". I did experience a 4th gear failure resulting from a chipped pawl due to a shift cable not running freely.
I thoroughly cleaned and relubed it, and it's buzzing along just like new.
I think you could probably go even lower on the input ratio as long as you stick with low gear for hard climbing as the torque is transmitted directly from stage to stage via the pawls engaging the ring gears and no power is transmitted through the gear train in low.
https://www.youtube.com/watch?v=kJIh64i9IAY
That video is awesome! I knew roughly how the hub worked before, but not the specifics. Now I'm a) set to poke around inside it if I ever have to and b) able to explain exactly how it works to fellow bike geeks.