Schlumpf (swiss) mountain drive is a planetary 2 speed crankset in low range its reduced by 2,5Times ..
crankarms turn faster than the chainring..
so for example a 50t when you kick the shift button thru it, acts like a 20 t ..
you can put a 34t chain ring on the 110 spider version , its like a 13.4t in low. or a 38t on the 130 version for a 15.2 t equivalent
Mine is on my Brompton M3L a 130 type with a 54t (21.6t low) 15t cog... the AW hub's 3 speeds are used twice.. low in the 17" range.
almost 1:1 with the 16" wheel .
Last edited by fietsbob; 08-08-14 at 09:43 PM.