Swiss manufacturer Schlumpf Innovations produces two-speed, planetary gear-driven crank/bottom bracket systems. With a Schlumpf Speed Drive, Mountain Drive, or High Speed Drive, you can expand the gear range of a single-speed, fixed-gear, or internal gear hub-equipped bike while maintaining a clean look.
With Schlumpf's gearing systems, two gear ratios are available without the chain moving between gears, and there's no front derailleur, shifter, or cables to maintain or clutter up your bike. You simply shift with a quick heel movement against the push-button axle in the center of the crank arm. The gearing systems use a clutch plate design that won't slip under power and they require very little maintenance.
Cycle Monkey offers all three of Schlumpf's gearings systems: Speed Drive (1.65 overdrive ratio), Mountain Drive (2.5 reduction ratio), and High Speed Drive (2.5 overdrive ratio) in all the various configurations. We also have a longer axle version that is compatible with the 54mm chainline of the Rohloff SPEEDHUB 500/14. Crank arms are available in black or silver in a variety of lengths.