Schlumpf Drive

A Schlumpf Drive is a two-speed planetary gear assembly for use on bicycles and unicycles.

It is distinct from other bicycle planetary gear assemblies in that it is located behind the chainring rather than in the rear hub.

A push-button on each side of the axle allows the rider to switch between high and low ratios.

Shortly afterward, a collaboration with Kris Holm led to a co-branded mountain unicycle version that bore higher loads and no longer required an external torque lever.

[4] Since 2012, the entire range has been manufactured in Germany by Haberstock Mobility, following an agreed buy-out in late 2011.