a rear - wheel drive for a bicycle or a trailer bike comprises an output sprocket of a chain drive , a rear - wheel shaft , and a driving mechanism being supported outside to the bicycle frame . the rear - wheel shaft is supported only on one side of the driving in a supporting manner relative to the bicycle frame . the driving mechanism on the side facing the bicycle frame is not , as commonly known , supported relative to the rear wheel shaft but relative to the bicycle frame . that creates the required space for arranging a freewheel clutch , that fulfills the strength requirements for transmitting the occurring torques even when using sprockets with only a few teeth . thus , short distances between the rear wheel and the bottom bracket and single - arm suspensions in the bicycle frame can be implemented together with the implementation of suitable developments of the chain drive for small running wheels .