Geared hubs and direct drive

A geared hub uses planetary gears so a small, fast motor can turn a wheel. It is lighter, it freewheels when you pedal without assist, and it is the usual city and hybrid conversion. Grin’s GMAC is the geared hub builders specify when they want the controller documented. Bafang’s 250 W rear wheels are the geared pattern most European street kits follow.

A direct-drive hub is a larger magnet ring. It takes abuse, it can be run hard, and some controllers let it regenerate on descents. It is heavier, and you can feel it when the motor is off. Cargo wheels and high-power builds tend to land here. The drag is the trade for the simplicity.

• Geared: lighter, quieter at speed, a clutch or freewheel to service, less happy as a huge continuous load.
• Direct drive: heavier, smoother under big current, possible regen, a slight drag.
• Neither number tells you the axle or the brake. Read those next.
• Noise in a geared hub after a wet winter is a service question, not a reason to open it on the pavement.