There are two main types of hub motors currently on the market: geared and gearless also called “direct drive or brushless” hub motors.

Gearless (Direct Drive, Brushless) Bicycle Hub Motor

With this type of drive, the motor’s axle is the same axle that goes across the center of the motor. There are copper windings attached to the axle. If you combine all these components, they are together called a “stator.” Magnets are placed on the outer portion of the motor, and these create a magnetic field when electricity is introduced into the stator. The ensuing movement of the magnets is what causes the motor to move the bike.

Direct drive hub motors can provide large amounts of torque and power. This makes them especially well-suited for higher performance electric bikes. Direct drive motors are usually big and heavy which adds to overall bike weight and decreases range. On the upside, this extra mass helps the motor to keep from overheating as easily because the thermal mass of the motor functions as a heat sink.

Recommended for heavier loads, max performance, top speed.

Geared hub motors

Geared hub motors have their cases connected to the stator through a planetary gear reduction system. For every rotation of the case, the motor inside turns faster. This allows the motor to work at higher and more efficient speeds, while still allowing the wheel to spin at slower driving speed.
Geared hub motors are smaller and lighter than direct drive motors, which can help with increasing range, but they are also less powerful and can wear out more quickly.

Most geared hub motors are only rated up to 500 watts of power, though the larger BPM geared hub motor has a rating up to 500 watts and has been successfully used on ebikes up to 1,000 watts, though with a shorter life expectancy (of the motor that is, not the rider).

Recommended for everyday commuter, light weight, long range.

Comparing Direct Drive and Geared hub motors.

Choosing between a geared or direct drive hub motor usually comes down to two considerations: your power and weight requirements.
If you are predicting your electric bicycle with a lightweight setup in mind, you are pretty much limited to a geared hub motor. If you are looking for a powerful ebike, especially an ebike over 750 watts, your best option is the direct drive hub motor.

If you are looking for converting your existing bicycle gearless motor is a better choice. You get more power for the buck, no maintenance and great speed. If you are looking for an ebike you’ll more likely get a geared motor. Its smaller, lighter and has great torque for up hill ride.