What Is a Hub-drive Motor?

For a hub-drive, the motor sits on the front or rear wheel inside the wheel hub. The motor provides driving force by spinning the wheel on which it is mounted. When placed on the front wheel, it will feel a bit like the bike is being pulled. If on the rear wheel, it feels very similar to normal pedaling. For this reason, a well-designed rear hub-drive solution is a really good solution from a technical point of view.

Bike component manufacturers supplying to e-bike manufacturers seem to prefer mid-drive motors as there are fewer bike-specific parts available for hub-drives (spokes, rims, tires, color options, etc.).

Hub motors come in two main types: geared and direct drive. Geared hub motors have internal gears that reduce the motor’s RPMs, but increase the torque output, making them better suited for hills and steep terrain. Direct-drive hub motors do not have gears, and produce more power but are heavier and less efficient at low speeds.

Hub motors have several advantages over mid-drive motors. They are generally simpler and require less maintenance, and do not interfere with the bike’s existing drivetrain, making them easier to install and use. The main advantage however is that only human power needs to go through the chain/belt. With a mid-drive, both the motor power and the human power needs to go through the chain/belt. This increases wear and requires a more beefy chain.

One disadvantage of hub motors is that they can add weight to the wheel, which also needs to be spun up when accelerating (rotating weight). This can slow down acceleration. Front hub motors are really easy to retrofit on an existing bike, but they are generally not recommended as the bike handling is often quite unpredictable (which is really bad for safety).

There are e-bikes with hub-drive on both wheels, which may be a bit strange and can be compared to 4-wheel drive on a car. Done right it can work well, but this is an uncommon configuration.