Electric Bike Motors: Various Motor Types
Direct Drive Motors
Because the motor attaches directly to the wheel that it powers, hub motors are more efficient. These are completely sealed and less exposed to the elements, making them more durable in wet and gritty environments. Hub motors can be easily swapped in and out if there are any mechanical issues. Crank motors are placed in or near the bottom bracket of the bike creating a lower center of gravity and contributing to a better balanced bike. Geared hub motors work with the gears of the bike and as such can produce greater torque, meaning that they produce more drive and will inevitably perform better while going up hills.
Because they are sealed, overheating can be an issue on long rides. We suggest that if you will often be riding your electric bike on long trips not to go for a hub motor. Over time, the excessive heat will reduce the lifespan of your motor significantly. These motors use the entire hub shell as the motor and add significant weight to the back wheel. As they are sealed, it is difficult to tell the difference between a good and bad hub motor. Most crank drive motors are proprietary meaning that they are specific to each manufacturer so if you need to replace any parts you cannot buy knock off or off-the-shelf parts and will often need to buy manufacturer specific parts.
Front or Rear Hub
Front hub motors provide power directly to the front wheel and the riders’ pedaling propels the back wheel, giving an “all-wheel drive” sensation. This style are easier to install, maintain and repair as you don’t need to work around gears, chains and cassettes.
Rear hub motors have have considerably stronger frames to handle higher power options from the extra torque to the rear wheel from the motor. These hubs make riding feel more natural to riders who are more used to traditional bicycles. Rear hubs can provide throttle, cadence and/or torque sensor pedal assist where as front hubs cannot offer torque pedal assist. Rear hubs can be more difficult to install as they need to be worked around the drivetrain.
Are fitted in the middle of the bike wheel and don't changing the basic design of the bike. They are usually fully contained in the motor’s shell within the hub. This style of motor are attached directly to the wheel that they are powering and the spokes are threaded from the motor to the rim.
A geared hub motor of equal power to a direct drive hub motor will tend to be smaller and lighter. These have greater torque but cannot reach speeds as high as Direct Drive hub motors due to a maximum speed that a gear can turn at. There can be a hum associated with geared hub motors because of their engaged moving parts.
Geared hub motors are generally more about smooth and efficient performance than brute force. Unlike direct drive hubs, geared hub motors often have a fanned casing, in order to prevent overheating and remove that as a variable that will impact lifespan. The rule of thumb with hub motors is that you “pay less and get more”.
The whole motor unit is completely sealed. The amount of power a geared hub motor can exert is limited by the strength of the chain and gearing sprockets. Ordinary bike chains and sprockets are not made to be strong enough to withstand motorized use.
Read more in our electric bike motors tutorial.