When the first electric bikes hit the market, they came equipped with wheel hub motors. This was a revolutionary feature for commuters. Wheel hub motors, also known as direct-drive motors, are electric motors that are placed either on the front or rear wheel, directly powering that particular wheel. With this assistance, less energy is expended when riding compared to regular bikes.
Mid-drive motors change the way electric bikes function. Rather than providing power to one or both of the bike’s wheels, the mid-drive electric system powers the bike’s gears. This difference has some effects on the electric bike. It’s mainly used as a more efficient power delivery system. Instead of assisting the bike’s movement by providing power to the wheels, it instead helps the rider pedal (known as pedal-assist).
Mid-drive motors are also known as central hub or center motors. They are mounted on the bike’s pedal, making them perfect to power the bike’s transmission system (including the pedals, chain, flywheel/freewheel, and derailleur). Mid-drive motors also usually provide better weight distribution as they are located in the middle of the electric bike.
Mid-drive motors are placed on your electric bike’s pedals, while wheel hub motors are placed on one of your bike’s wheels. It may be the front or rear wheel. This placement affects something called weight distribution, making the bike more or less maneuverable. In my experience, mid-drive motors improve the maneuverability of electric bikes due to their location. For all vehicles, the closer to the center of gravity, any added weight becomes less noticeable.
Wheel hub motors directly power one of the bike’s wheels. Therefore, for example, a rear hub motor is placed on the rear wheel. On the other hand, mid-drive motors work in conjunction with your bike’s gears. This makes the mid-drive motor more efficient than the wheel hub motor. However, you do need to pedal with the mid-drive motor, whereas with a wheel hub motor (including pedal-assist), you can take a short break and let the motor power the electric bike until it decelerates.
Due to the fact that mid-drive motors work in conjunction with your gears, they are generally more efficient than wheel hub motors. When you shift to a lower gear, the motor doesn’t have to provide as much power because it’s easier to keep up with a naturally pedaling rhythm. Likewise, when you shift into a higher gear, the motor has to do more work, but the changes aren’t as noticeable (the pedal-assist continues to work smoothly and the pedal speed doesn’t shift abruptly). Therefore, when in higher gear, you will get a greater range from a mid-drive electric bike motor because its workload isn’t constant.