The major difference between electric bikes is the various types of drive systems they use. These include shaft drives, mid-drives, geared and gearless hubs. In addition, there are differences between the motors, chiefly brushed and brushless. Therefore, if you are looking for an e-bike for a specific use, this article will help you to understand and focus on finding the right one.
The shaft drive
This system works more like the arrangement in an automobile, with the motor positioned more towards the center of the bike and driving the rear wheel with a shaft. These are not popular nowadays, because of the customized frames required to support the motor and shaft. The entire arrangement is awkward and difficult to service.
A mid-drive motor
Mid-drive motor systems are used in e-bikes meant for climbing. You will find this design close to the bottom bracket, at the point near the pedals. The system drives the chain forward rather than the wheel, benefitting from mechanical drivetrain systems such as use of gears for going fast or for climbing. Therefore, when approaching a hill, the rider can shift to a lower gear, making it easier to pedal and climb.
The geared hub motor
There are two types of hub motors – geared and gearless. The geared hub motor provides mechanical advantage with smaller and lightweight motors. However, they also produce more friction and hence more noise and wear out faster. A built-in flywheel mechanism unlatches the shaft from the axle while the rider is coasting, preventing addition of any resistance.
The gearless hub motor
The simplicity of the gearless hub motor delivers smooth and quiet performance, much eulogized by shops selling e-bikes. These motors rely greatly on electromagnets and most do not even include a freewheel mechanism. That may be due to the extremely low magnetic resistance to be overcome when the electromagnets are powered off. Usually, such motors are also called direct drive systems, enabling regeneration of electricity from repelling magnets within the motor.
Gearless hub motors are generally larger than other types, because they need to accommodate magnets, ultimately making them weigh more. However, improvements in technology are helping to produce small and lightweight direct drive hub motors nowadays.
Hub motors usually operate even when the rider is not pedaling. Whether geared or gearless, the system can fit in the rear or the front wheel. However, with increased unsprung weight, hub motors can experience reduced traction, limited efficiency and strain the spokes and rims of the wheel.
The drive system you select will affect the overall weight and weight-distribution of your electric bike. The cost will depend on whether you need a customized frame, regeneration and special sensors for shifting gears. Motorized e-bikes provide improved efficiency, help in riding fast, in climbing and in navigating bumps. For lightweight around-the-town transportation, geared hub motors are fine. If you like quieter rides with more power and regenerative braking, go for direct drive hub motors. However, if you ride your bike more in the mountains and do lots of hill climbing, you definitely need mid drive motors.