Fundamentally, the working principle of a wheel hub motor is similar to that of a mid-drive motor- they both provide assistance that boosts your pedal power, enabling you to accelerate faster and ride with less effort. The difference is in the way the wheel hub motor obtains and applies its assistance.
Rear hub motor
On rear hub electric bikes, the motor (you guessed it) is located inside the rear wheel. This means that it is very close to the mechanism that moves the bike forward. When you pedal and the chain pushes against the flywheel, the rear hub motor measures the force on the rear wheel. Once it calculates how much power you’re inputting, it applies its own force directly to the rear wheel, pushing the wheel (and the entire bike) forward. Some wheel hub motors, such as those on most electric road bikes, are able to measure power multiple times during each pedal stroke, making them highly responsive. Others are simpler and only measure a few times per stroke, but are usually less expensive and can be seen on some hybrid or city electric bikes.
Front hub motor
Motors located in the front wheel are generally considered simpler than rear hub motors because they are not directly connected to the bike's “driving” mechanisms. This means that they don’t provide assistance to the drive wheel. Instead, the front hub motor is induced as the rear wheel is propelled forward. Because it is directly connected to the front wheel, the motor then applies its assistance to that wheel, which means that as you continue to pedal and apply power to the rear wheel, you are effectively being“pulled" along.
Like other electric bike motors, some front wheel motors have a sensor that calculates how much assistance to provide when it senses a certain amount of drive force. Other, typically less expensive models, may provide a fixed amount of assistance no matter how hard you pedal.
By 2028, the global wheel hub motor market size is expected to reach $12.5 billion. Additionally, it is predicted that this market will grow at a compound annual growth rate of over 5.0% from 2020-2028. The key drivers pushing consumer demand for wheel hub motors are increased vehicle efficiency and growing acceptance of electric bikes. Additionally, the rise in electric vehicles and heavy investment in upgrading engine technology have contributed to the industry’s large share of the market. Government initiatives to limit fossil fuel consumption have caused electric vehicle manufacturers to invest more in upgrading technology, thus driving demand for wheel hub motors.