An Electric Bike for You? Part 2

Roger Fife

As a follow up to last month’s article on e-bikes, this installment discusses two important, relevant topics: classes of e-bikes and power sensing. The final installment, planned for next month, will be advice on purchasing an electric bike.

There are three e-bike classes. Some of the following definitions may vary by trail or state.

Class One e-bikes are pedal-assist only with no throttle and a maximum assisted speed of 20 mph. They are legal on any paved surface and off-road trail that a regular bike is allowed to operate.

Class Two e-bikes are also pedal-assist and have a maximum speed of 20 mph, but possess throttle-assist. These e-bikes are legal on any paved surface that a regular bike is allowed to operate.

Class Three e-bikes are pedal-assist only with a maximum assisted speed of 28 mph. Class three e-bikes are prohibited from multi-use bike paths and off-road trails unless specifically authorized.

In addition, all classes limit motor power to one horsepower (750W).

Power-assist is either “cadence sensing,” which considers if you are pedaling, or “torque sensing,” which considers how hard you are pedaling.

Cadence Sensing (Basic)

Manufacturers that produce inexpensive e-bikes use cadence sensing technology, because the sensor itself is less expensive, but the disadvantages are that the pedal assistance can feel jerky, delayed, and counterintuitive. The basic cadence sensor uses a magnet on the crank to turn the motor on when you start pedaling and turns it off when you stop pedaling.

Torque Sensing (Advanced)

Torque sensing is a totally different technology that uses a precision strain gauge that measures your actual force on the pedal (sampling it perhaps 500 to 1,000 times per second over the entire pedal stroke). It makes this adjustment in real time, so it is technically amplifying your input. It feels like you are bionic.

Another huge advantage of a torque sensing e-bike is that you get a significant amount of range increase, sometimes as much as double.

If you have a chance to ride a cadence sensing e-bike and a torque sensing e-bike back-to-back, you will notice the difference. The torque sensor setup makes the bike feel like a normal bike, but with more power. You also feel more in control of the bike.

Levels of power-assist on most torque sensing e-bikes are level 1 – 25% assistance, level 2 – 50% assistance, and level 3 – 75% assistance.

The levels of assist are selected on the operation control unit on the handle bars. In addition to the motor assist levels, the rider can select gears, of which there are typically nine. With this combination, you can go anywhere and climb almost any hill you encounter with minimal exertion, but you always will get some exercise.