To enable the electric bike's motor to know when to start or stop, signals must be received through a controller, which needs to detect whether the rider is pedaling. For this reason, all electric bikes are equipped with one of two types of sensors: cadence sensors or torque sensors.
Until recently, cadence sensors were largely found on lower-priced electric bikes, while torque sensors were exclusive to high-end models. However, as the cost of torque sensors has decreased, some electric bikes priced under $2000 now come with torque sensors, making this specification a key factor to consider when choosing an electric bike.
The two types of sensors operate on fundamentally different principles and determine how the motor provides power, leading to varying riding experiences. Neither sensor is inherently superior; riders often develop a preference for one over the other.
Differences Between Torque Sensors and Cadence Sensors
Both sensor types work by detecting pedal movement, or more precisely, the movement of the crankshaft. Let’s first examine cadence sensors, which operate on relatively straightforward principles.
Cadence sensors are typically installed at the bottom bracket of the electric bike, featuring a ring of sensors (usually 12). A magnet is mounted on one of the crank arms, and as it rotates, the magnet passes by the sensors. Each time it does, a signal is sent to the controller to activate or maintain motor power. The operation of cadence sensors is binary: are the pedals turning or not? The pedals must rotate at a steady speed for the motor to remain active; however, the speed of rotation is not particularly important. Moreover, requirements for cadence sensors vary, but most require the pedals to rotate at least a quarter turn to activate the motor.
Torque sensors, on the other hand, work completely differently. They measure the rider's pedaling force through strain gauges. These gauges can be installed at the bottom bracket or positioned on the rear wheel. When a torque sensor receives input, it measures the amount of force applied and sends that information to the controller. The controller then determines the motor's output level based on the rider's selected assistance mode (PAS).
Given that these sensors provide different signals to the controller, their operation differs as well. Cadence sensors set a fixed output for each assistance mode (PAS), whereas torque sensors adjust motor output based on the magnitude of the signal received.
Advantages of Cadence Sensors
Cadence sensors have distinct advantages, the most significant being their suitability for individuals who haven’t ridden a bike in a long time. Electric bikes with cadence sensors primarily rely on the rider’s chosen assistance mode to determine speed, making them ideal for those needing more support from their electric bike.
However, cadence sensors do have disadvantages. The most apparent drawback is the delay in motor activation; the rider must complete a half to most of a pedal stroke to start the motor, which can feel straining at takeoff. Additionally, electric bikes with cadence sensors are generally less efficient in battery usage than those equipped with torque sensors, resulting in shorter ranges at the same battery capacity.
Advantages of Torque Sensors
For those who have previously ridden electric bikes with cadence sensors, torque sensor electric bikes offer a more immediate power response. As soon as the rider begins pedaling, the motor will provide assistance. As the rider increases pedal force, the motor output also rises, giving the sensation of having "mechanical legs."
Torque sensor electric bikes are great for riders with a certain fitness level or those looking to gain fitness through cycling. Since the motor output adjusts based on the rider's effort, electric bikes with torque sensors typically have greater endurance at the same battery capacity.
Choosing the Right Electric Bike for You
Both cadence and torque sensor electric bikes have their own advantages and disadvantages, catering to different types of riders. The choice of which sensor to go for isn't about superiority; it's about the cycling experience the rider wishes to enjoy. Potential electric bike owners should consider their desired riding style, destination, effort level they are willing to exert, and the riding experience they hope to achieve.
If possible, it is recommended that riders take a test ride to experience the differences between these two sensors firsthand. Understanding these options will enhance the cycling experience and help you find the electric bike that best suits you!
