Summary

A cadence sensor is a device used in e-bike systems to detect when and how fast a rider is pedaling. It signals the motor to engage once pedaling begins and adjusts motor support based on pedal rotation speed, enabling entry-level pedal assist functionality without requiring force-based input.

Key Facts

Introduced: Early 2000s
Category: Technology / E-Bike Systems
Also known as: PAS magnet ring, pedal cadence sensor
Used by / Found on: Entry-level to mid-range hub motor e-bikes
Location: Bottom bracket area or crank arm
Core function: Detects pedal rotation to activate motor assist
Primary benefit: Simple, cost-effective pedal assist activation
Common system pairing: Class 1 and Class 2 pedal assist e-bikes

Overview

Cadence sensors form the foundation of many electric bike pedal assist systems. While more advanced torque sensors offer a proportional, responsive assist experience, cadence sensors provide a simpler function: they detect whether the rider is pedaling and, in some systems, how quickly the cranks are turning. Based on this input, the e-bike’s motor controller applies assistance at a pre-set power level.

Often found on hub-motor e-bikes, especially in commuter, cruiser, and budget categories, cadence sensors allow electric assistance without requiring high force from the rider. Instead of measuring how hard the rider is pushing, these sensors merely detect whether pedaling is occurring. That makes them ideal for riders who want steady, predictable power delivery without too much complexity.

Though cadence-based systems are sometimes considered “less refined” than torque-sensing systems, they serve an important purpose. They make electric bikes more accessible to users with limited strength, mobility, or technical experience. With fewer moving parts and less reliance on firmware tuning, cadence systems are also easier to service and integrate into entry-level builds.

As e-bike adoption grows globally, cadence sensors continue to play a vital role—especially in regions where affordability, simplicity, and reliability are key design priorities.

How It Works

Cadence sensors operate on straightforward principles but are critical to the function of pedal-assist e-bikes. Here’s how the system typically works:

1. Magnet Ring + Sensor Pickup

The most common setup involves a ring of magnets attached to the crank or bottom bracket axle. A small sensor is mounted nearby, usually on the frame or motor casing. As the rider pedals, the magnets pass by the sensor.

Each time a magnet passes, the sensor detects a change in the magnetic field. These pulses tell the controller that pedaling is occurring. If enough pulses happen in succession (i.e., the cranks are rotating), the system activates the motor.

2. Crank Rotation Detection

Cadence sensors do not measure force—they only monitor rotation. Some sensors are binary: they turn the motor on when pedaling starts and off when pedaling stops. Others are multi-level, estimating pedal cadence and adjusting assist levels slightly based on how quickly the rider is spinning.

That said, most cadence sensors deliver pre-set levels of motor output, selected by the rider through a handlebar-mounted control unit. For example:

Eco Mode: 30% of motor power
Tour Mode: 70%
Turbo Mode: 100% or more

This keeps user interaction simple: pick your assist level, pedal gently, and enjoy the boost.

3. No Force Measurement

Because there’s no measurement of pedal pressure, cadence-based systems often feel less natural. Riders may describe the assist as “surging” or “on/off.” However, this trade-off is acceptable to many users in exchange for affordability, simplicity, and ease of use.

Strengths, Limitations & Comparison to Torque Sensing

Cadence sensors shine in certain use cases, but they also come with limitations. Comparing them to torque sensors helps illustrate the difference in ride experience.

Strengths

Affordability: Cadence sensors are cheaper to manufacture and integrate, making them common on budget e-bikes.
Simplicity: Fewer variables to tune, easier for non-technical users.
Ease of Start: Riders with low leg strength can still trigger assist with light pedaling.
Compatibility: Widely compatible with many hub motor systems and Class 2 e-bikes.
Low Maintenance: Minimal wear points and easy to replace or adjust.

Limitations

Less Natural Ride Feel: Assist doesn’t respond to how hard you’re pedaling—only that you’re pedaling.
Power Delay or Surging: Basic systems may delay assist when starting or continue pushing after pedaling stops.
Reduced Efficiency: Without nuanced control, they may use more battery on flat terrain.
Limited Terrain Adaptability: Not ideal for technical trail riding or steep climbing, where precise control is needed.

Compared to Torque Sensors

Feature	Cadence Sensor	Torque Sensor
Detects Pedaling Effort	❌	✅
Ride Feel	Mechanical, binary	Smooth, proportional
Motor Response	On/off or fixed levels	Adaptive, real-time
Cost	Low	Higher
Ideal Use Case	City, leisure, flat	Climbing, trails, sport
Common on	Budget e-bikes	High-end mid-drive e-bikes

Notable Implementations

Rad Power Bikes (Class 2 models): Most of their hub motor e-bikes use cadence sensors for throttle and PAS modes. Easy to operate and reliable across models.
Aventon Pace 350 / 500: These urban commuters use cadence-based pedal assist with user-selectable power levels.
Lectric XP Series: Popular folding bikes that combine cadence PAS with throttle control—great for urban and recreational riders.
Velotric Discover Series: Entry-level commuter bikes using cadence sensors tuned for casual pedaling and steady power delivery.
Heybike Cityscape / Ranger: Feature basic cadence sensors tuned for steady cruising on flat urban terrain.

These examples show how cadence sensors dominate the affordable e-bike market, where ease of use often outweighs premium ride feel.

Related Terms

Pedal Assist (PAS)
Torque Sensor
Throttle Control
Hub Motor
Class 2 E-Bike

References

Rad Power Bikes: Tech and Sensor Integration
Aventon Support: PAS Operation and Calibration
EBR: “Cadence Sensors Explained” – Review Breakdown
Shimano STEPS: Sensor Types and Assist Behavior
EbikeSchool.com: DIY PAS Sensor Installation and Tuning
Industry Whitepapers on E-Bike Classification and Sensor Impact
Cycling Industry News: Affordability Trends in E-Bike Design