Bike Sensors Explained: Speed, Cadence & Torque — The Ultimate Guide for Smarter Cycling

 If you’ve ever wondered how your cycling computer tracks your mph, or how e-bikes adjust power as you pedal, the answer lies in three tiny but powerful devices: speed sensors, cadence sensors, and torque sensors. Whether you’re a casual commuter, a weekend warrior, or a competitive cyclist, understanding these bike sensors can transform your rides—helping you track progress, optimize performance, and make e-biking feel more natural. In this complete guide, we’ll break down what each sensor does, how they work, pros and cons, and which one (or combination) is right for you.

Why are bike sensors important?

• Performance Tracking: Sensors give riders real-time data (speed, cadence, power, distance) for training and improvement.
• Motor Control (ebikes):Sensors tell the controller when, how much, and how smoothly to apply motor assistance.
• Efficiency: Smarter assist saves battery power and reduces strain on the motor.
• Safety & Comfort: Smooth acceleration, controlled speed cut-offs, and predictable behavior.
• Customization: Riders can adjust assist levels, training zones, and even diagnose bike performance.

Detailed explanation of the three core sensors

1. Speed Sensor:

A speed sensor is a bike accessory that measures your riding speed and distance by tracking wheel revolutions. Unlike a cadence sensor (which measures how fast you pedal), a speed sensor focuses on how fast the bike itself is moving.

How It Works

• Magnet-based type (classic):  small magnet attaches to a spoke, and the sensor mounts on the fork. Each wheel revolution is detected to calculate speed.
• Wireless accelerometer/gyro type (modern): No magnet needed. It mounts on the wheel hub and uses internal motion sensors to track speed.

The sensor transmits data via Bluetooth or ANT+ to a bike computer, smartphone app, or eBike display.

Why It’s Useful

• More accurate than GPS in tunnels, forests, or poor signal areas.
• Essential for indoor training on stationary trainers (since GPS doesn’t work indoors).
• Helps track performance and ride logs.
• On eBikes, the speed sensor often works with the motor controller to regulate pedal-assist cut-off (for example, many systems limit assist above 25 km/h in the EU or 28 mph in the U.S.).

2. Cadence Sensor:

A cadence sensor is a device used on bicycles to measure the pedaling rate (cadence), expressed in revolutions per minute (RPM). It tells you how fast you are turning the pedals, not how hard you’re pushing.

How It Works

• Magnetic/optical sensor (basic type): A magnet is attached to the crank arm, and the sensor is mounted near the bottom bracket. Each pedal rotation triggers the sensor to record cadence.
• Accelerometer-based sensor (modern wireless type): No magnets are needed; it uses motion detection to calculate RPM.
• Typically connects via Bluetooth or ANT+ to bike computers, smartphones, or eBike displays.

Why It’s Useful

• Efficiency: Helps riders maintain an optimal cadence (usually 70–90 RPM for most cyclists) to avoid fatigue.
• Training: Useful for structured workouts (e.g., high-cadence spin training).
• eBikes: Some pedal-assist systems use cadence sensors (or torque sensors) to regulate how much motor assistance to provide.

3. Torque Sensor:

A torque sensor is the most advanced type of sensor used on eBikes and high-end custom builds. Unlike a cadence sensor (measures how fast you pedal) or a speed sensor (measures bike movement), a torque sensor measures how hard you press on the pedals and tells the motor to match your effort.

How It Works

• The sensor is usually built into the bottom bracket, crankset, or rear dropout.
• It detects the force (torque) you apply to the pedals and converts it into an electrical signal.
• The eBike controller then delivers motor power proportionally to your pedaling force, making the ride feel natural.

Why It’s Useful

• Natural Riding Feel: Feels like your own legs are stronger, not like the bike is pushing you.
• Efficient Power Use: Motor only gives what you need, extending battery life.
• Great for Hills & Starts: Smooth power delivery prevents jerky launches or over-assist.
• Preferred by Enthusiasts: Higher-end eBikes use torque sensors for a premium ride quality.

Comparison of Sensors

Sensor Type	Measures	Ride Feel	Cost/Complexity
Cadence	Pedal RPM	Simple, on/off assist	Low
Speed	Wheel RPM	Regulates assist limit	Low
Torque	Pedal Force	Smooth, natural assist	High

 

Tracer Sensor Applications for Electric Bike

Raptor Pro DS

As a long-distance cruising e-bike, its integrated speed + torque sensor is key, working with the 800W motor and Samsung 48V/20Ah battery to optimize rides.

• Sensor Logic: Speed sensor tracks real-time speed (up to 30mph) for the color display; torque sensor detects pedal force. Together, they enable 3 riding modes + 5 assist levels: boosts assist for climbs (smooth with dual suspension/FAT tires) and cuts it for flat roads to save battery (55-65 miles range).

• Safety & Control: Sensor data (speed/assist) on-screen; speed sensor triggers sensitive 180mm hydraulic brakes at >25mph. Ideal for users wanting power + comfort on long rides.

Beyond Pro

This vintage-style urban e-bike uses an integrated speed + torque sensor with 800-1000W motor and LG 48V/17.5Ah battery.

• Urban-Focused Sensor Use: Torque sensor is sensitive—light pedal taps trigger low assist in NYC/LA traffic (avoids jerks); speed sensor logs speed (up to 25mph, U.S. compliant) and mileage for LED screen. Range: 30 miles (pure electric), 55-65 miles (assisted).

• Design Integration: Sensor’s 3 assist levels adapt to relaxed high-handlebar posture (prevents back fatigue); quick assist boosts for city slopes. Low sensor power + 4-6hr charge suit daily commutes. Perfect for style-focused urban riders.

What Dual Sensors Mean

1.    Cadence + Speed Sensor (most common)

Measures how fast you pedal (cadence) and how fast the bike moves (speed).

Why important:

• Gives the controller more precise info → avoids situations like ghost pedaling (spinning pedals without moving).
• Useful for basic eBike assist control and training apps like Zwift.

2.    Torque + Cadence Sensor (higher-end systems)

Measures how hard you push and how fast you pedal.

Why important:

• Motor assistance feels much smoother and more natural.
• Perfect balance between detecting effort and rhythm.
• Many mid- to high-end eBikes use this combo.

3.    Torque + Speed Sensor (less common)

Measures pedal force and bike speed.

Why important:

• Allows the motor to fine-tune power delivery based on both effort and actual ground speed.
• Often found on performance or racing-oriented builds.

Benefits of Dual Sensors

• Accuracy: More data points → better performance tracking.
• Smoothness: Eliminates jerky starts or unnatural power surges.
• Efficiency: Motor gives just the right amount of assist, saving battery.
• Safety:Speed sensor ensures cut-off limits are respected; cadence/torque prevents runaway assist.

Ideal Users for Dual Sensors

• Fitness-Focused Riders: Those who want to monitor both efficiency (via cadence) and speed. For example, a rider training for a century ride can use cadence data to stay in the 80-90 RPM sweet spot (reducing knee strain) while tracking speed to ensure they hit their 12-15 mph target pace.
• All-in-One Riders (Commute+Training): Users who bike to work and squeeze in training sessions. For commutes, speed data optimizes route time (e.g., “15 mph average to beat traffic”); for post-work rides, cadence data refines form (e.g., “fix low 60 RPM pedaling to avoid fatigue”). Dual sensors eliminate the need to switch between equipment for different rides.

Buying Guide

The key is to choose the right combination of sensors for your specific cycling needs.

Cycling Type	Recommended Sensors	Why It Works
Urban Commuting	Speed Sensor	Tracks trips & time
Fitness / Training	Cadence + Speed	Efficiency + pace
eBike / Daily Commute	Torque + Speed	Natural assist + safety
Pro / Performance	Power Meter + Cadence + Speed	Precision + racing data

 

 

Conclusion

Bike sensors are the foundation of smarter, safer, and more enjoyable cycling. Speed sensors give commuters accurate tracking, cadence sensors help fitness riders refine efficiency, and torque sensors deliver natural assist for e-bikes and pros. For most riders,dual-sensor setups strike the best balance-combing precision, smoothness,and value.Tracer Raptor Pro DS and Beyond Pro show how sensor integration elevates both-distance cruising and urban commuting.The key is matching the right sensor or combination to your riding goals,turning every trip into a more efficient, comfortable,and intentional experience.

 

FAQ — Frequently Asked Questions

Q1: Can GPS replace bike sensors?
A: Not completely. GPS can be inaccurate in tunnels, forests, or dense urban areas, and it doesn’t work for indoor training. Sensors are more precise and also save your phone’s battery.

Q2: Is a torque sensor really worth it?
A: Absolutely for e-bike riders. Torque sensors provide instant, natural-feeling pedal assist, especially when climbing hills or riding against headwinds.

Q3: Do bike sensors require maintenance?
A: Minimal. Just keep them clean, ensure the magnet and sensor are properly aligned, and replace the battery every 6–12 months (depending on usage).

Q4: Can I install sensors myself?
A: Yes for speed and cadence sensors—they are DIY-friendly. Torque sensors, however, are usually factory-integrated into e-bikes and not designed for aftermarket installation.