Bicycle Computer Sensors: Configuring Speed Sensors, Cadence Sensors, and Heart Rate Straps

Introduction

The data-driven trend in modern cycling training has made sensors standard equipment. A Garmin Edge bike computer alone only provides GPS positioning; pairing it with a speed sensor, cadence sensor, heart rate strap, and even a power meter builds a complete training data ecosystem. However, the selection, installation, and calibration of sensors directly affect data accuracy. This article starts from the working principles of sensors and provides systematic configuration recommendations.

Sensor Communication Protocols: ANT+ vs Bluetooth

Before diving into each sensor, let’s first understand the two major wireless communication standards:

ANT+ (Advanced ANT+):

• A low-power wireless protocol developed by Dynastream (now a Garmin subsidiary)
• A broadcast architecture that connects multiple sensors simultaneously; one transmitter can be read by multiple receivers at the same time
• The primary sensor protocol for many GPS bike computers in Taiwan (Garmin, Wahoo)

Bluetooth Smart (BLE):

• Supports direct pairing with smartphones, with higher adoption rates
• Point-to-point connection; one sensor typically pairs with only one device
• In recent years, many new sensors support dual ANT+/BLE protocols

Speed Sensor

The speed sensor measures wheel rotation speed and converts it into riding speed. It mounts on the front or rear wheel hub and uses a built-in accelerometer to detect rotation.

Necessity of the speed sensor:

On outdoor rides with GPS signal, the bike computer can calculate speed directly via GPS, making the speed sensor seem redundant. However, in the following scenarios, the advantages of a speed sensor are clear:

• Indoor trainers: No GPS signal on a trainer, making the speed sensor the only source of speed/distance data
• Tunnels/underpasses: When GPS signal is interrupted, the speed sensor maintains continuous data
• GPS error correction: In dense urban areas with GPS interference, the sensor provides more stable speed data

Mainstream speed sensors:

Product	Mounting Position	Battery Life	Protocol
Garmin Speed Sensor 2	Hub	~1 year	ANT+/BLE
Wahoo RPM Speed	Hub	~1 year	ANT+/BLE
Magene S3+	Hub	~1 year	ANT+/BLE

Cadence Sensor

Cadence is the number of pedal revolutions per minute (RPM) and is an important metric for evaluating pedaling efficiency. The cadence sensor typically mounts on the crank arm and detects rotation cycles.

Importance of cadence:

Research shows that for most riders with a training foundation, a cadence of 80-100 RPM is the most efficient range. Cadence that is too low (<70 RPM) with high resistance places greater impact on the knee joints; cadence that is too high (>110 RPM) saves muscular effort but increases cardiovascular load, requiring higher aerobic fitness.

Cadence training applications in Taiwan:

The steep gradients of Taiwan’s mountain roads (exceeding 10%) pose a major challenge for cadence control. Many beginner climbers grind at low cadence under heavy load, which is not only inefficient but also hard on the knees. It is recommended to maintain a minimum cadence of 70-80 RPM when climbing, paired with appropriate gear selection.

Some modern GPS bike computers (such as the Garmin Edge series) already have built-in accelerometers that can estimate cadence without an external sensor, but with slightly lower accuracy than a dedicated cadence sensor.

Heart Rate Monitor

Heart rate is the most direct physiological indicator for assessing exercise intensity, and is divided into two categories: chest straps and optical wrist/arm-based monitors.

Chest Strap Heart Rate Monitor

Working principle: Electrodes adhere to the chest skin and detect the heart’s electrical signals (ECG principle), offering extremely high accuracy.

Key advantages:

• Measurement accuracy approaches medical-grade ECG, with extremely low latency (<1 second)
• Unaffected by exercise intensity (remains accurate during high-intensity sprints)
• Supports HRV (heart rate variability) measurement (on select models)

Considerations for use in Taiwan:

• Taiwan’s hot, humid summers make chest straps less comfortable to wear
• It is recommended to wear the strap after moistening the skin (sweat is a good conductor and improves electrode contact)
• Clean after each use to extend electrode lifespan

Optical Heart Rate Sensor

Optical heart rate monitoring shines light onto the skin and detects changes in reflected light (PPG principle) to estimate heart rate. It is now integrated into some GPS bike computers (such as the optical sensor on the back of the Garmin Edge 1050).

Limitations of optical sensors:

• Skin movement during exercise creates noise, causing latency and errors in real-time data during high-intensity interval training
• Direct sunlight interferes with measurement
• For training that requires precise heart rate zone control, the chest strap remains the more reliable choice

Building a Complete Sensor System

Based on training depth, the following configuration tiers are recommended:

Basic tier (beginner riders):

• GPS bike computer (with built-in GPS)
• Heart rate chest strap
• Cadence sensor

Advanced tier (systematic trainers):

• GPS bike computer
• Heart rate chest strap (with HRV support)
• Cadence sensor
• Power meter (single-sided or dual-sided)

Competitive tier (race-preparing riders):

• Flagship GPS bike computer (with features such as ClimbPro)
• Dual-sided power meter
• HRV chest strap
• Speed sensor (for trainer use)

Sensor Calibration and Maintenance

• Speed sensor: Accurate wheel circumference must be entered (measure the actual circumference of the tire when fully inflated); an error of ±5mm will cause cumulative distance deviation
• Cadence sensor: Periodically confirm the distance between the magnet (if a magnet-based model is used) and the sensor (typically within 5mm)
• Heart rate strap: Rinse the electrode pads with clean water regularly; replace the battery annually (Garmin HRM series uses a 3.5V CR2032 battery)
• Pairing settings: When using the same set of sensors across multiple bikes, confirm that each bike computer is properly paired and that ANT+ or BLE mode is selected

Practical Recommendations

• Beginner starter kit: Garmin HRM-Dual (chest strap, ANT+/BLE dual protocol) + Garmin Cadence Sensor 2, approximately NT$3,500, is the most stable basic configuration
• Indoor training essentials: Speed sensor (hub-mounted) + smart direct-drive trainer, so that indoor speed/distance data is accurate
• HRV applications: If using an HRV-capable chest strap (such as the Garmin HRM-Pro Plus), measure resting HRV each morning to track training recovery status over the long term
• Sensor batteries: It is recommended to replace batteries one week before important events to avoid running out of power mid-race

Conclusion

The sensor system is the foundational infrastructure for data-driven training. From heart rate straps to cadence sensors, the data provided by each sensor is valuable information for optimizing training. For cyclists in Taiwan, building a basic sensor system and learning to interpret the data is more important than immediately purchasing the most high-end power meter. The value of data lies in analysis and application, not accumulation.

Related Reading

• Bike Computer Sensor Configuration: Installation and Setup of Speed, Cadence, Power, and Heart Rate Sensors
• Installation and Maintenance of Cycling Cadence Sensors and Speed Sensors
• Cycling Electronic Assist Systems: A Complete Integration Guide to Power Meters, Sensors, and Training Technology
• Monitoring Tools for Cycling Cardio Training: Accuracy Comparison of Heart Rate Straps vs. Optical Heart Rate