Cadence Sensors: Optimal Placement, Types, and Installation for Cyclists

Which Crank to Put Cadence Sensor?

For most modern, accelerometer-based cadence sensors, the non-drive side (left) crank arm is the optimal and universally recommended placement. This ensures reliable data transmission, minimizes interference, and simplifies installation.

The Role of Cadence in Cycling Performance

Cadence, measured in revolutions per minute (RPM), refers to the rate at which a cyclist pedals. It's a critical metric for understanding and optimizing cycling performance, efficiency, and even injury prevention. Tracking your cadence allows you to:

• Optimize Power Output: Maintain a consistent power output by adjusting gears to match your preferred cadence range.
• Improve Efficiency: Find your most efficient pedaling style, reducing wasted energy and improving endurance.
• Reduce Fatigue: Higher cadences (within reason) often lead to less muscular fatigue compared to "grinding" in a high gear at low RPMs.
• Prevent Injury: Consistent, fluid pedaling at an appropriate cadence can reduce stress on joints and muscles.

A cadence sensor is the tool that provides this valuable data, relaying it wirelessly to your cycling computer, GPS watch, or smartphone.

Understanding Cadence Sensor Types

Before determining placement, it's crucial to understand the two primary types of cadence sensors:

• Magnet-Based Sensors: These older designs typically consist of two parts: a sensor unit mounted on the chainstay or seatstay, and a magnet attached to the crank arm (for cadence) and/or a wheel spoke (for speed). The sensor detects each pass of the magnet.
• Accelerometer-Based (Magnet-less) Sensors: These are the modern standard. They contain an accelerometer that detects the rotational motion of the crank arm itself. They are typically small, self-contained units that attach directly to the crank arm.

The vast majority of contemporary "crank-mounted" cadence sensors are accelerometer-based, and it is this type that the question primarily addresses.

Optimal Placement for Accelerometer-Based Cadence Sensors

For virtually all accelerometer-based cadence sensors designed to be attached directly to a crank arm, the non-drive side (left) crank arm is the preferred and recommended location.

Why the Left Crank Arm?

• Reduced Interference: The drive side (right) of the bike is cluttered with the chainrings, chain, and front derailleur. Placing the sensor on the non-drive side minimizes the risk of physical interference, accidental bumps, or contact with chain grease.
• Easier Installation and Maintenance: Installation on the non-drive side is generally simpler as you don't have to contend with the drivetrain components. It also makes battery changes or sensor removal easier.
• Consistent Signal Transmission: While most sensors transmit effectively from either side, many cycling computers and GPS devices are often mounted on the handlebars, providing a clearer line of sight to the non-drive side. This can contribute to more consistent and reliable data transmission.
• Standardization with Power Meters: Many single-sided crank-based power meters are also located on the non-drive side. Placing your cadence sensor here aligns with a common setup for advanced data collection.

Specific Placement on the Left Crank Arm:

• Most sensors attach to the inside surface of the crank arm, close to the pedal spindle.
• Ensure the sensor is positioned securely and does not interfere with your shoe, the frame, or any other components during your pedal stroke.
• Some sensors come with a rubber mount or zip ties for secure attachment. Always follow the manufacturer's specific instructions.

Placement for Magnet-Based Cadence Sensors

If you are using an older, magnet-based cadence sensor, the placement protocol is different:

• Sensor Unit: This typically mounts on the chainstay (the tube running from the bottom bracket to the rear axle) on the non-drive side.
• Magnet: A small magnet is then attached to the inside of the left crank arm.
• Proximity is Key: The critical factor is ensuring the magnet passes very close to the sensor (usually within 3-5mm) with each revolution of the crank arm. Adjust the sensor's position on the chainstay until this clearance is achieved consistently.

Installation Best Practices

Regardless of the sensor type, follow these guidelines for a successful installation:

1. Clean the Surface: Before attaching any sensor, thoroughly clean the crank arm or chainstay surface with rubbing alcohol to ensure a strong, lasting bond for adhesive mounts or to prevent slippage for rubber mounts.
2. Secure Attachment: Use the provided mounting hardware (rubber bands, zip ties, double-sided tape) as instructed by the manufacturer. Ensure the sensor is firmly attached and cannot shift during riding.
3. Orient Correctly: Some accelerometer-based sensors may have a specific orientation requirement (e.g., an arrow pointing forward). Consult your sensor's manual.
4. Pair and Test: After installation, pair the sensor with your cycling computer or device. Spin the cranks to ensure it's detecting cadence readings consistently. Perform a brief test ride to confirm functionality under real-world conditions.

Troubleshooting Common Issues

• No Cadence Reading:
  • Check battery levels in the sensor.
  • Ensure the sensor is correctly paired with your head unit.
  • Verify the sensor is securely mounted and oriented correctly.
  • For magnet-based sensors, check the magnet's proximity to the sensor.
• Inconsistent Readings:
  • Check for loose mounting, which can cause the sensor to shift.
  • Ensure no physical obstructions are interfering with the sensor's movement or signal.
  • Check for other wireless devices that might cause signal interference.

Conclusion

For optimal performance and ease of use, the non-drive side (left) crank arm is the definitive choice for mounting an accelerometer-based cadence sensor. This placement minimizes potential issues and ensures accurate, consistent data, empowering you to train smarter and ride more efficiently. Always refer to your specific sensor's instruction manual for detailed installation guidance.