Installing and Maintaining Bike Cadence and Speed Sensors

Introduction: Data Doesn’t Lie, But Sensors Do

You’re staring at your bike computer: 85 km/h, 250 RPM cadence. You know you’re not Peter Sagan, so the problem must be the sensor.

Sensors are the foundation of modern cycling training, but many riders install them and forget about them, only to start questioning their sanity when the data suddenly turns bizarre one day. Let’s talk about how to install and maintain your sensors correctly.

Types of Sensors

Speed Sensors

Cadence Sensors

Combo (Speed + Cadence) Sensors

Some products combine both speed and cadence functions:

Best value pick: The Magene S3+ combo sensor is available on Taiwan’s Shopee, costs about half of Garmin’s price, and is fully capable for the job.

Correct Installation: Speed Sensor

Hub-Mounted Installation (Using Garmin Speed Sensor 2 as an Example)

1. Choose the mounting location: front or rear wheel hub

   • Front wheel: more stable data (unaffected by rear wheel slippage)
   • Rear wheel: reflects actual driving speed

2. Clean the hub surface: wipe with alcohol to ensure the adhesive surface is clean

3. Choose the correct rubber pad: most sensors come with rubber pads of different sizes—choose the one that fits your hub’s diameter

4. Installation orientation: confirm the sensor’s marked direction matches the wheel’s rotation direction

5. Secure it:

   • Use the rubber strap to secure it first
   • Confirm it doesn’t touch the frame or brake caliper
   • Spin the wheel to test stability

Common Installation Mistakes

• Mounted too far out: touches the quick release lever or disc brake caliper
• Reversed orientation: causes unstable data
• Rubber strap too loose: it can fly off mid-ride
• Position offset: an angled installation affects sensing

Correct Installation: Cadence Sensor

Crank Arm Installation

1. Choose the mounting side: the non-drive side (left crank) is usually recommended

   • The drive side may conflict with the chain or front derailleur
   • The non-drive side has more clearance

2. Mounting location: the flat section of the crank arm, usually near the pedal end

3. Check clearance:

   • Doesn’t interfere with your shoes
   • Doesn’t collide with the frame
   • Doesn’t touch anything while pedaling

4. Securing method:

   • Rubber strap (included with most products)
   • Confirm the rubber strap won’t loosen over time
   • Zip ties can be used for extra reinforcement

Calibration After Installation

Speed sensor calibration:

1. Enter the correct wheel diameter into your bike computer
2. Common wheel diameter reference:
   • 700x23c: 2096mm
   • 700x25c: 2105mm
   • 700x28c: 2136mm
   • 700x32c: 2155mm
3. Most accurate method: actually measure the distance covered by one full wheel rotation

Cadence sensor calibration:

• Usually no special calibration needed
• Pedal a few rotations on first use to let the sensor calibrate its orientation

Pairing and Connection

ANT+ vs Bluetooth

Pairing Steps

1. Activate the sensor (usually wakes up when the wheel spins or you pedal)
2. Search for the sensor on your bike computer
3. Select the correct sensor ID
4. Confirm the data is displaying correctly
5. If you have multiple bikes, remember the IDs of the different sensors

Care and Maintenance

Regular Inspection (Monthly)

1. Check for looseness: is the rubber strap still secure?
2. Check for position drift: has the sensor shifted?
3. Clean the surface: wipe off dirt and moisture
4. Battery level: check the battery status on your bike computer

Battery Replacement

Most sensors use CR2032 coin cell batteries:

• Lifespan: typically 6–12 months (depending on usage frequency)
• When to replace: unstable data, difficulty pairing, sensor won’t wake up
• Replacement steps:
  1. Twist open the battery cover with a coin
  2. Remove the old battery
  3. Check that the waterproof O-ring is intact
  4. Insert the new battery (mind the polarity)
  5. Screw the battery cover back on

Note: You may need to re-pair the sensor after replacing the battery. If the O-ring has degraded or is damaged, be sure to replace it, or waterproofing will fail.

Waterproofing Notes

Taiwan has a lot of rain, so a sensor’s waterproofing matters:

• Most sensors have an IPX7 waterproof rating
• But the battery cover’s O-ring degrades over time
• Check the O-ring every time you replace the battery
• If you ride frequently in the rain, check the seal every 6 months
• Don’t spray the sensor directly with a high-pressure water jet

Troubleshooting Data Anomalies

Speed Data Anomalies

Cadence Data Anomalies

Practical Tips for Taiwanese Riders

1. CR2032 batteries are sold at every PX Mart: no need to go to a specialty electronics shop
2. Keep a spare battery in your saddle bag: a dead sensor on race day is extremely frustrating
3. Dry off your sensors after riding in the rain: especially around the battery cover
4. Batteries drain faster in winter: riders in northern Taiwan should take note
5. Magene and iGPSPORT offer the best value in Taiwan: their functionality is comparable to Garmin’s

Conclusion

Sensors are the foundation of your training data. Installing and maintaining them correctly ensures your training data is accurate and reliable. Take the time to set up your sensors properly, and every training record you log will actually mean something.

Next time your bike computer shows you riding 200 km/h, don’t rush to take a screenshot to brag—check your sensor first.

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