How Do Speed and Cadence Sensors Work? (How to Install One)

Biking is a great hobby, but for many people, it can also be a means of getting their daily physical exercise. And to help people make sure that they are getting the right amount of physical activity through biking, technology can help.

Cadence sensors and speed sensors are great tools for any biker to track properly how much they are paddling and active. But it’s normal to wonder how does a speed or cadence sensor work? And today, we will learn just that.

But before that, let’s get a clear idea about what a cadence sensor and a speed sensor are.

1. What Are Cadence and Speed Sensors?

Cadence and speed sensors are amazing products for any bike enthusiast. It is like those smart helmets that make your bicycling experience richer. Even though their functions have a lot of similarities, they are not exactly the same.

1.1 What Is a Cadence Sensor?

As you might be able to guess from the name, the cadence-only sensor can count the number of rotations per minute you make with the paddle while riding the bike. By measuring cadence, one can estimate the output of the energy spent during the cycling session.

It has a sensor and a magnet set on the crank arm in order to measure the cadence of the bike. But most new sensors don’t use magnets anymore. The unit basically detects the RPM of the arm of the crank—when the arm passes the sensor.

1.2 What Is a Speed Sensor?

The speed-only sensor is able to give you an assessment of the speed of the bike. Not to mention the distance you have passed by doing mathematical calculations based on the wheel circumference. It is set with the help of a magnet on the rear wheel of the bike.

Now the cadence-only sensor and the speed-only sensor are great for people who need them individually. But the best option is the combination of both speed and cadence sensors in a bundle. And so, it is the most popular nowadays.

2. How Does a Cadence Sensor Work?

The cadence sensor used to be made differently. There were three major parts of the cadence sensor. But now, this design is not used anymore.

It had an electronics pod, and on the two sides of it, there were two magnets. One is the cadence magnet, and the other is called the spoke magnet. The electronics pod stayed mounted on the frame of the bike.

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Since there were two magnets on the sides of the pod, it contained two magnet sensors enabling it to measure both speed and cadence simultaneously. If the magnet passed the pod, a rotation was counted. This is how cadence sensors are used to work with outdoor bikes and indoor bikes.

But nowadays, things are different; the cadence sensor simply uses an internal accelerometer to measure and determine the wheel’s rotation. This eliminates the need for any magnet—making the installation and working process much easier.

This makes the sensor a lot more accurate as well. Most newer models of cadence sensors go for this magnetless approach instead of the traditional method.

3. How Does a Speed Sensor Work?

The device is made of a sensor for the wheel and a magnet. Since the circumference of the wheel is known, every time the magnet passes the wheel sensor, the distance and the overall speed can be determined.

This is how the speed is estimated using the size and the measurements of the wheel. It can also measure the cadence of the bicycle to a certain extent.

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Most modern and newer models of these can connect with your phone and display all the details measured through a compatible app.

From the point you put your foot on the pedal, it starts counting your input, and it will continue until you stop, giving you a complete set of information that you can use to reach your fitness goal.

4. Why Use a Combination of Cadence and Speed Sensors?

A cadence sensor can measure the speed of your bicycle when you are pedaling it, but it will not be as accurate of a reading as the speed sensor. At the same time, a speed sensor can also measure the cadence to a certain degree, but not entirely accurate.

For a cadence sensor, the wheel speed will be considered for a 3:1 gear ratio regardless. And for the speed-only sensor, the cadence will be considered for a 1:3 ratio irrespective of the actual gear.

To get both of the readings in the most accurate way possible, it is recommended to use a bundle of both types of sensors and get the actual data that you might search for.

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5. How to Install Cadence Sensor on an Outdoor Bike

The cadence sensor will be attached to the crank arm of your bicycle. Now some sensors will come with bands and some with a cable tie system that can hold the device in place.

It might even ship with a sticker if you want to mount it permanently—so that you never miss measuring cadence while you are pedaling your bike.

If it is a band, choose the band that will go around the crank arm of your bike suitably and tightly. And make sure that the device is on the back side of the arm so that it does not cause unwanted contact with your heels.

And if it is a cable tie system, it really is not that much different. Just tighten it as much as you need to keep the device on the other side. Then, cut the hanging excessive cable tie off.

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6. How to Install Cadence Sensor on an Indoor Bike

If you have an indoor stationary bike, it is literally the same process. Fix the cadence sensor on the indoor shaft bike, and you will get the right readings.

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7. How to Install Speed Sensor on an Outdoor Bike

The speed sensor should be put on the wheel. You can put it on the front of the rear wheel if you want, but the positioning won’t have much effect on the calculations.

You will attach the sensor to the hub of your bike’s wheel with the band it comes. Wrap the sensor connected with the band around the hub and push from the other side until it gets set.

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8. How to Install Speed Sensor on an Indoor Bike

Fit the speed sensor on the axle of the wheel. Make sure the sensor device can be mounted comfortably and it does not get struck by the forks of the stationary bike while rotating with the axle.

Now be it an outdoor or an indoor bike, for the speed sensor to work, you have to know the wheel circumference. 

For an outdoor bike, lay a measuring tape on the ground. Mark a spot on the tire and run the bike on that very point. Keep moving until you reach that point on the tire to find the circumference of the wheel. Then, add that info in the app since the math is done based on it.

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For an indoor or stationary spin bike, take a spot on the wheel and carefully wrap a measuring tape around it to calculate the circumference.

If that seems too difficult, you can just measure the radius of the wheel and multiply it by 6.28 to get an estimate of the circumference. You can also do it with an outdoor bike if you wish.

9. Why Use Cadence and Speed Sensors?

As mentioned before, if you cycle just as a hobby, you most likely would not need a sensor. But if you take it as something more serious than a pastime and want to get the full benefit from your biking sessions, they are essential for you.

In order to keep fit, it is vital to know information related to the cadence of your ride, the speed at which you are riding, and the distance you have covered. These will help you be closer to your goal.

If your sensor detects that you are not going fast enough, you can pedal more quickly and reach a higher cadence. This is done by increasing the wheel rotation number per minute by applying more pressure.

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Additionally, if your speed is not high enough and you feel the need to burn more calories, it can help you reach there as well. Overall, the sensors are extremely helpful for serious bikers. You can get the functionality of an e-bike without even owning one.

However, an electronic bike can barely be a good option for keeping you fit since most good ones use torque sensors. It basically measures if more or less power is needed to be provided electronically to keep the bike moving—based on the pedaling of the biker.

10. How Accurate Are Speed Sensors?

Cadence sensors and speed sensors are individually really effective. The newer cadence sensor devices’ internal accelerometer is amazing at cadence calculation.

And, if you can measure the circumference of the wheel correctly, the speed sensor is adequate in giving you the most accurate results.

That is why bundles of speed and cadence sensors are the most popular in the market among fitness enthusiasts. However, not all of them are good enough to provide you with data with precision.

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So, if you are in search of some good options, we have that covered for you as well.

11. Products That We Recommend

Out of all the bundles in the market, we could shrink it down to two products from our own experience and research.

Do note that there are smart indoor bikes on the market which are equipped with cadence, speed, and many other sensors by default. If you happen to have one of those, you might not need these sensors.

01.

Wahoo Speed and Cadence Sensor Bundle

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This bundle is one of the best out there. It can mount on most bikes very easily thanks to the cable tie system for the cadence sensor and the band system for the speed sensor. And it is extremely easy to set up as well.

It can track and capture the cadence and speed of the bike in real-time and connect wirelessly with any smartphone, tablet, or bike computer made by major manufacturers.

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To see that the sensor is working, it even has LED lights to indicate that. The blue light is for the sensor connection, and the red light shows the detection of the cadence of the bike.

And most importantly, just like most of the newer and higher-end cadence sensors, it goes for a magnetless design. And it relies totally on the sensors inside to measure the cadence of the bike. This doesn’t only make it versatile but also easier to use.

02.

Garmin Speed Sensor 2 and Cadence Sensor 2 Bundle

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Garmin offers bands with their cadence and speed sensors which also come in three different sizes as per the needs of different bikes. This makes the devices really easy to mount to any bike you have with different sizes of crank and wheel hubs.

It sends live data about the speed, cadence, and distance via ANT and Bluetooth to compatible apps or displays, giving you a headstart.

The speed sensor also has an odometer feature to enhance the distance tracking mechanism.

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And just like the modern and high-end sensor it is, the design is totally magnetless and reliant on the internal sensors to determine the cadence of the bike—making it elegant and user-friendly.

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