Tips for turning your phone into a cycle computer

Three Key Points for Using a Smartphone as a Cycle Computer

When using your smartphone as a cycle computer, the three most important factors are:

1. Enhancing and expanding data collection accuracy
2. Battery life
3. Mounting it in a visible and accessible position on your handlebar

If you can meet these three requirements, your smartphone can perform just as well as a high-end cycle computer.

Improve Data Accuracy and Variety by Adding Bluetooth Sensors

The most critical point in turning your smartphone into a cycle computer is the addition of external sensors.

Although it is possible to use your smartphone alone like a cycle computer, adding sensors allows you to collect data that smartphones alone cannot, and also improves the accuracy of data that is otherwise less precise when collected by the smartphone only.

Measure Speed Accurately with a Bluetooth Speed Sensor

Most cycle computer apps on smartphones obtain speed data using GPS. This allows for measurement of speed, distance, and travel time using location data—without any additional devices.

However, the downside of using GPS-based speed data is the inconsistency in accuracy depending on the riding environment.

Smartphones calculate speed using the formula “distance from point A to point B ÷ travel time,” but due to signal delays or inaccuracies in GPS reception, these points can shift.

This issue stems from the way GPS works—receiving signals from satellites. Environments such as urban areas with tall buildings or trails covered with trees can block or reflect GPS signals, leading to discrepancies. Depending on the quality of the GPS sensor and the riding conditions, discrepancies of up to 5 km/h are not uncommon.

To get more precise speed data, adding a Bluetooth speed sensor is your best option. Bluetooth speed sensors calculate speed based on wheel revolutions, so the measurements are unaffected by riding environment.

Get Cadence and Heart Rate Data That Your Smartphone Alone Can’t Measure

Once you get used to cycling, you’ll start wanting more metrics beyond just speed. For road biking and training, cadence, heart rate, and power are the three main performance indicators. Unfortunately, these cannot be measured with just a smartphone and a cycle computer app.

However, by adding Bluetooth sensors, you can collect cadence and heart rate data—metrics that smartphone apps alone cannot capture. Measuring cadence and heart rate allows for more in-depth data tracking, making your ride and training sessions more efficient and productive.

To measure power, you’ll need to install a power meter on your bike. Power meters typically cost tens of thousands of yen even for entry-level models, making them a less accessible upgrade for casual users.

Some Apps Can Use Apple Watch for Heart Rate Data

Depending on the app, some iOS cycle computer apps can retrieve heart rate data directly from an Apple Watch.

Heart rate sensors can be expensive (often over 10,000 yen), so having an Apple Watch that serves other purposes can be a practical and cost-effective option.

Improve Battery Life

Use a Battery Case or a Rechargeable Bike Light

The biggest weakness of using a smartphone as a cycle computer is battery life.

When used as a cycle computer, your smartphone’s screen and GPS are constantly active, draining the battery quickly. In some cases, it may last only around 3 hours—far from enough for a long ride. To solve this, you’ll need to extend the battery life.

Connecting your phone to a power bank stored in a top tube bag is one option, but it carries the risk of water damage during sudden rain. A better solution is to use a battery case or a bike light with built-in charging capability.

When choosing a battery case or rechargeable light, aim for one with a battery capacity about three times that of your smartphone. For example, newer iPhones have around 3,000mAh internal batteries, while older models like the iPhone 8 have around 2,000mAh. A case with at least 5,000mAh is a good starting point.

Note that using a battery case frequently can degrade your internal battery, so using official accessories is recommended.

Enable Dark Mode

Dark mode reduces the power consumption of your screen’s backlight by using a black-based interface. This helps extend battery life.

Since the screen stays on continuously when using your smartphone as a cycle computer, choose an app that supports dark mode for maximum battery efficiency.

Use Offline Mode

Some cycle computer apps offer an “offline mode” that limits background data usage.

When offline mode is enabled, the app uses only GPS and sensor data, reducing network-related battery drain and improving overall battery longevity.

Mount Your Smartphone in a Visible Position on the Handlebar

Holding your smartphone while riding a bike is not only dangerous but also illegal in many regions. If you’re planning to use your smartphone as a cycle computer, a smartphone mount is absolutely essential.

When choosing a smartphone mount, make sure to consider:

1. The durability of the product, especially the arm and bracket components
2. Compatibility with your smartphone’s size

Frequently Asked Questions About Turning Your Smartphone Into a Cycle Computer

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