How To Measure Your Bicycle Tire For Bike Computer? (SETUP CORRECTLY)

Owning or buying a good bike computer is a clear sign that you are looking to take cycling seriously. The bike computer can enable you to improve your cycling performance and you will have clear data on your performance. However, many people ask the question of how to measure your bicycle tire for a bike computer to be installed.

After you have bought your bike computer, the next step would be to set it up. However, the setup might not be so easy if you are a new rider. To ensure accurate data, you want to make sure that you have the measurements for your wheel circumference. This will make positioning easier when setting up the bike computer.

Since the process might be daunting for some, we have stepped in to help you plan and set up the bike computer correctly. This article aims to provide you with a detailed guide to accurately setting up your bike computer. We will also look at some noteworthy charts that could guide you in the process of installation.

How To Measure Your Bicycle Tire For Bike Computer

Why You Need To Measure Wheel Size Before Setting Up Bike Computer

If the bike computer is not correctly set up on your bike, it is hard to ensure that every revolution provides accurate data. You need to ensure the bike computer is mounted correctly to indicate a full revolution on the tire. This will provide clear and accurate data that could support your performance. Here are some of the most important reasons why it matters:

  1. Accurate Data: One of the first reasons is to provide you with clear and direct data. You should make sure that you have accurate data that helps you improve your performance and your overall cycling ability. 
  2. Functionality: Another important reason is that your bike computer might not work as intended if the setup is not correct. You need to make sure that you set up the bike computer in a way that makes it usable.
  3. Monitor Certain Functions: Finally, many bike computers are more complicated than simply measuring basic data like speed. If you have an advanced bike computer like the Garmin Edge 830, you could also need accurate setups to measure things like cadence correctly.
We earn a commission if you make a purchase, at no additional cost to you.
12/01/2022 02:08 pm GMT

Numerous other reasons would pique the interest of professional cyclists as to why you need the correct setup for your bike computer, but these are the most important for amateurs. As you improve your cycling skills, you could be looking at new and revolutionary methods to provide even more data.

How To Set Up Your Bike Computer Correctly

Now that you understand the importance of a bike computer that is set up correctly, you also need to understand how the setup process works. There are three different methods you can use to ensure an accurate setup for your bike computer. We have broken them down to ensure you can use them for your setup.

  1. Calculating Wheel Size With A Formula

In the modern era, scientists and specifically the top physicists have made it easier for us to calculate the wheel size of a bike with the use of a formula. The first method is slightly easier than some of the following methods and would involve basic calculations based on some of the measurements of the wheel you have taken.

You can start by measuring the bike tire and using the folding rule to find the radius of the tire. Keep in mind that you would want to inflate the tires to the optimal level of inflation that ensures it is correct for you to ride with. Once you have all the numbers, you can use the following formula to help you calculate the circumference without full measurement:

U = 2 * pi *r

The formulation would give you the circumference of the tire in mm, which can then be translated to whichever measurement method you need to use for setting up your bike computer. 

  1. Physical Measurement Of Wheel Circumference

The second method tends to be the more accurate of the three methods. However, it does require a lot more work for you to do it correctly. You will need to have your bike computer on hand and some chalk with a rule or measuring tape that could measure the full rotation of the wheel on the ground.

You should start by making sure the tires are inflated to the designated PSI that you will be using when you ride the bike. Once done, you can use the chalk to make a marking on the tire and the ground where the wheel is pointing directly to the ground.  The bicycle valve is often a good place to use as a marker.

Next, you should roll the bike forward slightly until the section you have marked is pointing directly to the ground once again. If you have made a second mark on the ground, you will need to measure the distance traveled with the use of a measuring tape. By using the folding rule or dividing the number by half, you will find the radius.

Finally, you could simply enter the number into your bike computer, which should enable you to set up the computer with the correct data. Once you have entered the correct data, it should be much easier to set up the bike computer and ensure that all the stat tracking is accurate when you are riding your bike.

Using The ETRTO Table To Measure Circumference

The final method is slightly easier and you will find the ETRTO is used by many riders due to how easy it is to integrate the method. ETRTO or The European Tyre and Rim Expert Organization have developed a chart whereby a specification is indicated to measure the approximate circumference of your bike wheel.

Keep in mind that these are mostly approximations and it is hard to determine how accurate the ETRTO measurement method is due to various manufacturers that might have the same numbers, but the wheels can slightly differ. The ETRTO table is often included in the packaging when you buy your bike or bike computer in many European countries, but it might not be 100% accurate.

With the table, you can use the number in inches for your bike tire and find the ETRTO number, which should be in the following format; xx-xxx. The first two numbers are the tire width in millimeters, while the second set of numbers is the inner diameter of the tire, also in millimeters.

You can enter this information into your bike computer, allowing you to adjust your bike and tire setup to your needs. Once you have the overall circumference of the bike computer, you can use it to correctly and accurately measure the speed of the bike and the performance that you are currently going at.

Which Method Is The Best?

One of the most important questions we get asked a lot is which method is the best and which one should you use. While the second method feels the most accurate due to you doing all the measurements manually, many prefer the ETRTO method. However, we have seen slight deviations when wheels have the same ETRTO number from different manufacturers.

As for the first method, it is mostly based on guessing and you might not be accurate in terms of your setup when using it.

Overall, we would suggest that the second method is the most accurate and you will be doing all the calculations manually. Yes, it might take you longer, but once you have these measurements and the correct wheel circumference, it is much easier to enter the correct data into your bike computer. Eventually, it will help you, especially when measuring things like cadence.

Does It Work The Same For Road Bikes And Mountain Bikes?

Depending on the method you choose to use, you can use it for road bikes or mountain bikes. However, the size of road bikes is often indicated in CC and this means you will need to convert it back to inches or millimeters. 

If you are going to measure the wheel size on a good road bike, you should consider using the second method. To ensure overall accuracy, you want to use a piece of chalk or even some droplets of white paint to help you measure the wheel circumference correctly.

Overall, the second method is the best for any bike you have and especially when you are looking to mount a bike computer and accurately measure your data.

How To Measure Your Bicycle Tire For Bike Computer Summary

Since the advent of the bike computer, cycling has changed forever. With more data at our disposal and an easy way of measuring this data, many people are turning to bike computers. You can use these three methods to ensure your bike computer is set up to provide the most accurate data. Let us know in the comment section how you calculate your wheel circumference.

About Martin

I am Martin, I am the author of this blog. My main interests include cycling. That's why this blog was created. I have always been interested in technology and how bicycles are made, so I built one myself.

Leave a Comment