How do you Measure a Bicycle Tire? In 5 Easy Steps

So how do you measure a bicycle tire? To buy a spare or replacement tire for your bicycle, you need to identify the size of your bicycle wheels. Tire measurement related to bikes usually has two components. The more significant number is the diameter of the tire in inches. The smaller number is the breadth of the tire in inches. 

The diameter of your bicycle tire usually ranges from twelve to twenty-six inches. On the other hand, the breadth of the tire typically ranges from 1.75 to 2.2215 inches. The size of the bicycle tires is one of the most neglected aspects among casual riders.

The International Organization for Standardization, abbreviated as ISO, has designed another bike tire measurement system. This methodology uses millimeters to identify the breadth and inner diameter of the tire. As you can imagine, wheels are an integral component of bicycles. 

Not only do wheels allow you to ride smoothly, but they also guard your bicycle against bumps and potholes. A large majority of cyclists don’t know how to measure the bicycle tire. Here are some steps which would help you to calculate the tire of your bicycles.

How do you Measure a Bicycle Tire

What do the Numbers Imply?

How do you measure a bike tire? To be precise, the processes are pretty more straightforward only when you are aware of what the numbers imply. Before measuring the tires, it is imperative to know the value of the numbers. Bicycle tire measurements contain two separate parts. Always remember that the more significant digit is the wheel diameter. 

On the contrary, the smaller number is the tire breadth. The tire width is commonly denoted by inches and millimeters. The size of the tires varies based on the bike type. A majority of tire diameters fall between 12 to 26 inches. On the other hand, the breadths of the tire lie between 1.75 to 2.215 inches. Let’s find how do you measure a bike wheel.

Steps to measure your Bicycle Tire 

Here are some steps that would help you measure your bicycle’s wheels. 

1. Measure the Tire with the Standard Method 

To measure the tire with the standard method, you have to keep the bicycle in the upright position. When the bike is in the proper place, you will be able to measure the tires without the bike falling on you. If you are measuring the bicycle tire alone, always opt for a metal measuring tape. 

Measure the distance from the ground to the tire’s center point in inches. This measurement is also known as the radius of the tire. To calculate the diameter, you should multiply the radius by two. The diameter of a majority of adult bicycle wheels lie between 26 and 29 inches. In case the tire of your bike is mounted, you should check the wall to measure the diameter. 

You must measure the flat part of the wheel across the tread from one side to another. This measurement will provide you with the bicycle tire’s breadth. Note that width varies significantly on the use of the tire. If you want to ride your bicycle on rough terrain, always go for tires with wider treads. And while buying new tires for your bike, always specify diameter first, followed by the breadth.      

2. Using the ISO Method to measure the Tire 

So how do you measure wheel size on a bike with another method? A majority of riders love to measure their bicycle’s tires with the help of the ISO method. The ISO methodology uses millimeters to denote the size of your bike. Note that one inch equals 25.5 millimeters. You have to use a calculator to identify the total width of your bike’s tire in inches. 

To measure your bike’s tire with the ISO method; ensure that it is in the upright position. You should measure in millimeters from the center of the wheel to the inner edge of the tire. To calculate the diameter, double the figure. A vast majority of adult bicycle tires measured with the ISO system lie in the range of 650 to 700 millimeters. 

It is worth noting here that the ISO system includes both the Bead Seat Diameter or BSD and the tire’s width in diameters. 

Measuring the width of the tire with the ISO system is pretty straightforward. To measure the width, you should measure across the tread from one side to the other in millimeters. If you are buying a new tire with the help of the ISO system, you should list the width first, followed by the diameter.   

3. Calculate the Tire’s Circumference

You can measure a bike tire by calculating its circumference. Circumference refers to the distance of the outer portion of the bicycle wheel. Riders usually calculate the circumference of their bicycle wheel to calibrate the speedometer or computer of the bike. Let’s cite the example of a car to make you understand better. 

If you have changed the wheels of your car, then the speedometer and odometer will provide inaccurate data. If you are planning to install GPS on your bike, then measuring the wheel’s circumference is vital. You can calculate the tire’s circumference by multiplying the diameter by pi. 

If you are diligent with Mathematics in your school, then calculating the circumference of a circle is relatively easy. If you know the diameter of the bicycle tire, you can calculate the circumference rapidly. Do you know that you can now measure a bike wheel size by measuring the circumference with a string? 

If you are unaware of the diameter of the wheel, measure the circumference by wrapping a thread around the outside edge of the wheel. You can cut the string at the spot where it reaches the starting point. Subsequently, you should measure the thread’s length to identify its circumference.     

4. Measuring the Wheel Size Yourself 

In case you are unable to find the size marking on the tire, you can measure the wheel yourself. By measuring the diameter of the wheel in millimeters, you can deduce the equivalent of the ETRTO number approximately. The below table indicates the wheel size name and the equivalent ETRTO number. 

Size of the Wheel ETRTO or Rim Diameter
26″ / 650C559mm
20″ 406406mm
20″ 451 (Present in Old Fashioned Bikes)451mm
28″ 29er 700C622mm
27″ / 27.5″ / 650C584mm

5. Checking your Bicycle’s User Manual 

Every bicycle comes with a user manual. If you want to know the size of your bicycle’s wheel, you can go through the manual. If you are still unable to find the size of the wheels listed in the manual, contact the store from where you brought the bike. 

Bike stores have experts who will be able to tell the size of the tire by just looking at them. You can also visit the website of the retailer to access the detailed specifications of the bike.  

How do you Measure a Bicycle Tire Conclusion 

Reading bike tires is not that difficult if you are aware of the processes. With the help of the methods listed above, you can now measure the tire of your bikes whenever the requirement arises. The five ways stated above are easy to follow, and you’re good to go!

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.

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