Tutorial: How to Measure Bike Tire Sizes (Easy)

Are you someone who owns a bike and wants to replace your old tires but can’t find the right size for your bike? Well, the reason must be that you’re measuring your bike tire size the wrong way. 

Bike tires are often neglected but they are an essential part of the bicycle because they are the reason for your smooth cycling experience. Here’s how you can measure bike tire sizes easily:

  • Secure the wheel first
  • Measure the diameter of the wheel
  • Measure the width of the wheel
  • Finally, combine the two measurements

When it comes to finding the right size tire for your bike, things can get slightly confusing.  

Usually, you can just look at your old tire and get the same size and it will be fine but occasionally the old tire might not be available so when you try putting on the new tires on your bicycle wheel, you will face trouble. 

Therefore, understanding bike tire sizes come in handy in these situations. To help you with this predicament, I will explain all the bike tire sizing systems as well as how you can easily measure your tire at home with the help of some basic tools. 

What Do Bike Tire Size Numbers Mean?

The bike tire measurements contain two parts in general.  The greater number signifies the tire diameter in inches, while the lesser number signifies the tire width in inches. The sizes are in inches most of the time, however, sometimes you may even find them in millimeters. 

Tire diameters typically range from 12 to 26 inches, with tire widths ranging from 1.75 to 2.215 inches which may vary depending on the bike type. 

For people’s better understanding, bike tire systems are divided into two tire size systems.

The first section comprises a standard or the traditional sizing system, while the second section includes the ISO approach.

» Maybe this also could be of interest to you: What Bike Size to Get?

How Do I Know My Bike Tire Size?

You can find your bike tire size to check the sidewall of your current tires. There should be a number that looks something like this: 700x23c. The first number is the diameter of your wheel in millimeters, and the second number is the width of your tire in millimeters.

The easiest way to find your bike tire size is to check the bike’s manual. You can find your bike’s manual online by visiting your bike manufacturer’s website.

  1. Go to the bike manufacturer’s website.
  2. Find the “Support” or “Customer Service” section of the website.
  3. Find the link to “Owner’s Manuals” or “Product Instructions.”
  4. Select your bike model and year from the list of manuals provided.
  5. Download the owner’s manual or product instructions in PDF format.
  6. Locate the section on tire size. This will be under a heading such as “Specifications,” “Tire Size,” or “Wheels and Tires.”

However, if you can’t find your bike tire size, then follow the below guide.

The Standard Sizing System

If you look at the old traditional tire sizes, there were several sizing systems for bike tires to the point that each country would have its very own tiring method and sizes. 

The same tires would have various sizes in different nations because each sizing system was unique. Therefore, the same numerals were frequently used for multiple tire sizes.

Traditional sizing procedures measure the tire’s outer diameter and width. The diameter would be measured in inches or millimeters, while the width of the tire would be represented by a second number or code. 

For instance, 700C is a minimum outer tire diameter which indicates that the tire width is 700mm, and thus the letter “C” refers to the tire width on a scale from A to D, with A being very narrow and D being broad.

For this method, you first measure the wheel radius, the width of a bike wheel, and the diameter and combine those measurements. You can easily give them to the salesperson when ordering the tire for your bicycle.

» Read my blog post about: 700c Vs. 26 Inch Bicycle Wheels

The ISO Sizing System

People found many errors in the standard or traditional sizing, hence to address those issues the International Organization for Standardization (ISO) established a universal metric-based tire and rim sizing system. 

This approach is far more exact and trustworthy than the other techniques of measurement.

The method employs two numbers: a two-digit number and a three-digit number. The width in millimeters is shown by the first digit. For tires, the number represents the inflated width, but for rims, the number represents the inner width between the rim flanges. 

The second digit is also in millimeters (mm), indicating the rim’s bead seat diameter. These are the numbers to keep in mind when you want to change your tires. If the number matches, then your tire would fit into the rim of the wheel. 

Take 700 x 20C tire size in the standard tire system, these would be a 20-622 in the ISO size system.

When you’re looking for a tire, make sure that the tire must fit the rim properly and is not excessively thin or broad. When the tire is too thin, the tire is more likely to be damaged by the road. 

Meanwhile, if the tire is too broad, the brake shoes may induce sidewall wear, increasing the danger of losing control.

If you want to measure your bike tire size from this method, you first need to check if your bike wheel was manufactured on the ISO system. ISO has a specific procedure for measuring, it uses millimeters to define bicycle tire size. 

Measuring Bike Tire Size for ISO System: Step by Step 

For the ISO system, you will need a measuring tape with metric units (mm) and even if you do not have the mm tape you can easily convert inches to millimeters by multiplying the number of inches by 25.4.

  • Start by making the bike stand in an upright position with the help of a wall or kickstand. 
  • Now measure the diameter, by placing one end of the tape on the wheel center and the other one on the tire’s inner edge and multiply the figure by two. 
  • For tire width, you should employ the same technique as before, place tape on one end of the tire and then measure to the other end. 
  • Do keep in mind that you can use different widths for the same bike as long as the difference is not too huge, and the control remains the same.

How To Measure A Bike Tire Size — Step By Step

To help you measure your bike tire at home, here is a detailed step-by-step guide:

Step #1: Secure the Wheel

Make sure that your bike is in a stable position for you to work and then secure the wheel so you can take its measurements. 

You can use a kickstand to support the bike, or you can simply lean it against a wall or put it upside down. This will help you focus on the given task instead of constantly holding your bike in an upwards position.

Step #2: Measure the Diameter 

To calculate the diameter, you first need to measure the wheel radius which is the distance from the center of the wheel to the edge of the tire. Measure this distance by using a measuring tape. Now multiply the measurement by 2 to get the wheel diameter. 

The most common tire size is the full-inch increment for the diameter. If your measurement is slightly more or less than a full inch, round it up or down to the nearest inch.

Write this measurement on a piece of paper and move toward the next step. 

To calculate the circumference of your tire, multiply the diameter of your tire by 3.14.

Step #3: Measure the Width

After that, you need to measure the tire width. The width is the distance between the flat part of the tire’s tread from one side of the tire to the other. 

To measure the width of the bike’s tire, place the end of the measuring tape at one side of the tire’s tread and measure to the other side. Record that measurement on a piece of paper. 

Keep in mind that standard width measurements are in inches, whereas the ISO method is in millimeters.

» You can also read my post: 10 Possible Reasons Your Bike Tire Keeps Going Flat

Step #4: Combine Those Measurements 

Now that you have successfully recorded the measurements of the diameter and the width, the final step is to combine the measurements to determine your tire size. 

In standard sizing, the diameter comes first, followed by the width. Whereas in the ISO system, the width comes first, followed by the diameter. 

Standard Bike Tire Sizes Explained

The bike tire sizes are dictated by the wheel itself, so the sizes below and their performance features are driven mostly by the wheel diameter. 

However, choosing between factors like the tire’s width, tread, and construction also impacts your riding performance. 

Here are some standard bike tire sizes explained.

1. 700C Bike Tires

If you are a bicycle enthusiast, you must be familiar with the 700C size tires since 700C is the most popular wheel/tire size for standard road bikes. However, commuting and gravel bikes also use this tire size a lot. 

700C tires with a narrow width offer a smooth tread, increasing the speed on pavement. Meanwhile, 700C tires with wide widths offer better control and grip on rough terrains. 

2. 29-Inch Bike Tires

29-inch tires are the largest tire size available for mountain bikes. This size is ideal for increased speed and improved rollover capacity for mountain routes. 

This tire size has gained popularity for mountain riders, however, some shorter riders tend to find them unwieldy.

3. 27.5-Inch Bike Tires

27.5-inch bike tire size is also a widespread size for modern mountain bike tires. They are much more nimble as compared to the 29-inch tires, but some riders are more focused on agility over top speed. 

4. 650B Bike Tires

650B tire sizes are mostly found on gravel or touring bikes. 

650B bike tires have the same inner diameter as the 27.5-inch mountain bike tires. However, the 650B tires are much more geared for the all-terrain, gravel, and adventurous type of riding instead of normal trails. Therefore, they both have separate names. 

5. 26-Inch Bike Tires

26-inch bike tires used to be seen on almost all adult mountain bikes; however, they have been replaced by the 29-inch tire size. Now they are mostly used on teen mountain bikes or old traditional models in the market.

» This could also be something for you: How Much is a New Bike Tire

What Is the Most Common Wheel Size?

The most common tire sizes on a standard road and gravel bike are 700C and 650B and the adult mountain bike tire sizes are 27.5 inches and 29 inches. The most common wheel size for a road bike is 700C which has been the standard size for a couple of years. If you take mountain bike wheel sizes, their common sizes are 26-inch/559 wheels, 27.5-inch/650B wheels, and 29-inch/622 wheels.

The 700 in road bikes refers to the bicycle’s wheel diameter being 700 mm, whereas the ‘C’ refers to the width of the tires. 

The most common and preferred sizes for mountain bikes are 27.5-inch/650B wheels and 29-inch/622 wheels.

The smallest size is the 26-inch which was once considered the standard size for mountain bike wheels. 

However, despite their popularity, the 26-inch size is no longer the standard size, since the large wheel sizes have improved grip, traction, and durability. 

Both 27.5-inch and 29-inch size wheels are more popular now for mountain bikes since they offer a smoother ride. 

Does Bike Tire Width Matter?

If you look at a bicycle, you will notice that the tires are the only components that make contact with the ground surface, which is why the tire width is a crucial element for improved traction and speed of the bicycle. 

If the tires are wide, more rubber would be touching the ground making the bike more stable and comfortable on rough surfaces.

This is why mountain bikes or fat tires bikes have tires that are relatively wider so they can get enough surface area to improve their grip on tricky terrains. 

Wide tires offer the riders a certain control and safety when they are traveling through dirt trials, snowy terrains, or muddy mountain routes. 

Counter to this, road bikes tend to have much narrower tires to reduce friction with the ground. This is because the city roads are smooth and hard surfaces, unlike mountain terrains.

This is why road bike tires are lightweight and more aerodynamic. 

» I have also written this post, about: Studded Bicycle Tires

Final Thoughts on Bike Tire Sizes

Now that you know how to measure a bike tire and how the different sizing systems work, you must be able to easily measure your bike tire size and get a new one without having to worry about getting the wrong tires for your bicycle. 

Overall, understanding the size differences isn’t that hard. Understanding the thorough procedure was essential since if the need ever arises you can eventually help yourself, instead of getting a professional bike expert to help you. 

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