Bicycle Tire Sizes

Bicycle tire sizes can be difficult to understand as there are so many numbers and jargon used. But once you comprehend the basic facts and figures, you won’t have any difficulty buying a new set of tires.


This can be found on the sidewall. The measurement is expressed by two numbers with an X in between (for instance, 700X23). The first number is the diameter and the second number is the width. The diameter (in this case 700) is in mm. Sometimes the size is expressed in inches.

Most bicycles for adults come in the 26 inch or 700 mm bicycle tire size. Most of the 26 inch tires are found on mountain bikes. The 700 measurement is found on most road bikes. The mm size is used widely in Europe, while the inch is employed in the United States.


Using the same example, the width in this case is 23 mm. The greater the width, the greater the tire’s surface contact on the ground will be. The greater the surface contact, the more uncomfortable the ride will be. For this reason, you should get tires with less surface contact.

Decimals and Fractions

Bicycle tire sizes with inch measurements will have decimals on the width, for example, 26X1.75. Sometimes fractions are used like 26X1 ¾. Even if both tires are 26 inches, the different decimal and fraction numbers indicate they are different tires. Do not buy one fraction tire and decimal tire. The tires need to be the same kind.

The ISO Tire Sizing System

Because tire companies use different sizing systems, it can be difficult to get the tire size right. However, the ISO (International Organization for Standardization) has set up tire sizing system to regulate the figures.

Many new bike tires list the ISO figures, width first followed by the diameter. If you need a precise match to replace a tire, match the ISO.

Compatibility Issues

If you want to get new tires, always get the same diameter. However you can select a different width. Most bike rims can work with various widths. However, not all tires have expansive width compatibility. You will have to check the bike manual to be sure.

Sizing Inaccuracies

Buyers need to buy tires from reputable companies because sometimes the sizes are not stated honestly. If you measure the tire size, you will notice that some tires are not as wide as stated. Some manufacturers would also market 700-23 as 700-25 to give them an advantage.

However, the trend these days is towards a standardization of the size. This will make it easier for buyers to buy the right tires. During the early years of bicycle tire manufacturing, nations would make tires according to their own system. This meant the same tire would have different measurements in different countries.

Although there is still some confusion, choosing the right bicycle tire size is easier now than it was before. As long as you pick the right diameter for your bike, the new tires should fit right.

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