When choosing the right bicycle tire, the size is crucial. There are four common systems: the inch size, the German size system, the French size system and the ETRTO size system. The first 3 systems are somewhat outdated, which is why they have created a general size system, the ETRTO system.
* You can find the size on the side of the bicycle tire. In some cases there are several sizes listed. In this case, it is easiest to find the ETRO size. You can recognize this by the following structure: two digits, then a dash, and then again three digits (for example, 51-559).
In this blog, we will delve deeper into the different size systems. This way, you’ll know which size to buy.
1. Inch size
The inch measurement is the oldest system and has been used since the invention of the bicycle. It includes three aspects: diameter, height and width. For example, the measurement is 28 x 1 5/8 x 1 1/8:
- The first digit (28) indicates the diameter of the bicycle tire.
- The second number (1 5/8) represents the height of the band.
- The third digit (1 1/8) stands for the width of the tire.
Keep in mind that one inch is approximately 2.54 centimeters, which means that the diameter of the bicycle tire in this example is approximately 71 centimeters.
2. German system of measurement
The German measurement system is similar to the inch system, but the height and width have been reversed. For example, the inch measurement 28 x 1 5/8 x 1 1/8 is in the German system 28 x 1 1/8 x 1 5/8. In this case, the first digit (28) still represents the diameter of the tire, the second digit (1 1/8) represents the width, and the third digit (1 5/8) represents the height.
3. French system of measurement
The French sizing system uses millimeters for the tire size, specifying only the diameter and width. For example, the inch size 28 x 1 5/8 x 1 1/8 is in the French system 700 x 28C. Please note that French sizes are rounded, which can sometimes lead to confusion.
4. ETRTO size
The ETRTO sizing system is designed to reduce confusion between the different systems. The designation is in millimeters, for example 28-622:
- The first number (28) is the width of the tire.
- The second number (622) is the diameter of the wire seat of the rim (This is the place where the tire is attached to the rim).
The ETRTO system is the system currently adhered to by manufacturers. It is often prominently displayed on the tire, but older systems may still be mentioned in parentheses.
