Last updated: 2022-05-15
The example tire above has the ETRTO size
Here, the number
42 means that the tire is approx. 42 mm (i.e. 4.2 cm) wide when inflated. The tyre width is measured at the widest point of the tire.
622 behind it means that the tire has an inner diameter of 622 mm (i.e. 62.2 cm). The inner tire diameter is measured at the tire bead that rests on the rim. Therefore, this size is identical to the nominal rim diameter.
The ETRTO specification on the tire is, in my opinion, the most important information when buying a new tire or tube to fit the existing rim. Simply enter the details on your tire on the respective page and the corresponding sizes will be displayed.
The background is that the ETRTO specification is standardized and supported by all tire manufacturers. In addition, it is the most accurate size indication on the tire, more precise than the inch size and the French size.
The ETRTO size of a tire is a standardized size specification. It was defined by the European Tyre and Rim Technical Organisation (ETRTO).
This article is part of a series of articles. For the other information on the bicycle tire see: