Article series: What do the numbers on the bicycle tire mean?

ETRTO size of a bicycle tire

Last updated: 2023-08-11

ETRTO size on a tire label

ETRTO meaning explained with an example

The example tire above has the ETRTO size 42-622.

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.

The number 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.

Note on buying tires

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.

What is ETRTO?

The ETRTO size of a tire is a standardized size specification. It was defined by the European Tyre and Rim Technical Organisation (ETRTO).

What do the other indications on the bicycle tire mean?

This article is part of a series of articles. For the other information on the bicycle tire see:

  1. ETRTO size of a bicycle tire (this article)
  2. Tire inch size and English designation
  3. Tire French size
  4. Bike tread specification