Bike Tire Sizes Explained

Where can you find your bike tire size?

Finding your bike tire sizes is quite easy since they are generally displayed on the tire sidewall.

But what may be more confusing for some is what these tire sizes correspond to, as they can be expressed in three different ways: ETRTO, imperial or metric measurements. Let us shed some light on each of them.

Understanding bike tire sizes

Look for the numbers appearing on the tire wall. You may need to spin the wheel round until you can see them, but they should still be quite easy to spot.
Your bike tire size will probably be given in one of these three ways:

ETRTO bicycle tire size measurements

ETRTO bicycle tire sizes appear as two digits separated by a dash: For example, 23-622, 25-622 or 28-622. The bike tire size meaning is deciphered as follows:

23-622 / 25-622 / 47-622

The first digit is the tire's width in millimetres at a given pressure and rim width. So, for instance, a typical road bike tire size would display a smaller first pair of digits than a mountain bike (see mountain bike tire sizes explained). Michelin follows the ETRTO recommendations.

23-622 / 25-622 / 47-622

For now, it’s important to understand that the second, three-digit number of an ETRTO bicycle tire code relates to the rim ‘s seat diameter – again expressed in millimetres.

Keep in mind that the ETRTO measurement is the least used regarding the choice of your bicycle tire.

Imperial bicycle tire size measurement

Some cyclists are more familiar with the imperial measurement. It is shown as a sequence of numbers like for example: 29 x 2.10 or 29 x 2.25. This type of measurement is usually used for mountain bike & city tires.

29 x 2.10 or 29 x 2.25

Here, the bike tire sizes are given in inches. The first number states the overall diameter (including the tire) at a given pressure and rim width. The term 29 inches is often used to define the rim’s seat diameter. But that’s not the case, 29 inches is the overall diameter including the tire.

29 x 2.10 or 29 x 2.25

The second number gives the width of the tire mounted on the rim. So, in the examples above, 2.10 represents two-and-a-tenth inches, while 2.25 represents two-and-a-quarter inches at a given pressure and rim width.

Imperial bicycle tire sizes sometimes have three numbers:

22 x 1 3/8 x 1 1/4

When this happens, the first number always corresponds to the overall diameter in inches. Then, the second number give the tire height and the final number represents the tire's width. So, in the example given, the tire would have a diameter of 22 inches, a height of one-and-three-eighths of an inch, and a width of one-and-a-quarter inches. That's why using Michelin's bike tire size guide for cyclists can be very helpful for understanding bicycle tire sizes

Metric bicycle tire size measurements

Last but not least, cyclists will often encounter tires with markings such as 700 x 23C or as 700 x 28B, for example. This sizes, which are in millimetres, are often used for road tires measurement.

700 x 23C or as 700 x 28B

Here, the first number is the overall diameter of the tire at a given pressure and rim width.

700 x 23C or as 700 x 28B

The second part indicates the tire's width in millimetres, plus the rim size expressed by a letter code.

Do you find all this complicated? Don’t worry! Since you can find different type of measurements for the same tire, Michelin provides a bike size chart to help you convert one measurement to another, as we will explain below.

Bike tire size chart: How to convert a measurement?

In our bike tire size chart, there are 3 columns, one for each measurement, which makes it easy to convert bike tires sizes from metric to imperial / or vice versa. You can also use the bike tire size chart to convert ETRTO (European Tire and Rim Technical Organisation) bicycle tire size data to one of the other types.This way you will find the correspondence between the measurement indicated on your tire and that indicated for the tire you wish to buy.

Bicycle tires for different types of bikes

Bike tire size chart

Click below to see our Bize tire size chart pdf.

View chart

Typical Road bikes

For road bikes, bike tire sizes are generally expressed in metric measurements. Although road bicycle tire sizes can be expressed using the other systems, products like Michelin road racing tires are always listed with their 700mm diameter appearing first. This is also standard practice for racing tires, cyclocross tires, everyday road bike tires, training tires as well as road bike tires designed for harsher terrains – such as Michelin gravel tire.

Typical MTBs and city bicycles

However, it’s not the same for mountain bikes. An MTB tire will typically display primary tire dimensions in inches (Imperial measurement). This is the same for city bikes, a bicycle class which also includes trekking bikes as well as children's bicycles.

ETRTO is a common standard

ETRTO is a useful multi-purpose system designed to work well for all types of bicycles. So, anything from a child’s first bicycle to a professional road bike will have tire listings that use this system. But as said before, this type of measurement is the least used.

Can I change the tire size on my bike?

Perhaps you are wondering whether you can change bicycle tire sizes to suit different situations? It is sometimes possible to use different bike tire sizes, provided the difference in size is only negligible. For example, some MTB riders choose slightly wider tires on certain terrains.

However, the dimensions of your wheel rim will obviously remain the same, so it is usually best to stick to the recommended bike tire size. Otherwise your bike’s performance could be severely impaired, which could even interfere with the operation of the brakes. Your bike tire size depends on your bike specifications. So if you want to change your tire size, Michelin advises you to contact a certified professional or your bike manufacturer.

Bike Tire Sizes explained: our complete guide