How to Measure Tires And Tubes Size For Bicycle

The size of the bicycle tire and its compatible tube is a long development of the most confusing ideas. With now 200 years of history of the bicycle, no less than 200 different sizes for tires have been introduced. How to look through them? We give you tips on the right tire size. And which tire is compatible with which rim and tube.

But first, we must agree on the most important terms. A tire is not the same as a tube. And diameter is not the same as size. At least for this post here, we have drawn and defined the following lines.

tire and rim width

a: Tire width;     b: Rim diameter/ Tire size;     c: Tire diameter

The Two Most Important Terms

Tire Width (a): The diameter of the tire in cross-section, in the bicycle industry it is common to consider the tire round in cross-section as in a cylinder. Although this cross-section is never perfectly round due to the structure of the tire and rim. Moreover, this diameter is minimally modified by the internal width of the rim (jaw width).

Tire Size (b): Corresponds to the rim diameter (diameter without sidewall). The inner diameter of the tire is measured as it is mounted all around. It does not mean the total size of the mounted and inflated tire (c)!

There are many more relevant sizes and ratios, we present them in detail below. For the tube and tire sizing, however, these two defined values are decisive.

Properly Select Bicycle Tube Size

A bicycle inner tube stretches a lot! Therefore, a tube always fits a large number of tire sizes. It stretches in circumference and width. Means: A tube for 26″, 27.5″ or 28er tires can fit well on all three tires, eg the Schwalbe 19 tube.

On the bicycle inner tubes, the size specification has been established according to ETRTO. This looks like this: 28-622. The first two numbers are the tire width and the last three the tire size (corresponds to rim size). So check your tire (casing) what specification it has (or an old tube you want to replace). You will always find the notation from xx-yyy.

You also have to choose the right valve for the wheel! If you are unsure, here is a valve lesson: Bicycle tube valves.

  • Finding The Right Tube:

    Bicycle tubes are very stretchy and one tube size usually covers many tire sizes. But to be on the safe side, it would always be advisable to order suitable hoses directly when changing sizes. Here we have programmed a hose size finder that you can use to easily find the right hose for a given size:
    hose size calculator

Choose The Right Bike Tire Size

Looking for the right tire? Then you have to pay attention to the following points. So that the new tire fits perfectly. More on the theory and details can be found further in the text.

  • Tires And Rims Have To Fit Together:

    Here one speaks colloquially of 26, 27.5, and 28 tires. This means tire sizes in inches. However, these inch sizes are not to be taken exactly, they are pure thumb sizes. But all three have clear diameters between rim and tire!

    • 26″ = 26 = 559mm Rim Diameter

      If you have a wheel with 26 tires, the rim has a diameter of 559mm. Your tire must end in xx-559, e.g. 38-559 (according to ETRTO notation).

    • 650B = 27.5″ = 584mm Rim Diameter

      The intermediate size “650B” or 27.5 is a common size on MTB and French randonneur touring bikes. But they are also becoming fashionable for gravel bikes. For these tires, the ETRTO designation must end with xx-584, e.g. 38-584 (after ETRTO notation).

    • 28er = 28″ = 29″ = 622mm Rim Diameter

      The standard tire for most bikes in Europe. Also known as a 28 tire (or 28-inch tire). Here the tire size must end in 622 according to ETRTO notation, e.g. 32-622.
      The 29er tires (29″) are just a marketing term! These tires fit the same rims as 28 tires and are just “Big 28s”. More on this in a separate chapter below.

  • Tire Size Must Fit The Rim Width:

Not only the diameter of the rim is critical. Also, a rim with an inside diameter of 21mm can only accommodate tires of a certain size. The narrower the rim, the smaller the compatible tires. MTB rims have wider rims and road bikes are correspondingly narrower. More details can be found in the chapter below including a table of compatible sizes!

  • A Tire Must Fit Into The Frame:

Your bike can only accommodate certain tire sizes. Otherwise, the tire will rub against the frame or fork. Even if the clearance is too small, then in the worst case this can lead to an unintended emergency braking. If a stone gets between the tire and bike frame and wedges. Which tires fit your bike frame can only answer the manufacturer! Otherwise, only “try over study” helps.

  • Order Matching Tube To The Tire:

Remember, if you change your tire size, you may need a smaller or larger tube in the new tire.

ETRTO – Tube And Tire Size Standard Notation

ETRTO now specifies the most widespread standard in Europe. You can find this information on every purchasable tire and tube in Germany. Old and alternative designations are the French and English designations. You can also find these on most tires and tubes.

Tip: ETRTO is your friend. Finds the size specification with two numbers, dash, and three numbers. This is the most reliable information to find the right tire.

Tube And Tire Size Standard NotationETRTO Overview of English tire size notation.

Confusing with the English spelling is that the specification is “28”, but does not mean that the tire must have such an outer diameter. Here one speaks rather of a thumb or guideline size, if the tire sits and runs round he has about a complete outer diameter of 28″. This is conceivably inaccurate. This rather sets the standard of the rim this tire meets. Factually, however, these size specifications are not correct.

After all, the decisive factor for the tire is that it fits on the rim. Whether he then has a certain size (outer diameter) or not is only a question of the bicycle frame (do I get the total outer dimension in the frame at all?). Between tires, brakes and frame are usually but enough buffer planned. It only gets tight with road bikes and similar relatives (gravel, allroad, and randonneur bikes).

The surveyors of bicycle tires were not impressed by the imprecise specifications. Thus, the English and French size specification always indicates the outer diameter, but without being mandatory. No wonder this had to be improved.

Tips About The Bike Tire Size

Here you can find more detailed tips on tire size and choosing the right one for you.

Tips For Finding The Right Tires Quickly And Easily

So that you don’t lose a lot of time, here are a few tips on how to find the right tire as quickly as possible.

1. Buy The Same Tire Again

Sounds banal, but that is pragmatic and proven. Look for something like this on your current tire: 43-622 (two-digit number + hyphen + three-digit number). This is the tire width (two digits) and size (three digits). Type this size into Google, go to your bike retailer or Amazon or… and you’re on the safe side.

2. Do You Want To Upgrade Your Tires?

It should be smaller or larger, but you don’t know how much more or less is even possible? It’s difficult to give a general answer! It then depends on your bike (see tips above), the rim size, and the internal width of the rim. As a rule, however, you can always put on +/- 5mm larger or smaller tires. So if the current tire measures 43-622, then 38-622 or 48-622 are also no problem. With racing bikes, however, the tolerances are significantly lower!
To be on the safe side, consult your local dealer or workshop.

We have dedicated an entire chapter below to the topic of tire upgrades.

But before that, let’s talk about the basics and sizing. Which we have named several times but have not yet defined more precisely.

The Main Tire Sizes

imp tire size

Instead of boring you with an oversized table of possible sizes, here is a brief outline of the relevant sizes. 28″ (inch) tires are particularly common on bicycles for adults . There are 26″ bikes for youngsters. Small children with balance bikes, prams, carts, etc. have smaller wheels – but we will hide these for now.

tire and rim cross-section

Tire and rim in cross-section.
a: tire width when inflated;
b: Inner rim width between the rim claws (rim inner width);
c: diameter from rim well to rim well; Also rim diameter, rim size; Identical to tire size (see definition at the beginning of the article)
d: overall diameter of the tire

As you can see, you can measure different points and arrive at different sizes for the same tires. This also explains why different size specifications are in circulation. According to ETRTO (c) and (a) is measured, for example, specification 28-622 means 622mm rim size, and 28 is the width of the tire. This also allows you to determine the approximate total outside diameter (622+28 = 650mm total tire diameter). Tires with the size indication 622 correspond to the rim size 28 inches.

Depending on how you put on the tape measure, you come to the three size specifications according to ETRTO, EN, or FR.

Which Tire Fits Which Rim On The Bike?

That was quite a lot of basic technical information – but which tire do you need now? The decisive factor is that the rim size is correct. This is indicated differently, depending on the size specification. For ETRTO specifications such as 37-622, the second combination of numbers indicates the rim size (after the hyphen). In this case, it is therefore 622mm rims – commonly referred to as 28-inch rims.

Accordingly, you need 37-622 tires again, or you can also take 32-622 or 40-622 tires – depending on whether you want thinner or thicker tires. In the English specification, such as 28×1.5, the first number indicates the diameter. Where the entire tire diameter with tire and rim is meant (but accordingly misleading).

But beware – not all tires fit all rims. Following the ETRTO standard, there are recommendations on which tire width is compatible with which rim inner diameter. Narrow tires should be on narrow rims and large MTB tires on correspondingly wider rims. So that the tire does not collapse in the curve (rim too narrow) or jump off the rim (tire too wide). The recommendation of the ETRTO are as follows:

range

The ETRTO standard gives a relatively narrow scope for rim and tire combinations. However, most tire and rim manufacturers are expanding this range.

The tolerance range is very small, especially with narrow racing bike rims (14mm for vintage racing bikes, or 15 to 16mm for more modern racing bikes). Only really narrow tires fit on it. From 17mm, however, the recommendation jumps up to normal trekking tires or even MTB tire sizes. So you have a lot of choice and leeway.

However, Schwalbe, Continental, and other tire manufacturers, as well as rim manufacturers such as Mavic, usually extend the ETRTO recommendation. You can follow their assessment accordingly and also combine other inner rim widths and tire widths. It is worth researching the manufacturer before buying. In most cases, the ETRTO table does not have the last word!

Bike Tire Size Chart

 

Between these sizes, there are always intermediate sizes. These are then, for example, 22 – 622. The first number is the width. So you can quickly get an idea of ​​what the tire looks like.

Tire Upgrades – What Is Possible? 26″ To 28″? What Is Important?

Is it generally possible to change the size of the tire on the bike? So instead of switching from 26 inches to 28 inches?
Yes, this is possible in some cases. But it depends on the following points.

  • Brakes:

    Your bike must be equipped with disc brakes. Already standard on most bicycles today. Rim brakes, on the other hand, are always set to exactly one tire size. So if you have classic brakes that grip the rim, then other rim and tire sizes will not be an option. However, you can still change the tire width, see the chapter above on combinations of rims and tires.

  • Frame And Fork:

    There must be adequate clearance between the tires and the frame and fork. The new tire must fit between the chainstays and must not touch the seat tube on the frame. The fork must also offer plenty of space so that the new tire can pass with sufficient clearance.

Examples Of Common Tire Sizes

Here are a few examples to give you an idea. How big the theoretical sizes look like in reality.

Bicycle Tires 32-622 // 28 Inches

bicycle tire size32-622 tires from Continental on the classic steel racing bike. This size is the maximum that can still be ridden on a racing bike without touching the brake caliper or frame. That little clearance is borderline as something could easily get wedged between the tire and fork/brake. And would lead to a fall.

Bicycle Tires 37-622 // 28 Inches

bicycle tire size 2.0

Why Are There 28″ And 29″ Inch Tires?

Thanks to marketing. The 29-inch bicycle tire is an invention of marketing. The actual size of the tire varies, while the rim is always the same size. The outer diameter of a narrow 23mm tire (e.g. 23 – 622 on a road bike) is only 26″. Nevertheless, we refer to all adult bikes in Europe as 28″ bikes.

The 29″ is achieved with extra-large mountain bike tires. To get to the actual 28″ one would have to ride tires of size 40 – 622. Because if you convert the 622mm into inches, you’ll notice: The rims are not 28 inches at all, but between 24 and 25 inches. It has simply become customary that one speaks of the (approximate) total size of the wheel when talking about 28-inch rims.

Tube Sizes

A bicycle tube must always be selected to fit the tire width and size. As a rule, the tube manufacturer always indicates with which sizes a tube is compatible. Thus, you can simply take the common tables and check whether the tube is compatible with your tire.

tubing sizeA bicycle tube always fits many different sizes because it is flexible. Therefore, the tube manufacturer always provides a list of compatible tires.

In addition to the tire size, you also have to consider the shape and size of the bicycle tube valve for the tube. The valve must match your rim. The easiest way is to look at the current valve on your tire. Take the valve to the bike shop and ask for a tube with the same valve.

tube valveWhen it comes to the valve, it depends on the design (Dunlop, Sclaverant, or Schrader Auto valve). All three have different diameters. And depending on your rim, a valve will fit or not.

valve fitting

With the Sclaverant valves, the height of the rim is also important. Lightweight rims often have a high rim flange. Then you need an extra-long Presta valve for your racing bike.

Avoid Buying The New Bicycle Tube

Buying a new bicycle inner tube can also be avoided. Every cycling enthusiast knows that repairing a tube is not difficult – a bicycle tube can be used for years without having to invest in new tubes.

FAQs

What does ETRTO Mean?

ETRTO stands for the European Tyre and Rim Technical Organisation. Their standard is now the most widely used in Europe as far as tire sizing is concerned. What needed improvement about the other standards that existed before it was that they specified the outer diameter of the tires, but this depended on the thickness of the tire. ETRTO, on the other hand, uses the rim size as the size indicator – that is, the actual measurement when it comes to whether or not a tire will fit on a wheel.

Bicycle Tires: What do the Numbers Mean?

The size numbers – depending on the measurement – have a specific meaning that relates to the tire’s size dimensions. Our graphic under ETRTO explains this in more detail. If you get a new bicycle tube, it should have the same size information!

Bicycle Tire: Where does it say the Size?

On a bicycle tire, the size should be indicated somewhere on the side in different size specifications. A specification like 40-622 (two numbers separated by a hyphen) refers to ETRTO. Most often you can also find the inch designation, which looks something like 28×1.50. The ETRTO size specification is usually enough to find a suitable tube – this should have the same ETRTO specification.

Jonathan Tim
Jonathan Tim
A bicycle geek since early childhood spent his twenties as a mechanic in bike shops. His passions include flatland BMX, unicycles, cycle touring, mountain biking, and road riding.