Bicycle Tires and Inner Tube Sizes

The size of the bicycle tire and thus compatible inner tube has a bright history 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 are you supposed to see through that? I’ll give you tips on the right tire size. And which tire is compatible with which rim and tire.

But first we need to check in on the two most important terms. Tire is not equal to inner tube. And diameter does not equal size. At least for this post here, we have drawn and defined the following lines.

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 combined structure of the tire and rim. And besides, this diameter is minimally changed by the inner width of the rim.

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 is not describing the total size of the mounted and inflated tire (c)!

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

Properly select bicycle inner tube size

A bicycle inner tube stretches a lot! Therefore, one 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 according to ETRTO has become established. This looks like this: 28-622. The first two digits are the tire width and the last three are the tire size (corresponds to rim size or rim diameter). So check your tire (casing) what specification it has (or an old tube you want to replace). You will always find the notation of two digits followed by dash and another three digits: xx-yyy.

In addition, you must choose the right valve for the wheel! If you’re unsure, here’s a valve guide: bicycle tube valves.

• Find suitable inner tubes:
  Bicycle inner tubes are very stretchy and one tube size usually covers many tire sizes. But it would always be recommended for safety in case of size changes also to order directly matching inner tubes. Here we have programmed an inner tubes size tool, with which you can easily find the right product for a given tire-size:
  Inner Tube Size Tool

Correctly select bicycle tire size

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

• Tire and rim must fit together:
  In this article I’ll stick to the terms 26, 27.5 and 28 tires. This refers to tire sizes in inches. However, these inch sizes are not to be taken exactly but pure rule of thumb sizes. As all three have specific diameters that match rim and tire!
  • 26″ = 26er = 559mm rim diameter
    If you have a wheel with 26 tires, then the rim has a diameter of 559mm. Your tire must end as xx-559, eg. 38-559 (according to ETRTO notation).
  • 650B = 27.5″ = 584mm rim diameter
    The intermediate “650B” or 27.5 size is a common size on MTB and French randonneur touring bikes. Come with Gravel bikes again in fashion. For these tires, the ETRTO designation must end in xx-584, e.g. 38-584 (according to ETRTO notation).
  • 28er = 28″ = 29″ = 622mm rim diameter
    The standard tire for most bikes in Europe. Also known as 28 tires (or 28 inch tires). Here the tire size according to ETRTO notation must end on 622, so eg. 32-622.
    The 29er tires (29″) are just a marketing term! These tires fit on the same rims as 28er tires and are in principle simply “Big 28er”. More on this below in its own chapter.
• 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 rim inner bead sizes and road bikes correspondingly narrower. More details can be found in the chapter below including a table of compatible sizes!
• Tire must fit the frame:
  Your bike can only accommodate certain tire sizes. Otherwise the tire will rub against the frame or fork. Also, if the margin is too small, then in the worst case this can lead to an unintended “emergency” stop, throwing you off the bike. When a stone gets between the tire and the bicycle frame and wedges. Which tires fit your bike frame can only answer the manufacturer! Otherwise, the only thing that helps is “try before you buy”.
• Order matching inner 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 sets the most common standard in Europe. You will find this information on every purchasable tire and inner tube in Germany. And mostly for the rest of the world, too. Old and alternative names are the French and English notations. You will also find these on most tires and tubes.

Tip: ETRTO is your friend. Searches the size specification with two digits, dash and three digits. This is the most reliable indication to find the right tire.

What’s confusing about the “English” notatoin is that although it says “28”, it doesn’t mean that the tire actually has to have that kind of outer diameter. Here it is just a rule of thumb or guideline, if the tire sits and runs round it has approximately a complete outer diameter of 28″. This is conceivably inaccurate. This rather sets the standard of the rim that meets this tire. In fact, however, these size specifications are not correct.

After all, the decisive factor for the tire is that it fits on the rim. Whether it then has a certain size (outer diameter) or not is only a question of the bicycle frame (can we get the total outer dimension into the frame in the first place?). However, there is usually enough buffer between tires, brakes and frame. It only gets tight with road bikes and closely related bikes (gravel, allroad and randonneur bikes).

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

All tips about the bike tire

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

Tips to quickly and easily find suitable tires

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 this is pragmatic and proven. Look for an indication on your current tire that looks something like this: 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 dealer or Amazon or or… and you are on the safe side.
2. You want to upgrade your tire?
   You want it to be smaller or bigger, but you don’t know how much more or less is even possible? That’s hard to give a generic answer to! It then depends on your bike (see tips above), the rim size and rim width. As a rule, however, you can always fit +/- 5mm larger or smaller tires. So if the current tire measures 43-622, then 38-622 or 48-622 are also no problem. With road bikes, however, the tolerances are much lower!
   To be on the safe side, consult your local dealer or workshop.

We have devoted an entire chapter to the subject of tire upgrades below.

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

The main tire sizes

Instead of boring you with an oversized table of possible sizes here is a short outline of the relevant sizes. Most common are 28” (inch) tires on adult bicycles. For teenagers there are 26” wheels. Toddlers with wheels, strollers, carts, etc. have smaller wheels – but we’ll ignore those for now.

As you can see, you can measure different intersections and come up with different sizes for the same tires. This also explains why a wide variety of sizes are in circulation. According to ETRTO (c) and (a) is measured, for example, the 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+(2×28) = 678mm total tire diameter). Tires with the size indication 622 correspond to the rim size 28 inches.

So depending on how you put on the tape measure, you come to the three sizes 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 crucial thing 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 digits indicates the rim size (after the dash). So in this case, we’re talking about 622mm rims – commonly referred to as 28-inch tire rims.

Accordingly, you need 37-622 tires again or 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 total tire diameter is meant with tire and rim (but accordingly misleading).

But be careful – not all tires fit all rims. Following the ETRTO standard, there are recommendations 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:

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

Schwalbe, Continental and other tire manufacturers as well as rim manufacturers such as Mavic usually extend the ETRTO recommendation, however. You can follow their assessment accordingly and also combine other rim inner widths and tire widths. It is worthwhile to research the manufacturer before buying. The ETRTO table does not have the last word in most cases! The tire and rim manufacturer will set the maximum sizes.

Examples of tire-rim combinations of individual manufacturers:

• Schwalbe: https://www.schwalbe.com/de/reifenmasse
• Continental: https://blobs.continental-tires.com/www8/servlet/blob/245972/82ac135ad2ef00bc46c0a163aa91a710/warning-notice-data.pdf

Bicycle Tire Size Table

ETRTO-Größe	EN-Größe	FR-Größe	Felgengröße in Zoll	Einsatz / Körpergröße
20-622	28x3/4	700x20C	28	sehr schmale Rennradreifen
28-622	28x1 5/8x1 1/8	700x28c	28	schmale Rennradreifen
32-622	28x1 1/4x1 3/4	700x32c	28	sportliche Tourenräder
37-622	28x1 5/8x1 3/8	700x37c	28	Trekkingrad
40-622	28x1,5	700x40c	28	Trekking- und Tourenrad
42-622	28x1,6	700x42c	28	schmale MTB-Reifen
47-622	28x1,75	700x47c	28	MTB-Reifen
40-406	20x1,5	--	20	sportliches Kinderrad / 115cm - 130cm
50-406	20x2,0	--	20	Kinderrad MTB / 115cm - 130cm
40-507	24x1,5	--	24	sportliches Kinderrad / 125cm - 145cm
50-507	24x2,0	--	24	Kinderrad MTB / 125cm - 145cm
44-559	26x1,75	--	26	Jugendfahrrad / 140cm - 165cm
50-559	26x1,95	--	26	Jugendfahrrad MTB / 140cm - 165cm
23-571	26x7/8	650x23c	ca. 26	Tokyobike (japanische Import-Bikes)
54-622	29x2.1	--	28	"29 Zoll" MTB-Reifen

Between these sizes there are always intermediate sizes. These are then e.g. 22 – 622. The first number is the width. So you can quickly get an idea of how the tire looks.

Tire upgrades – What is possible? 26″ to 28″? What does it depend on?

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

• Brakes:
  Your bike must be equipped with disc brakes. Today already standard on most bicycles. Rim brakes, on the other hand, are always fixed to exactly one tire size. So if you have classic brakes that operate on the rims sidewals, then other rim and tire sizes will be out of the question. But you can still change the tire width, see chapter above on combinations of rims and tires.
• Frame and fork:
  There must be sufficient 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 clearance so that the new tire can pass with sufficient distance.

Examples of common tire sizes

Here are a few examples so you can get an idea. How big about the theoretical sizes look in reality.

Bicycle tire 32-622 // 28 inch

Bicycle tire 37-622 // 28 inch

Why are there 28” and 29” inch tires?

Thanks to marketing. In fact, 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. In fact, 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 actual 28” you would have to run tires size 40 – 622. Because if you convert the 622mm in inches, you notice: The rims are not 28 inches at all, but between 24 and 25 inches. It has simply become customary to speak of the (approximate) overall size of the wheel when talking about 28-inch rims, for example.

Inner tube sizes

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

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

In addition to the tire size, however, you must also consider the shape and size of the bicycle tube valve. The valve must fit your rim. The easiest way to do this is to look at your tire’s current valve. Take the valve to the bike store and ask for a tube with the same valve.

With 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.

With the Sclaverant valves, it also depends on the height of the rim. Lightweight rims often have a high rim flange. Then you need an extra long Sclaverand valve for your road bike.

Avoid buying the new bicycle tube

However, the purchase of a new bicycle tube can also be avoided. Every bike enthusiast knows, mending an inner tube is not difficult – so you can use a bicycle tube for years without having to invest in new tubes. We have the instructions:

FAQ