Tube Sizes Demystified !

Tubes, Tubes Everywhere, in all sizes, but I'm confuses so much with the jargons! - This is often the case we hear all the time as tubes is used all around the world and people and companies prefer to call them and denote them in their own language and terminologies! - Here's a guide to understand them better and in detail! 🥸

What do the various size specifications on bicycle tires mean?

Nowadays, bicycle tire sizes are all marked according to ETRTO (European Tire and Rim Technical Organization) standard. However, older English and French tire size dimensions are still used as well.

The ETRTO size specification 37-622 indicates the width of 37 mm and the tire inner diameter of 622 mm. This dimension is clear and allows a precise classification of the rim size.

The inch marking (e.g. 28 x 1.40) states the approximate outer diameter (28 inches) and the tire width (1.40 inches). Another inch marking is 28 x 1 5/8 x 1 3/8 (approximate outer diameter x tire height x tire width); it is also common.

Inch sizes are not precise and lack accuracy. For example, diameters 559 mm (MTB), 571 mm (Triathlon) and 590 mm (Touring) are all classified as 26 inch. Tires with diameters 622 mm and 635 mm are both classified as 28 inch. Oddly enough, tires with an inner diameter of 630 mm are classified as 27 inch.

These classifications originate from the time of tire brakes. In those days, the exact outer diameter of the tire was defined by the brake. Depending on tire width, various standards for the inner diameter applied.

Inch dimensions are widely used in both MTB sport and English language countries. Therefore, we will continue to use these specifications for all tires. But only in decimal form, e.g. 26 x 2.25. Experience tells us that nowadays very few users are familiar with the classical fractional inch dimensions, such as 28 x 1 5/8 x 1 3/8.

When the 29 inch MTB tire size was introduced a few years ago, it had the same inner diameter of 622 mm, known as 28 inch in Europe.

The latest tire size is 27.5 inches. This tire size is favored for MTBs which are too small for the very big 29 inch wheels, in order to benefit from the advantages of bigger diameters. This is the case, for example, with bicycles having a very long suspension travel or very small frame sizes. 27.5 inch tires have an inner diameter of 584 mm and are identical with the old French size marking 650B.

French size markings (e.g. 700 x 35C) give the approximate tire outer diameter (700 mm) and width (35 mm). The letter at the end indicates the inner diameter of the tire. In this case, C stands for 622 mm. French size markings are not used for all tire sizes, so, for example, it is not used for MTB sizes. 

	ETRTO	Inches	French
Size marking	37-622	28 x 1.40 28 x 1 5⁄8 x 1 3⁄8	700 x 35C
Outer diameter	-	ca. 28 inch	ca. 700 mm
Inner diameter	622 mm	-	-
Tire width	ca. 37 mm	ca. 1 3⁄8 inch bzw. 1.40 inch	ca. 35 mm
Tire height	-	ca. 1 5⁄8 inch	-

How many tire sizes are there?

The following list shows all common tire sizes. For virtually every tire size, you should be able to find a corresponding ETRTO-size in this list.

The current Schwalbe sizes and markings are given in bold. We have tried to list in addition all tire sizes which are currently used on the market or which were used in the past. These classical fractional size indications are also often engraved on old Schwalbe tires. Sometimes, you still find them on current models which have already been available for quite a long time.

	ETRTO	Inch	French
12"	47-203	12 x 1.75
		12 x 1.90
		12 ½ x 1.75
		12 ½ x 1.90
	50-203	12 x 2.00
	54-203	12 x 1.95
	57-203	12 ½ x 2 ¼
	62-203	12 ½ x 2 ¼
14"	47-254	14 x 1.75
		14 x 1.90
	50-254	14 x 2.00
	40-279	14 x 1 ½	350 x 38B
	37-288	14 x 1 3⁄8	350 x 35A
		14 x 1 5⁄8 x 1 3⁄8
	40-288	14 x 1 5⁄8	350 x 38A
	44-288	14 x 1 5⁄8 x 1 3⁄8	350 x 42A
	47-288	14 x 1.75
	32-298	14 x 1 ¼	350 x 32A
16"	40-305	16 x 1.50
	47-305	16 x 1.75
		16 x 1.90
	50-305	16 x 2.00
	54-305	16 x 1.95
		16 x 2.00
	57-305	16 x 2.125
	40-330	16 x 1 ½	400 x 38B
	28-340		400 x 30A
	32-340	16 x 1 3⁄8 x 1 1⁄4	400 x 32A
	37-340	16 x 1 3⁄8	400 x 35A
	44-340	16 x 1 5⁄8
	28-349	16 x 1 1⁄8
	30-349	16 x 1.20
	32-349	16 x 1 ¼
		16 x 1.25
	35-349	16 x 1.35
	37-349	16 x 1 3⁄8
17"	32-357	17 x 1 ¼
	32-369	17 x 1 ¼
18"	28-355	18 x 1 1⁄8
	32-355	18 x 1.25
	35-355	18 x 1.35
	40-355	18 x 1.50
	42-355	18 x 1.60
	47-355	18 x 1.75
		18 x 1.90
	50-355	18 x 2.00
	37-387	18 x 1 ½
	28-390	18 x 1 1⁄8	450 x 28A
	37-390	18 x 1 3⁄8	450 x 35A
	55-390		450 x 55A
	57-390		450 x 55A
	37-400	18 x 1 3⁄8
20"	54-400	20 x 2 x 1 ¾
	23-406	20 x 0.90
	25-406	20 x 1.00
	28-406	20 x 1.10
		20 x 1 1⁄8
	32-406	20 x 1.25
	35-406	20 x 1.35
	37-406	20 x 1.40
		20 x 1 3⁄8
	40-406	20 x 1.50
	42-406	20 x 1.60
	44-406	20 x 1.50
	44-406	20 x 1.625
	47-406	20 x 1.75
	47-406	20 x 1.90
	50-406	20 x 2.00
	54-406	20 x 2.10
		20 x 2.00
	55-406	20 x 2.15
	57-406	20 x 2.25
		20 x 2.125
	60-406	20 x 2.35
	54-428	20 x 2.00
	40-432	20 x 1 ½
	37-438	20 x 1 3⁄8
	40-438	20 x 1 3⁄8 x 1 ½
	28-440		500 x 28A
	37-440		500 x 35A
	40-440	20 x 1 ½ NL	500 x 38A
	23-451	20 x 0.90
		20 x 7⁄8
	25-451	20 x 1.00
	28-451	20 x 1 1⁄8
	37-451	20 x 1 3⁄8 B.S.
22"	44-457	22 x 1.75
	44-484	22 x 1 5⁄8 x 1 ½
	25-489	22 x 1.00
	37-489	22 x 1 3⁄8 NL
	40-489	22 x 1 3⁄8 x 1 ½
	50-489	22 x 2.00
	28-490		550 x 28A
	32-490	22 x 1 3⁄8 x 1 1⁄4	550 x 32A
	37-490	22 x 1 3⁄8	550 x 35A
	47-498	22 x 1 3⁄8 x 1 1⁄4
	25-501	22 x 1.00 B.S.
	32-501	22 x 1 ¼
	37-501	22 x 1 3⁄8
24"	40-507	24 x 1.50
	44-507	24 x 1.625
		24 x 1.75
	47-507	24 x 1.75
		24 x 1.85
		24 x 1.90
	50-507	24 x 2.00
		24 x 1.90
		24 x 2.125
	54-507	24 x 2.10
	55-507	24 x 2.15
	57-507	24 x 2.25
		24 x 2.125
	60-507	24 x 2.35
	62-507	24 x 2.40
	23-520	24 x 0.90
		24 x 7⁄8
	44-531	24 x 1 5⁄8 x 1 1⁄2
	40-534	24 x 1 ½
	20-540	24 x ¾
	23-540	24 x 0.90
		24 x 7⁄8
	25-540	24 x 1.00
	30-540	24 x 1.20
	32-540	24 x 1 3⁄8 x 1 1⁄4
	37-540	24 x 1 3⁄8
	40-540	24 x 1 3⁄8 x 1 1⁄2
	22-541
	25-541		600 x 25A
	28-541		600 x 28A
	32-541	24 x 1 3⁄8 x 1 1⁄4 NL	600 x 32A
	37-541		600 x 35A

	ETRTO	Inch	French
25"	57-520	25 x 2.25
26"	20-559	26 x 3⁄4
	23-559	26 x 0.90
		26 x 7⁄8
	25-559	26 x 1.00
	28-559	26 x 1.10
	30-559	26 x 1.20
	32-559	26 x 1.25
	35-559	26 x 1.35
	37-559	26 x 1.40
		26 x 1 5⁄8 x 1 3⁄8
	40-559	26 x 1.50
	42-559	26 x 1.60
	44-559	26 x 1.625
	44-559	26 x 1.75
	47-559	26 x 1.75
		26 x 1.80
		26 x 1.85
		26 x 1.90
	50-559	26 x 2.00
		26 x 1.90
		26 x 1.95
	54-559	26 x 2.10
		26 x 1.95
		26 x 2.125
	57-559	26 x 2.25
		26 x 2.125
		26 x 2.20
	60-559	26 x 2.35
	62-559	26 x 2.40
		26 x 2.50
	64-559	26 x 2.50
	65-559	26 x 2.60
	70-559	26 x 2.75
	75-559	26 x 3.00
	95-559	26 x 3.70
		26 x 3.80
	100-559	26 x 4.00
	115-559	26 x 4.50
	120-559	26 x 4.80
	20-571	26 x 3⁄4
	23-571	26 x 7⁄8	650 x 23C
	40-571	26 x 1 ½ CS	650 x 38C
		26 x 1 3⁄8 x 1 1⁄2 NL
	47-571	26 x 1 ¾	650 x 45C
			650 CS Confort
	54-571	26 x 2 x 1 ¾	650 x 50C
	20-590	26 x ¾	650 x 20A
	25-590	26 x 1.00	650 x 25A
	28-590	26 x 1 3⁄8 x 1 1⁄8	650 x 28A
	32-590	26 x 1 3⁄8 x 1 ¼	650 x 32A
	37-590	26 x 1 3⁄8	650 x 35A
	40-590	26 x 1.50	650 x 38A
		26 x 1 3⁄8 x 1 ½
	42-590	26 x 1 5⁄8	650 x 40A
	32-597	26 x 1 1⁄4
27"	40-609	27 x 1 ½
	20-630	27 x ¾
	22-630	27 x 7⁄8
	25-630	27 x 1.00
		27 x 1 1⁄16
	28-630	27 x 1 1⁄8
	32-630	27 x 1 ¼
	35-630	27 x 1 3⁄8
27.5"	28-584	26 x 1 1⁄8 x 1 1⁄2	650 x 28B
	32-584		650 x 32B
	35-584	27.5 x 1.35	650B
		26 x 1 3⁄8 x 1 1⁄2	650 x 35B
	37-584	27.5 x 1.40	650B
		26 x 1 1⁄2 x 1 3⁄8	650 x 35B
			650 Standard
	40-584	27.5 x 1.50	650B
		26 x 1 5⁄8 x 1 1⁄2	650 x 38B
	44-584	27.5 x 1.65	650B
		26 x 1 5⁄8 x 1 2⁄2	650 x 42B
			650B Semi-Confort
			650B ½ Ballon
	47-584	27.5 x 1.75	650B
	50-584	27.5 x 2.00	650B
	54-584	27.5 x 2.10	650B
		26 x 1 ½ x 2
	57-584	27.5 x 2.25	650B
	60-584	27.5 x 2.35	650B
	62-584	27.5 x 2.40	650B
	64-584	27.5 x 2.50	650B
	65-584	27.5 x 2.60	650B
	70-584	27.5 x 2.75	650B
	74-584	27.5 x 2.90	650B
	75-584	27.5 x 3.00	650B
28"	18-622	28 x ¾	700 x 18C
	19-622		700 x 19C
			700 x 19
	20-622	28 x ¾	700 x 20C
	22-622	28 x 7⁄8	700 x 22C
			700 x 22
	23-622	28 x 0.90	700 x 23C
		28 x 7⁄8
	24-622		700 x 24C
	25-622	28 x 1.00	700 x 25C
		28 x 1 1⁄16
	26-622		700 x 26C
	28-622	28 x 1.10	700 x 28C
		28 x 1 5⁄8 x 1 1⁄8
	30-622	28 x 1.20	700 x 30C
	32-622	28 x 1.25	700 x 32C
		28 x 1 5⁄8 x 1 ¼
	33-622	28 x 1.30	700 x 33C
	35-622	28 x 1.35	700 x 35C
	37-622	28 x 1.40	700 x 35C
		28 x 1 5⁄8 x 1 3⁄8
	40-622	28 x 1.50	700 x 38C
		28 x 1 5⁄8 x 1 ½
	42-622	28 x 1.60	700 x 40C
	44-622	28 x 1.625	700 x 42C
	47-622	28 x 1.75	700 x 45C
	50-622	28 x 2.00
		29 x 2.00
		28 x 1.90
	55-622	28 x 2.15
		29 x 2.15
	60-622	28 x 2.35
		29 x 2.35
	32-635	28 x 1 ½ x 1 1⁄8	770 x 28B
			700 x 28B
			700B Course
	40-635	28 x 1 ½	700 x 38B
		28 x 1 ½ x 1 5⁄8	700B Standard
	44-635	28 x 1 5⁄8 x 1 ½	700 x 42B
	28-642	28 x 1 5⁄8 x 1 ½	700 x 28A
	37-642	28 x 1 3⁄8	700 x 35A
29"	50-622	29 x 2.00
		28 x 2.00
	54-622	29 x 2.10
		28 x 2.10
	55-622	29 x 2.15
		28 x 2.15
	57-622	29 x 2.25
	60-622	29 x 2.35
		28 x 2.35
	75-622	29 x 3.00

Note: 28 inch and 29 inch tires have the same inner diameter of 622 mm and can be fitted on the same rims.

What is actually the difference between 28 and 29 inches?

The silliest answer to this question would be to say that the difference is exactly 1 inch. Another answer would be: There is no difference.

Both tire sizes have the same inner diameter of 622 mm and can therefore be fitted on the same rims.

In Europe, 28 inches is a traditional size for touring bicycles. In many countries it is even the most frequent tire size used. In countries outside Europe the rim diameter of 622 mm is only rarely used. Bicycle travelers who want to buy spare tires for a 28-inch touring bicycle anywhere in the world, can tell you a thing or two about it.

A few years ago 29 inch tires were introduced as a new wheel size for mountain bikes in the US. The marking was created, as the MTB tires are more voluminous and the outer diameter measures approximately 29 inches.

Both indications are, however, very imprecise. A less wide 28 inch tire, e.g. with a tire width of 23 mm, which is usual for a road bike, has in fact only an outer diameter of something more like 26 inches. In the case of a tire width of 40 mm,
it is more or less correct that the outer diameter measures 28 inches. In the case of very wide tires with 60 mm or more, the actual outer diameter measures almost 30 inches.

What are the advantages of the new wheel sizes 27.5 and 29 inches?

The new sizes are well established on the market and this is for good reason. The advantages of the large wheels outweigh the disadvantages. 29 inch wheels weigh a little more, are less manoeuvrable and possibly less stiff, but they roll clearly faster on rough surfaces especially in the terrain. The contact surface is bigger which makes for a significantly better tire grip.

There are, however, some bicycles which do not have enough clearance for a large 29 inch wheel, e.g. in the case of very small frame sizes and in particular bicycles with very long suspension travel. This is where the new wheel size 27.5 comes in.

Schwalbe will continue to offer all usual MTB tires for all three diameters.

Now let's dig up little into the Valves...

Which is the best valve?

There are three types that have become market standards and it is difficult to make any particular recommendation. The most important aspect is that the valve fits the rim valve hole and that an appropriate pump is available. Contrary to popular belief, major air retention differences are now a thing of the past. In any case, all Schwalbe valves provide excellent performance and are adapted to high-pressure use.

The classical bicycle valve or Dunlop valve is still the most common worldwide. Most cyclists are familiar with it. The valve core can easily be replaced and air can be released very quickly. Fitting a tube with a Dunlop valve is more awkward, as the valve core and locknut need to be removed in order to fit the valve through the valve hole. Inflation is only possible once the core and the nut are back in place.

With traditional Dunlop valves, it is impossible to check the inflation pressure. However, the special Schwalbe Dunlop valve allows a return airflow, so that it is now possible to check the inflation pressure with an Airmax pressure gauge.

Formerly it was difficult to inflate a tube with a Dunlop valve, but with today´s modern valve cores, this is no longer the case.

The Sclaverand valve is narrower than other valves (6 instead of 8 mm). It needs a smaller rim hole and is therefore particularly well suited for narrow racing bike rims. It is also approx. 4-5 g lighter than a car valve or Dunlop valve.

It can be locked manually with the knurled nut. Before inflating, the knurled nut must be loosened. First time users frequently have some problems. Also the thin top pin can be easily bent when attaching and removing the pump connector.

Caution: Be aware that using Sclaverand valve tubes on rims with larger valve holes often leads to a valve tear off when the sharp metal edges around the valve hole cut the valve stem off the tube.

The Auto/Car valve can be inflated very easily at a filling station and is pleasantly unproblematic. Older, as well as simple bicycle pumps are not compatible with car valves.

What is the purpose of a rim nut?

The rim nut fixes the valve in the rim. Some regard it as unnecessary. And indeed, you may well ride your bicycle without a rim nut. It is however helpful when attaching the pump connector, as particularly when the pressure is low the valve may fall inside the rim. With some rims there may be a rattle if the valve is not fixed.

The rim nut must only be tightened by hand. Never tighten the rim nut with pliers, as this can lead to tube damage.

What causes a valve tear off?

A valve tear off can occur if it was installed under tension.

Another frequent cause is installing a Sclaverand valve tube into a rim with a larger valve hole. The metal edge of the valve hole can shear the valve stem off the tube.

Caution: Be aware that there are also rims that have the correct valve hole of 6.5 mm on the outside, but a larger hole of 8.5 mm on the inside, which causes the problem. A nut that is excessively tightened just exacerbates the problem of tear off. The major role of the rim nut is to lock the valve in place at the time of inflation.

In most cases valve tear off is due to tire slip. Continual improvement in brake performance and low inflation pressures often cause the tire to slip on the rim. The tire movement then drags the tube and this can lead to the valve shearing off.

What can be done to prevent tire slip or valve tear off?

Schwalbe tire with L.S.T. coating on the bead

A higher inflation pressure considerably reduces the tire slip. Of course a higher tire pressure is not always desired.

We implement Limited Slip Technology (LST) in Schwalbe MTB-folding and balloon tires. The tire bead is coated with a special rubber layer that produces a dramatic reduction in tire/rim slip.

The Schwalbe Downhill tube has a highly reinforced valve foot.

Theoretically, the use of talcum powder is also helpful. This can reduce the friction between tire and tube. However in practice, if talcum powder gets between tire and rim, it will increase the problem.

Some rims have such slippery surfaces that even LST does not suffice one hundred percent. It will help if the rim contact area with the tire is lightly abraded with sandpaper (180 grade). This considerably increases the friction between tire and rim.

The problem is very much reduced with disc brakes because the rims do not get hot through braking.

There is no valve tear off with tubeless tires. The tire can move without causing problems.

Courtesy: Schwalbe Germany, our channel partners for tires & tubes solutions.