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European Tyre and Rim Technical Organisation

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The European Tyre and Rim Technical Organisation (ETRTO) exists to specify and harmonise sizes of rims and their associated pneumatic tyres across the European Union. ETRTO sizes apply to rims and tyres for vehicles of all types. It is probably most well-known for size standardisation of bicycle tires designations in millimeters, which replaces many older national methods for referring to tire sizes that are incompatible. The great advantage of ETRTO sizing is that it is unambiguous; previously, nominal dimensions were used which were interpreted in different ways by different countries and manufacturers - a problem for the end user.

ETRTO works in liaison with the International Organization for Standardization to develop relevant standards.[1]

Motivation

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Previously, one could for example risk buying a 28 inch tire for a 28 inch rim, with the result that the tire would not fit since 28" can refer to rim bead diameters of either 635 mm or 622 mm. Thus, a tire for one type of 28" inch rim will not fit the other, and vice versa. Another example is the rim sizes 406 mm and 451 mm, which both traditionally have been referred to as 20 inch (and obviously are not cross-compatible).

ETRTO solves these problems by precisely referring to rim bead diameters in millimeters.

Bicycle tire sizes

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The following is a list of different types of bicycle tires listed by bead diameter according to ETRTO:[2]

Rim bead diameter Traditional names
137 8 x 1 1/4
152 10 x 2
203 12 1/2 x "anything"
252(?) 12 x 1 5/8 French (254 tires may fit if the rim is padded with rim tape[2])
254 14 x 1.75
288 350a
298 14 x 1 3/8, Moulton Mini
305 16 x 1.75- x 2.125
317 16 x 1 3/4
335 16x 1 3/8 Polish children's bicycles
337 16 x 1 3/8
340 400a
349 16 x 1 3/8
355 18 x 1.5- x 2.125
369 17 x 1 1/4
390 450a
400 18 x 1 3/8,

18 x 1

406 20 x 1.5- x 2.125
419 20 x 1 3/4 Schwinn Juven
428 20 x 2 Swedish
438 20 x 1 3/8 NL, Dutch children's bicycles
440 500a
451 20 x 1 1/8;

20 x 1 1/4; 20 x 1 3/8; OS20 x 1.6, 1.75, 1.85

457 22 x 1.75;

22 x 2.1, 22 x 2.125, 22 x 2.3, 22 x 2.4

484 550b
489 22 x 1 1/8 NL, Dutch children's bicycles

22 x 1 3/8 NL

490 550a
501 22 x 1 3/8, British

22 x 1.00

507 24 x 1.5,

24 x 2.125

520 24 x 1,

24 x 1 1/8, 24 x 1 3/8, 24 x 1 3/4

534 24 x 1.5 Dutch
540 24 x 1 1/8,

24 x 1 3/8 (E.5),

541 600 A
547 24 x 1 1/4,

24 x 1 3/8 (S-5)

559 26", traditional size for mountain bikes, but also for fat bikes up to 127 mm tire width
571 26 x 1,

26 x 1 3/4, 650c

583 700d, special size made by GT Bicycles
584 650b,

26 x 1 1/2, 27.5"

590 26 x 1 3/8 (E.A.3),

650a

597 26 x 1 1/4,

26 x 1 3/8 (S-6)

599 26 x 1.25,

26 x 1.375, old American size

609 27 x 1 1/2, rare Danish size
622 700c,

28 x 1 5/8, 28 x 1 1/2 and others, (but see also 635), 29 inch, 28 x 1 1/2 F.13 Canada

630 27 x "anything" (except "27.5" and 609 mm
635 700b,

28 x 1 1/2, 28 x 1 5/8, 28 x 1 1/2 (old Swedish)

642 700a
686 32 inch
787 36 inch

See also

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References

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  1. ^ List of ISO committees in liaison with ETRTO
  2. ^ a b "Tire Sizing Systems". www.sheldonbrown.com. Retrieved 2025-05-07.
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