Wikipedia

ISO 5775

ISO 5775 is an international standard for labeling the size of bicycle tires and rims. The system used was originally developed by the European Tyre and Rim Technical Organisation (ETRTO). It is designed to make tire sizing consistent and clear. It replaces overlapping informal systems that ambiguously distinguished between sizes. For example, at least 6 different "26 inch" sizes exist (just by American notation), and "27 inch" wheels have a larger diameter than American "28 inch" (French "700C") wheels. The Japanese Industrial Standards Committee also cooperates with ISO 5775. The corresponding Japanese standards are JIS D 9112 for tires and JIS D 9421 for rims.

Part 1, addressing tyres' designations and dimensions, was last published in August 2023 and Part 2, addressing rims, was last published in March 2021.

Part 1 considers tyres' nomenclature, size designation, marking, dimensions and compatibility with different rims and rim widths.

Part 2 considers both general requirements and specific requirements for 5 sub types of rim: straight-sided, tubeless straight-sided, hooked bead, crochet type (not the same as hooked bead type), and tubeless crochet type rims.

Tire designations and dimensions

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Part 1 considers separately the cases of

  1. clincher tyres mounted on straight sided type or crochet type rims, and
  2. hooked bead rims on which beaded edge tyres are mounted.

Clincher tyres on straight sided or crochet type rims

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Clincher tires can be mounted on straight-side or crochet-type rims. Crochet-type rims are not the same as hooked-bead rims. Such tires are designated with their nominal section width and their nominal rim diameter, separated by a hyphen (-). Both are measured in millimeters. A typical example of a tire marking according to ISO 5775-1 is:

32-597 inflate to 400 kPa
  • The first number (nominal section width) is essentially the width of the inflated tire (minus any tread).
  • The second number (nominal rim diameter) is the inner diameter of the tire when it is mounted on the rim. The corresponding circumference can be measured with a suitably narrow tape inside the rim.
  • The recommended inflation pressure is marked in kilopascals.

The standard notes that the minimum inflation pressure recommended is 300 kPa for narrow tires (25 mm section width or less), 200 kPa for other sizes in normal highway service, and 150 kPa for off-the-road service.

The inner width of the rim on which the tire is mounted should be about 65% of the tire's nominal section width for tires smaller than 30 mm and 55% for those larger.

The section height of a tire is usually identical to its section width (for tires less than 28 mm, 2.5 mm have to be added to the width to get the height). The overall diameter of the tire is then the rim diameter plus twice the tire's section height. The ISO 5775-1 standard also defines procedures for measuring tires and for calculating from the marking the maximum dimensions of a tire, which are needed by designers to determine clearance distances to other bicycle components.

Nominal section widths

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The standard defines for each tire size a rim design width based on the tire's nominal section width, and the range of rims widths which are recommended as acceptable to be used in service for a given tire section width.

Rim widths for each tire size (mm)
Nominal tire section width Design rim width Recommended acceptable rim width in use
Min Max Min Max
18 19 15 13 15
20 21 15 13 17
22 24 17 13 20
25 27 19 13 22
28 28 19 15 23
29 34 21 16 25
35 46 23 17 27
47 57 25 17 30
58 65 30 21 35
66 71 35 25 43
72 83 45 31 53
84 95 55 41 64
96 113 76 59 89
114 132 94 72 100

Older markings

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Note how in the below sorted table the "inches" measure is inconsistent with the mm measures, if height varies: Some 28-inch tires then have fewer mm than a 27-inch tire. 584 mm tires are also marketed as 27.5-inch (outer diameter) tires. Older markings of wired-edge tires can be converted to ISO 5775 designations with the help of the following table:

conversion table
Tire size
designation		 Old marking, outer diameter rim diam.
Inches Millimetres mm
28-590 26 × 1+3⁄8 × 1+1⁄8 590
28-622 28 × 1+5⁄8 × 1+1⁄8 700 × 28 C 622
28 × 1+5⁄8 × 1+1⁄4 × 1+1⁄8 700 C Carrera 622
28-630 27 × 1+1⁄4 630
28-635 28 × 1+1⁄2 700 B 635
28-642 28 × 1+3⁄8 × 1+1⁄8 700 × 28 A 642
32-239 12 × 1+3⁄8 × 1+1⁄4 300 × 32 239
32-248 12 × 1+1⁄4 300 × 32 A 248
32-288 14 × 1+3⁄8 × 1+1⁄4 350 × 32 288
32-298 14 × 1+1⁄4 350 × 32 A 298
32-340 16 × 1+3⁄8 × 1+1⁄4 400 A 340
400 × 32 340
32-349 16 × 1+1⁄4 NL 400 × 32 A 349
32-357 17 × 1+1⁄4 357
32-369 17 × 1+1⁄4 369
32-390 18 × 1+3⁄8 × 1+1⁄4 450 A 390
450 × 32 390
32-400 18 × 1+1⁄4 450 × 32 A 400
32-406 20 × 1+1⁄4 406
32-438 500 × 32 ANL 438
32-440 20 × 1+3⁄8 × 1+1⁄4 500 A 440
500 × 32 440
32-451 20 × 1+1⁄4 500 × 32 A 451
32-489 550 × 32 ANL 489
32-490 22 × 1+3⁄8 × 1+1⁄4 550 A 490
550 × 32 490
32-501 22 × 1+1⁄4 550 × 32 A 501
32-508 22 × 1+1⁄4 × 1 508
32-540 24-1+3⁄8 × 1+1⁄4 540
32-541 24 × 1+3⁄8 × 1+1⁄4 NL 600 A 541
600 × 32 A 541
32-547 24 × 1+1⁄4 547
32-590 26 × 1+3⁄8 1+1⁄4 650 × 32 A 590
32-597 26 × 1+1⁄4 597
32-622 28 × 1+5⁄8 × 1+1⁄4 700 × 32 C 622
28 × 1+1⁄4 × 1+3⁄4 700 × C Course 622
32-630 27 × 1+1⁄4 630
32-635 28 × 1+1⁄2 × 1+1⁄8 700 × 28 B 635
700 B Course 635
37-288 350 A Comfort 288
350 A 1⁄2 Balloon 288
37-298 14 × 1+3⁄8 298
37-337 16 × 1+3⁄8 ANL 337
37-340 16 × 1+3⁄8 NL 400 A Comfort 340
400 A 1⁄2 Balloon 340
400 × 42 A 340
400 × 35 A 340
37-349 16 × 1+3⁄8 NL 349
37-387 18 × 1+3⁄8 387
37-390 450 A Comfort 390
450 A 1⁄2 Balloon 390
37-400 18 × 1+3⁄8 400
37-406 20 × 1+3⁄8 406
37-438 20 × 1+3⁄8 NL 438
37-440 500 A Comfort 440
500 A 1⁄2 Balloon 440
37-451 20 × 1+3⁄8 451
37-489 22 × 1+3⁄8 NL 489
37-490 550 A Comfort 490
550 A 1⁄2 Balloon 490
37-498 22 × 1+3⁄8 × 1+1⁄4 NL 498
37-501 22 × 1+3⁄8 501
37-540 24 × 1+3⁄8 540
37-541 600 A Comfort 541
600 A 1⁄2 Balloon 541
600 × 35 A 541
37-565 25 × 1+3⁄8 565
37-584 27.5 × 2.0 × 2.5 584
26 × 1+3⁄8 × 1+1⁄2 650 × 37 B 584
37-590 26 × 1+3⁄8 650 A 590
650 × 35 A 590
37-622 28 × 1+5⁄8 × 1+3⁄8 700 × 35 C 622
28 × 1+3⁄8 1+5⁄8 622
37-642 28 × 1+3⁄8 700 × 35 A 642
40-279 14 × 1+1⁄2 350 × 38 B 279
40-288 14 × 1+1⁄2 NL 350 × 38 288
40-330 16 × 1+1⁄2 400 × 38 B 330
40-406 20 × 1+1⁄2 406
40-432 20 × 1+1⁄2 432
40-440 20 × 1+1⁄2 NL 500 × 38 440
40-534 24 × 1+1⁄2 534
40-540 24 × 1+3⁄8 × 1+1⁄2 540
24 × 1+1⁄2 × 1+3⁄8 540
40-559 24 × 1.5 559
40-571 26 × 1+1⁄2 C.S. 571
26 × 1+5⁄8 × 1+1⁄2 NL 571
40-584 26 × 1+1⁄2 650 × 40 B 584
650 × 38 B 584
40-590 26 × 1+3⁄8 × 1+1⁄2 NL 590
40-622 28 × 1+5⁄8 × 1+1⁄2 NL 700 × 38 C 622
40-635 28 × 1+1⁄2 × 1+3⁄8 700 B Standard 635
28 × 1+1⁄2 700 × 35 B 635
700 × 38 B 635
44-194 10 × 1+5⁄8 194
44-288 14 × 1+3⁄8 × 1+5⁄8 350 A 288
350 × 42 A 288
44-340 16 × 1+5⁄8 340
44-428 20 × 1+5⁄8 × 1+1⁄2 428
44-484 22 × 1+5⁄8 × 1+1⁄2 484
44-531 24 × 1+5⁄8 × 1+1⁄2 531
44-584 26 × 1+1⁄2 × 1+5⁄8 650 B Semi-comfort 584
26 × 1+5⁄8 × 1+1⁄2 650 B 1⁄2 Balloon 584
26 × 1+3⁄4 × 1+1⁄2 650 × 42 B 584
44-622 28 × 1+5⁄8 700 × 42 C 622
44-635 28 × 1+5⁄8 × 1+1⁄2 635
28 × 1+1⁄2 × 1+5⁄8 635
45-584 26 × 1.75 × 1+1⁄2 650 × 45 B 584
26 × 1+1⁄2 × 1+3⁄4 584
47-203 12+1⁄2 × 1.75 × 2+1⁄4 203
47-222 11 × 1+3⁄4 222
47-305 16 × 1.75 × 2 305
47-317 16 × 1+3⁄4 317
47-355 18 × 1.75 × 2 355
47-406 20 × 1.75 × 2 406
20 × 1.75 406
47-419 20 × 1+3⁄4 419
47-457 22 × 1.75 457
47-501 T 24 × 1+3⁄4 R 600 × 45 C 501
47-507 24 × 1.75 × 2 507
24 × 1.75 507
47-520 24 × 1+3⁄4 520
47-559 26 × 1.75 × 2 559
26 × 1.75 559
47-571 26 × 1+3⁄4 650 × 45 C 571
26 × 1+5⁄8 650 C S.C. 571
47-622 28 × 1+3⁄4 700 × 45 C 622
28 × 1.75 622
28 × 15⁄8 1+3⁄4 622
50-406 20 × 1.95 406
52-406 20 × 1.95 406
53-559 26 × 1.95 559
54-298 14 × 2 × 1+3⁄4 298
54-305 16 × 2 305
54-400 20 × 2 × 1+3⁄4 400
20 × 2 F 4 J 400
54-406 20 × 2.00 406
54-428 20 × 2 428
54-559 26 × 2.00 559
54-571 26 × 1+3⁄4 × 2 571
26 × 2 × 1+3⁄4 571
26 × 2 650 × 50 C 571
54-584 26 × 2 × 2+1⁄2 584
26 × 1+1⁄2 × 2 584
54-609 28 × 2 609
57-239 300 × 55 A 239
57-251 T 315 × 55 251
57-305 16 × 2.125 305
16 × 2.125 × 2 305
57-390 450 × 55 A 390
57-406 20 × 2.125 406
20 × 2.125 × 2 406
57-507 24 × 2.125 507
24 × 2.125 × 2 507
57-559 26 × 2.125 559
26 × 2.125 × 2 559
62-203 12+1⁄2 × 2+1⁄4 320 × 57 203
62-305 16 × 2.5 305
67-203 13 × 2+1⁄2 330 × 65 203
67-381 20 × 2+1⁄2 381

Such older markings can be appended to the ISO 5775 designation in parentheses.

Beaded-edge tires

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Beaded-edge tires are mounted on hooked-bead rims. They are marked with an overall diameter code and a nominal section-width code, separated by a cross (×). An example for such a marking is

20×1.375

Rims

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Part 2 defines designations for bicycle rims. It distinguishes between

  • Straight-side (SS) type rims
  • Tubeless straight-side (TSS) type rims
  • Crochet (C) type rims
  • Tubeless crochet type rims
  • Hooked-bead (HB) rims

Both crochet (C) and hooked-bead (HB) rims have inner profiles that curve inwards near the outside diameter of the rim to provide a hook that helps retain the tire bead under high pressure. On modern bikes crochet rims are most common and hooked bead rims are rare. The distinction is primarily that hooked-bead rims lack the defined bead seat of straight side and Crochet-type rims. The tire is held in position radially by the hook without a bead seat playing a role. Without a bead seat, the primary designation of the diameter in terms of the bead seat is not applicable, and the governing diameter is the OD.

Rims are designated by their nominal rim diameter and their nominal width, separated by a cross (×). Both are measured in millimeters. The rim type codes SS or HB precede the rim designation, whereas code C is appended to the nominal width. Examples:

SS 400×20, HB 422×25, 620×13C

The nominal width of a rim is the inner width between the straight sides or beads as one can easily measure it with a caliper (see the standard for drawings and exact measurement procedures).

The standard widths of straight-side rims are:

18, 20, 22, 24, 27, 30.5

The standard widths of crochet-type rims are:

13C, 15C, 16C, 17C, 19C, 21C, 23C, 25C

The standard widths of hooked-bead rims are:

20, 25, 27

The diameters of straight-side and crochet-type rims are measured as the bead seat diameter (BSD). Standard values are:

194, 203, 222, 239, 248, 251, 279, 288, 298, 305, 317, 330, 337, 340, 349, 355, 357, 369, 381, 387, 390, 400, 406, 419, 428, 432, 438, 440, 451, 457, 484, 489, 490, 498, 501, 507, 520, 531, 534, 540, 541, 547, 559, 565, 571, 584, 590, 597, 609, 622, 630, 635, 642

The diameters of hooked-bead rims are measured as the outside diameter of the rim (not the tire). Standard values are:

270, 321, 372, 422, 459, 473, 510, 524, 560, 575, 611

See also

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  • Sheldon Brown. "Tire Sizing".
  • "Technical information – bicycle tyres" (PDF). Schwalbe.. handbook by a German tyre manufacturer, includes detailed size tables

References

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  • International Standard ISO 5775-1:1997, Bicycle tyres and rims — Part 1: Tyre designations and dimensions
  • International Standard ISO 5775-2:1996, Bicycle tyres and rims — Part 2: Rims
  • JIS standard D 9421. (2009) (English): Bicycles — Rims
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