ISO 5775

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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.

Tyre and Rim Technical data 01-en.png

Tires[edit]

Wired-edge tires[edit]

Wired-edge tires can be mounted on straight-side or crochet-type (aka hook bead) rims. Such tires are designated with their nominal 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[edit]

The standard defines a set of nominal section widths for wired-edge tires and lists recommended rim widths for each:

Nominal section
width of tire
Recommended rim widths
Straight-side rim Crochet-type rim
16 - 13C
18 - 13C
20 - 13C
23 16 13C, 15C
25 16, 18 13C, 15C, 17C
28 16, 18, 20 15C, 17C, 19C
32 16, 18, 20 15C, 17C, 19C
35 18, 20, 22 17C, 19C, 21C
37 18, 20, 22 17C, 19C, 21C
40 20, 22, 24 19C, 21C, 23C
44 20, 22, 24, 27 19C, 21C, 23C, 25C
47 20, 22, 24, 27 19C, 21C, 23C, 25C
50 22, 24, 27, 30.5 21C, 23C, 25C
54 27, 30.5 25C
57 27, 30.5 25C
62 27, 30.5 -

Older markings[edit]

Older markings of wired-edge tires can be converted to ISO 5775 designations with the help of the following table:

Tire size
designation
Old marking, outer diameter
Inches Millimetres
28-590 26 × 1⅜ × 1⅛
28-622 28 × 1⅝ × 1⅛ 700 × 28 C
28 × 1⅝ × 1¼ × 1⅛ 700 C Carrera
28-630 27 × 1¼ fifty
28-635 28 × 1½ 700 B
28-642 28 × 1⅜ × 1⅛ 700 × 28 A
32-239 12 × 1⅜ × 1¼ 300 × 32
32-248 12 × 1¼ 300 × 32 A
32-288 14 × 1⅜ × 1¼ 350 × 32
32-298 14 × 1¼ 350 × 32 A
32-340 16 × 1⅜ × 1¼ 400 A
400 × 32
32-349 16 × 1¼ NL 400 × 32 A
32-357 17 × 1¼
32-369 16 × 1¼
32-390 18 × 1⅜ × 1¼ 450 A
450 × 32
32-400 18 × 1¼ 450 × 32 A
32-438 500 × 32 ANL
32-440 20 × 1⅜ × 1¼ 500 A
500 × 32
32-451 20 × 1¼ 500 × 32 A
32-489 550 × 32 ANL
32-490 22 × 1⅜ × 1¼ 550 A
550 × 32
32-501 22 × 1¼ 550 × 32 A
32-508 22 × 1¼ × 1
32-540 24-1⅜ × 1¼
32-541 24 × 1⅜ × 1¼ NL 600 A
600 × 32 A
32-547 24 × 1¼
32-590 26 × 1⅜ 1¼ 650 × 32 A
32-597 26 × 1¼
32-622 28 × 1⅝ × 1¼ 700 × 32 C
28 × 1¼ × 1¾ 700 × C Course
32-630 27 × 1¼
32-635 28 × 1½ × 1⅛ 700 × 28 B
700 B Course
37-288 350 A Comfort
350 A 1/2 Balloon
37-298 14 × 1⅜
37-337 16 × 1⅜ ANL
37-340 16 × 1⅜ NL 400 A Comfort
400 A 1/2 Balloon
400 × 42 A
400 × 35 A
37-349 16 × 1⅜ NL
37-387 18 × 1⅜
37-390 450 A Comfort
450 A 1/2 Balloon
37-400 18 × 1⅜
37-438 20 × 1⅜ NL
37-440 500 A Comfort
500 A 1/2 Balloon
37-451 20 × 1⅜
37-489 22 × 1⅜ NL
37-490 550 A Comfort
550 A 1/2 Balloon
37-498 22 × 1⅜ × 1¼ NL
37-501 22 × 1⅜
37-540 24 × 1⅜
37-541 600 A Comfort
600 A 1/2 Balloon
600 × 35 A
37-565 25 × 1⅜
37-584 26 × 1½ × 1⅜
26 × 1⅜ × 1½
37-590 26 × 1⅜ 650 A
650 × 35 A
37-622 28 × 1⅝ × 1⅜ 700 × 35 C
28 × 1⅜ 1⅝
37-642 28 × 1⅜ 700 × 35 A
40-279 14 × 1½ 350 × 38 B
40-288 14 × 1½ NL 350 × 38
40-330 16 × 1½ 400 × 38 B
40-432 20 × 1½
40-440 20 × 1½ NL 500 × 38
40-534 24 × 1½
40-540 24 × 1⅜ × 1½
24 × 1½ × 1⅜
40-571 26 × 1½ C.S.
26 × 1⅝ × 1½ NL
40-584 26 × 1½ 650 × 35 B
650 × 38 B
40-590 26 × 1⅜ × 1½ NL
40-622 28 × 1⅝ × 1½ NL 700 × 38 C
40-635 28 × 1½ × 1⅜ 700 B Standard
28 × 1½ 700 × 35 B
700 × 38 B
44-194 10 × 1⅝
44-288 14 × 1⅜ × 1⅝ 350 A
350 × 42 A
44-340 16 × 1⅝
44-428 20 × 1⅝ × 1½
44-484 22 × 1⅝ × 1½
44-531 24 × 1⅝ × 1½
44-584 26 × 1½ × 1⅝ 650 B Semi-comfort
26 × 1⅝ × 1½ 650 B 1/2 Balloon
26 × 1¾ × 1½ 650 × 42 B
44-622 28 × 1⅝ 700 × 42 C
44-635 28 × 1⅝ × 1½
28 × 1½ × 1⅝
45-584 26 × 1.75 × 1½ 650 × 45 B
26 × 1½ × 1¾
47-203 12½ × 1.75 × 2¼
47-222 11 × 1¾
47-305 16 × 1.75 × 2
47-317 16 × 1¾
47-355 18 × 1.75 × 2
47-406 20 × 1.75 × 2
20 × 1.75
47-419 20 × 1¾
47-501 T 24 × 1¾ R 600 × 45 C
47-507 24 × 1.75 × 2
24 × 1.75
47-520 24 × 1¾
47-559 26 × 1.75 × 2
26 × 1.75
47-571 26 × 1¾ 650 × 45 C
26 × 1⅝ 650 C S.C.
47-622 28 × 1¾ 700 × 45 C
28 × 1.75
28 × 15/8 1¾
50-406 20 × 1.95
52-406 20 × 1.95
54-298 14 × 2 × 1¾
54-305 16 × 2
54-400 20 × 2 × 1¾
20 × 2 F 4 J
54-406 20 × 2.00
54-428 20 × 2
54-559 26 × 2.00
54-571 26 × 1¾ × 2
26 × 2 × 1¾
26 × 2 650 × 50 C
54-584 26 × 2 × 2½
26 × 1½ × 2
54-609 28 × 2
57-239 300 × 55 A
57-251 T 315 × 55
57-305 16 × 2.125
16 × 2.125 × 2
57-390 450 × 55 A
57-406 20 × 2.125
20 × 2.125 × 2
57-507 24 × 2.125
24 × 2.125 × 2
57-559 26 × 2.125
26 × 2.125 × 2
62-203 12½ × 2¼ 320 × 57
62-305 16 × 2.125
67-203 13 × 2½ 330 × 65
67-381 20 × 2½

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

Beaded-edge tires[edit]

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[edit]

ISO 5775-2 defines designations for bicycle rims. It distinguishes between

  • Straight-side (SS) rims
  • Crochet-type (C) rims
  • Hooked-bead (HB) rims

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 standard diameters of straight-side and crochet-type rims 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, 484, 489, 490, 498, 501, 507, 520, 531, 534, 540, 541, 547, 559, 565, 571, 584, 590, 597, 609, 622, 630, 635, 642

The standard diameters of hooked-bead rims are:

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

See also[edit]

External links[edit]

References[edit]

  • 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