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International standard for labeling the size of bicycle tires and rims
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
Part 1 considers separately the cases of
clincher tyres mounted on straight sided type or crochet type rims, and
hooked bead rims on which beaded edge tyres are mounted.
Clincher tyres on straight sided or crochet type rims
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:
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
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
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+3⁄81+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+3⁄81+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 × 15⁄81+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
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
This section needs expansion. You can help by adding to it. (May 2008)
Rims
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:
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