Information about 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).

Tires

Wired-edge tires

Wired-edge tires can be mounted on straight-side or crotchet-type rims. Such tires are designated with their nominal rim diameter and their nominal width, separated by a hyphen (-). Both are measured in millimeters. A typical example of a tyre 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.

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

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

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

Rims

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

• Straight-side (SS) rims
• Crotchet-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 crotchet-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 crotchet-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

ERD - Effective Rim Diameter

ERD is a measure of rim size, useful for determining the appropriate spoke length. It is the distance between opposite nipple seats in the rim. The nipple seat is the surface of the rim where the nipple head sits. Because today rims come in largely varying designs, the distance from the tire seat to the nipple seat can vary significantly between rims of the same nominal (tire seat) diameter. Therefore the ERD has no fixed relationship to the ISO 5775-2 dimensions, it is an additional measure.

External links

• Tire Sizing by Sheldon Brown
• Hub and Rim Measurements by Robert Torre

References

• 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