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ISO 5775 ISO 5775 je mezinárodní standard pro označovaní velikosti cyklistických ráfků, plášťů a duší. Tento systém byl původně vyvinut Evropskou organizací pro technické značení velikostí kol. Nahrazuje předchozí nejednoznačný systém kde je například šest rozdílných velikostí v 26" palcech (a to jenom v americkém značení) a kde mají 27" palcová kola širší rozpětí než 28" palcová ('700C' podle francouzského značení).

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

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

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
 * 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, 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 standard diameters of hooked-bead rims are:


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