When the rider finds himself confronted with several dimensions such as 650A, 650B, 650C or 700A, 700B, 700C, he/she risks being confused and may think they are all identical: this is not the case.

It is impossible to use a 650A tire to replace a 650B or C. Similarly, a 700A cannot replace a 700B or C tire, because all these tires have different bead seat diameters.

The 650A tire has an interior bead seat diameter of 590 millimeters, the 650B has an interior diameter of 584 millimeters and the 650C has an interior diameter of 571 millimeters.

The 700A tire has an interior diameter of 642 millimeters, the 700B has an interior diameter of 635 millimeters and the 700C has an interior diameter of 622 millimeters.

Although all these tires have identical exterior diameters (650 or 700), because their widths are different, their inside diameters are different: 590 millimeters, 584 millimeters or 571 millimeters for the 650 and 642, 635, or 622 millimeters for the 700.

ATTENTION:

The old method of determining the interior diameter of a tire (exterior diameter – 2 times the section), does not work anymore for the new dimensions.

Examples:

700 x 20C PRO2 RACE (20 x 622)

700 x 23C PRO2 RACE (23 x 622)

700 x 25C PRO2 RACE (25 x 622)

For all these dimensions, the diameter to the seat
of 622 millimeters is used.