Tire Dimensions

• What is the exact circumference of my tire?
• Why is it that tires are often actually narrower than the ETRTO tire section width?
• Will the tire fit my frame?
• Which tire fits which rim?
• Can I use a narrower rim?

What is the exact circumference of my tire?

In order to accurately program a bicycle computer it is generally necessary to enter the exact tire circumference.

The tire circumference varies depending on the rim, the tire pressure and the load on the tire. For these reasons, it is not possible to list exact tire circumferences.

In order to accurately program a bicycle computer, we recommend a simple rolling test with the rider on the bicycle.

The approximate tire circumferences for the most common sizes are listed in the table on the right.

Why is it that tires are often actually narrower than the ETRTO tire section width?

The width standard of a tire is established on quite wide, standard rims. Yet in practice, rims that are in general use are narrower than standard and, in turn, this leads to tires becoming slightly narrower.

In order to ensure that tires have sufficient frame clearance, tire manufacturers generally prefer to keep production closer to the lower end of the permitted tolerance (+/- 3mm).

As carcass materials have improved greatly over recent years, it means that carcasses stretch less after fitment. In order to correct this phenomenon, over the past few years we have used slightly wider carcasses, so that the actual widths are now much closer to the standard widths.

Will the tire fit my frame?

The question whether the tires will fit into a particular frame is often asked in relation to our ultra-wide tires.

It is easy to appreciate that with the large number of different bicycle models we are unable to check the compatibility of all frames and tires. So, the following list shows the exact diameters and widths of our ultra-wide tires. This should allow verification that there is sufficient frame clearance for fitment of the selected tire.

Which tire fits which rim?

The inner diameter of the tire must match the rim bead seat diameter. For instance a tire size 37-622 fits on a 622 x 19C rim. The inner diameter of the tire corresponds to the rim bead seat diameter of 622 mm.

Furthermore, the tire section width must match the rim width. The following table shows possible combinations of tire section widths with rim widths according to ETRTO.


European Tire and Rim Technical Organization
Standards Manual - 2007

Can I use a narrower rim?

Wide tires are often fitted on narrower rims, as with Mountain Bikes, and also our BIG-APPLE tire. This saves weight, but it is also because very few wide rims are actually available in the market.

The rim manufacturer should be consulted before such fitment and only if they judge it safe. In order to prevent excessive stress on the rim, we advise not to inflate the tire to maximum pressure.

As a general guide, MTB tires of say 54 mm width fitted on standard 17C and 19C rims should not be inflated to more than 55 psi. Very wide tires of ca. 60mm fitted on narrow rims should not be inflated to more than 45 psi. Under no circumstances should rims of less than 17 mm be used.