Tyre dimensions for quad tyres

Four-wheeler riders (and not only) are often faced with the problem of choosing the right tyre height and width for their vehicle. Historically, the development of tyre manufacturing has led to several different ways of marking tyre dimensions in different parts of the world. For this reason, it is sometimes difficult to compare actual tyre dimensions. Here is a brief overview of the most popular tyre markings for quad tyres.

In European countries, the DIN marking adopted by the Deutsches Institut fuer Normung (German Institute for Standardisation) is the most widely used. If you see the following numbers on a tyre, for example: 250/65-12, these numbers mean:

• 250 is the width of the tyre in millimetres;

• the number 65 is the height of the tyre (expressed as a percentage of the width). Here, the height is measured from the rim mounting edge to the top of the tread. In simpler terms, it is the 'thickness' of the tyre. If you want to get this figure in millimetres, you need to calculate 65 per cent of the tyre's width, i.e. 250 mm*65% = 162.5 mm.

• The number 12 means that the tyre is designed to fit on a 12 inch diameter rim.

Therefore, with this marking, the overall height of the tyre when placed on the base and measured to the top will be: 2 tyre 'thicknesses' 162.5 mm + 162.5 mm + (12 inch rim diameter). 1 inch = 25.4 mm. Total 162.5 mm + 162.5 mm + (12*25.4) = 629.8 mm.

Manufacturers who do not comply with DIN markings would mark an equivalent quad tyre: 25x10-12:

• Here the number 25 is the overall height of the tyre when placed on the base and measured to the top in inches. In millimetres this would be: 25inches *25.4 = 635 mm.

• The number 10 is the width of the tyre expressed in inches. In millimetres this would be 10 inches * 25.4 =254 mm

• The number 12 means that the tyre is suitable for fitting on a 12 inch diameter rim.

When converting tyre dimensions in inches and millimetres there may be slight differences in dimensions. Why manufacturers have chosen to indicate part of the dimensions in millimetres and part in inches on the markings remains unclear, but let that be the manufacturers' concern.

Dimensional Converter Online.