How to read your tyre size

A tyre sidewall contains masses of information about every aspect of the tyre’s construction and design. The most important information needed when replacing your tyres is detailed and explained below.



Tyre Width

Also referred to as the “section width” of the tyre. This is the size in mm if you were to measure the tyre from sidewall to sidewall.



This is known as the “aspect ratio” and is expressed as a number which refers to the tyre’s height as a percentage of its width.

In our example, the tyre’s width is 205mm and the aspect ratio is 55% of that, or 112.75mm.


Rim Diameter

The “R” indicates that the tyre is of radial construction. Almost every tyre manufactured now is constructed this way with cords running through the tyre at 90° to the direction of travel.

The number is the diameter in inches of the wheel size the tyre fits.


Load Index and Speed Rating

The numbers are the load index of the tyre and indicate the maximum load the tyre may carry with reference to the maximum speed denoted by the letter. These refer to the tables below.

Our example has a load index of 91 or 615Kgs per tyre at a maximum speed V or 149 mph.