The first set of numbers, 205 in this instance, refers to the width of the tyre in millimetres. The second number, 55, is known as the ‘profile’ or ‘ratio’ of the tyre. Essentially, this refers to the height of the tyre sidewall – the bigger the number, the more sidewall you’ll have.

The letter refers to what type of tyre you have, with the ‘R’ in this case referring to ‘radial’, the tyre type which is fitted to all road cars. Finally, the number at the end is the diameter of the wheel rim in inches. The last letter represents the type of tyre, in this case “V” stands for the speed rating of a on road tyre.