This string of numbers (in the image 255/55 R16) indicates the size of the tyre. This is important as you will need to ensure that any tyres you fit to your vehicle are the correct size as specified in your vehicle handbook. These numbers mean:
255 – Tyre Width
This indicates the width of the tyre in millimetres from sidewall to sidewall.
55 – Aspect Ratio
These digits express the height of the tyre sidewall expressed as a percentage of the tyre width. In this example, the tyre height is 55% of its width.
R – Tyre Construction
The letter ‘R’ indicates that the tyre is of radial construction, as most tyres manufactured today are. Other types of construction include ‘B’ (bias belt) and ‘D’ (diagonal).
16 – Wheel Diameter
This figure signifies the size of the wheel rim in inches that the tyre is intended to be fitted to.