A tyre's sidewall carries a short code that says exactly what it is — its size, what it can safely carry, the speed it is built for, and the conditions it suits. A typical example reads 205/55 R16 91V, and once each part makes sense, choosing the right tyre stops being guesswork.
How a tyre size reads
The same order applies to almost every car tyre on UK roads:
| Part | Example | Meaning |
|---|---|---|
| Width | 205 | Tread width in millimetres |
| Profile | 55 | Sidewall height as a percentage of the width |
| Construction | R | Radial (standard for modern car tyres) |
| Wheel | 16 | Fits a 16-inch wheel |
| Load index | 91 | Maximum load per tyre (615kg) |
| Speed rating | V | Maximum rated speed (149mph) |
The two parts drivers most often misread are the profile — which is a percentage, not a measurement — and the load and speed ratings at the end, which must never drop below what the car needs.
What the rest of the sidewall says
Beyond the size, the sidewall describes what a tyre is built for: XL or Reinforced for a stronger casing, M+S for a self-declared mud-and-snow label, the three-peak snowflake for tested winter grip, and small carmaker codes that show a tyre was tuned for a specific manufacturer.
Each of these has its own guide below.
All sizes & markings guides
Guides for this pillar are being written.