How to read the markings on your tyre sidewall
6 min readBy Wheel Fit
The short answer: the string you need when ordering a tyre looks like 205/55 R16 91V. That is width in millimetres, profile as a percentage, construction, rim diameter in inches, load index and speed rating.
Taking it apart
| Marking | Meaning |
|---|---|
| 205 | Section width in millimetres, sidewall to sidewall. |
| 55 | Aspect ratio: sidewall height as a percentage of the width. So 55% of 205mm. |
| R | Radial construction. Almost everything on the road is radial. |
| 16 | Rim diameter in inches. This one is not metric. |
| 91 | Load index — the maximum weight the tyre can carry. |
| V | Speed rating — the maximum speed it is certified for. |
A lower profile number means a shorter, stiffer sidewall. It looks sportier and responds faster, but it also means less rubber between your rim and the pothole.
How old is the tyre? The DOT code
Look for a four-digit number, often in an oval, after the letters DOT. It is a date, not a serial number:
- The first two digits are the week of manufacture.
- The last two are the year.
So 2523 means week 25 of 2023. This matters because rubber degrades with time as well as mileage. A tyre with plenty of tread that has sat on a caravan or a low-mileage car for a decade is not the same as a tyre made last year.
Other markings worth knowing
- C after the size — a commercial tyre, built for van loads. Not interchangeable with a car tyre of the same size.
- XL or Reinforced — a stronger casing with a higher load capacity.
- M+S, or a snowflake-in-a-mountain symbol — mud and snow, or a genuine severe-snow certification.
- RSC, ROF, ZP, RunOnFlat — run-flat construction, which varies by manufacturer.
- A rotation arrow — the tyre is directional and must go on the correct side.
- Tread wear indicators — small raised bars in the grooves marking the 1.6mm legal minimum.
Where to find your correct size
The tyre currently fitted is not automatically the right one — previous owners get it wrong. The manufacturer's specification is on a plate in the driver's door shut, sometimes inside the fuel flap, and always in the handbook.
If the fitted size and the door plate disagree, tell us when you call and we will work out which is correct for the vehicle.
