By Ako Katka, AK Mobile Tyres • 2025-03-28 • 490-word guide
The string of numbers on your tyre sidewall — like 205/55R16 91V — looks complicated but follows a simple pattern. Understanding it means you can confidently order replacement tyres, check compatibility, and communicate clearly with tyre fitters.
| Code | What It Means |
|---|---|
| 205 | Tyre width in millimetres (across the tread) |
| 55 | Aspect ratio — sidewall height as a % of width (55% of 205mm = 112.75mm sidewall) |
| R | Radial construction (virtually all modern tyres) |
| 16 | Wheel rim diameter in inches |
| 91 | Load index — maximum load per tyre (91 = 615 kg) |
| V | Speed rating — maximum speed (V = 149 mph / 240 km/h) |
Your tyre size is printed on the sidewall of your existing tyre. You'll also find the manufacturer's recommended size in:
Speed ratings indicate the maximum speed the tyre is designed to handle continuously. You should never fit a tyre with a lower speed rating than the manufacturer specifies:
You should always fit the size specified by the vehicle manufacturer. Fitting a different width or aspect ratio can affect:
Minor variations (e.g. plus-sizing to a larger rim) are sometimes done for aesthetic reasons but should only be done with professional advice.
The DOT code includes the manufacture date. The last 4 digits tell you the week and year the tyre was made — e.g. "2319" means week 23 of 2019.
XL (Extra Load) or Reinforced (RF) means the tyre has a higher load capacity than a standard tyre of the same size. Always replace an XL tyre with another XL tyre.
No — tyres on the same axle must always be the same size, speed rating, and ideally the same brand and model. Mixing can cause dangerous handling imbalances.
Yes — call 07549 328819 with your tyre size and we'll check availability, give you a price, and book a fitting at your location in West London.
AK Tyres covers Hayes, West London and surrounding areas 24/7. We come to you — home, work, or roadside.
📞 Call 07549 328819