Those numbers on your tyre sidewall might look like a code, but they're actually easy to read once you know what to look for. Here's a plain-English guide.
Walk around to the side of your car and look at one of your tyres. On the sidewall, you'll see a sequence of numbers and letters — something like 205/55 R16 91V. This isn't marketing copy. It's a precise specification that tells you exactly what tyre your vehicle needs.
Breaking Down the Numbers
Take 205/55 R16 91V as our example:
- 205 — This is the tyre width in millimetres, measured across the face of the tyre.
- 55 — This is the aspect ratio: the height of the tyre's sidewall as a percentage of the width. So in this case, the sidewall height is 55% of 205mm.
- R — Radial construction, which is standard on virtually all modern passenger tyres.
- 16 — The rim diameter in inches. Your wheels must match this.
- 91 — The load index. This tells you the maximum weight each tyre can support.
- V — The speed rating. V means the tyre is rated for sustained speeds up to 149mph.
Why Getting the Size Right Matters
Fitting the wrong tyre size isn't just an MOT failure waiting to happen — it can genuinely affect the handling and safety of your vehicle. A tyre that's too narrow provides less grip; one that's too wide may foul the wheel arch on full lock. The speed and load ratings also matter for insurance purposes.
Finding Your Tyre Size Without Looking at the Tyre
If you're not sure, there are three other places to look: the vehicle handbook, the sticker on the inside of the driver's door frame, or simply enter your registration on our booking page and we'll find the correct size for you.
When booking mobile tyre fitting, always double-check the size — it saves time on the day of fitting and ensures we arrive with exactly what you need.
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