Understanding Tyre Size Markings
Tyre sizes are written as a series of numbers and letters on the sidewall, such as 225/45 R17 91V. Each element has a specific meaning:
- 225 — Tyre width in millimetres from sidewall to sidewall.
- 45 — Aspect ratio, or profile height as a percentage of the width. Lower numbers mean lower, sportier profiles.
- R — Construction type. R means radial, which is standard on nearly all modern cars.
- 17 — Wheel rim diameter in inches.
- 91 — Load index, indicating the maximum weight each tyre can support.
- V — Speed rating, showing the maximum speed the tyre is designed for.
Where to Find Your Tyre Size
The easiest way is to read the sidewall of your current tyres. Alternatively, your vehicle handbook lists the recommended tyre sizes, and the inside of your driver's door frame often has a placard with size and pressure information.
Why Exact Size Matters
Fitting the wrong size can affect speedometer accuracy, handling, ride comfort, and even cause the tyres to rub against bodywork or suspension components. Always replace tyres with the exact size specified by your vehicle manufacturer unless you have professional guidance.
If you are unsure of your tyre size, a mobile tyre fitting technician can read it for you during a booking and ensure the correct replacements are supplied.
