How to Read Your Tyre Size — A Simple Guide to Tyre Markings

Decoding Your Tyre Sidewall

Your tyre sidewall contains a string of numbers and letters that tell you everything about the tyre. Understanding them means you can order the right replacement without confusion. Let's decode a typical example: 205/55 R16 91V

205 — Tyre Width

The first number (205) is the tyre width in millimetres — measured across the widest point of the tyre from sidewall to sidewall when properly mounted and inflated. Common widths range from 145mm (small city cars) to 325mm (high-performance vehicles).

55 — Aspect Ratio

The second number (55) is the aspect ratio — the sidewall height expressed as a percentage of the tyre width. A 55 aspect ratio means the sidewall height is 55% of 205mm = 112.75mm. Lower aspect ratio numbers (e.g., 35, 40) mean a lower-profile, sportier look with less sidewall cushioning.

R — Radial Construction

The letter R indicates radial construction — by far the most common tyre construction type. Virtually all modern car tyres are radial.

16 — Rim Diameter

The number after R (16) is the wheel rim diameter in inches. This must match your wheel exactly — it's not interchangeable.

91 — Load Index

The load index (91) indicates the maximum load the tyre can carry when properly inflated. 91 = 615kg per tyre. Never fit a tyre with a lower load index than your vehicle requires.

V — Speed Rating

The final letter (V) is the speed rating — the maximum safe sustained speed. V = 149mph (240km/h). Common ratings: T=118mph, H=130mph, V=149mph, W=168mph, Y=186mph. Always match or exceed your original speed rating.

Where to Find Your Tyre Size

• On the sidewall of your existing tyres
• In your vehicle handbook
• On the driver's door jamb sticker
• On the fuel filler cap