How to Read a Tyre Size: What 205/55 R16 91V Actually Means

Every tyre carries a code on its sidewall — something like 205/55 R16 91V. This tells you the tyre's width, profile, construction, rim size, load rating, and speed rating. Understanding it takes under two minutes and ensures you always order the right replacement.

Breaking down 205/55 R16 91V

205 — Section width (millimetres)

The first number is the tyre's width measured in millimetres from sidewall to sidewall when correctly fitted and inflated. A wider tyre (e.g. 225, 235) gives more contact patch with the road; a narrower tyre (e.g. 185, 195) is more efficient.

55 — Aspect ratio (profile)

This is a percentage. It means the tyre's sidewall height is 55% of its width — so 55% of 205mm = approximately 113mm of sidewall height. A lower aspect ratio (e.g. 40, 45) is a lower-profile tyre; higher (e.g. 65, 70) is a taller sidewall. Low-profile tyres generally handle better but give a firmer ride and are more prone to pothole damage.

R — Radial construction

Almost every modern car tyre is radial (R). You may occasionally see D (diagonal/cross-ply) on older vehicles or trailers. Radial and diagonal tyres must never be mixed on the same axle.

16 — Rim diameter (inches)

The diameter of the wheel the tyre is designed to fit, measured in inches. This must exactly match your wheel size. Common sizes range from 14" on smaller city cars to 20"–22" on SUVs and executive saloons.

91 — Load index

A code representing the maximum weight the tyre can carry when properly inflated. 91 = 615kg per tyre. It's important not to fit a tyre with a lower load index than the manufacturer specifies — this is both illegal and dangerous on commercial vehicles and vans.

V — Speed rating

The maximum sustained speed the tyre is designed for. V = 149mph. Common ratings include T (118mph), H (130mph), V (149mph), W (168mph). You should not fit tyres with a lower speed rating than your car's top speed capability.

Where to find your tyre size

The easiest place is the sidewall of your existing tyre — look for the three-number sequence starting with the tyre width. You can also find it in your vehicle's handbook, on a sticker inside the driver's door frame, or on the fuel filler flap. Some cars have different sizes front and rear (staggered fitment).

What if I need to check by registration plate?

Your vehicle's recommended tyre size is listed in the manufacturer specification. If you're unsure, tell us your registration number when you call and we can confirm the correct size before dispatch.

Do I have to match the tyre exactly?

Width, rim diameter, load index, and speed rating must match (or exceed) the original specification. The aspect ratio can sometimes vary by one size (e.g. 55 to 60) without affecting safety, but it will change the overall tyre diameter slightly, which can affect speedometer accuracy and — on vehicles with TPMS — trigger sensor warnings.