What do tyre size numbers mean?
The numbers on a tyre’s sidewall provide key details about its specifications, including width, aspect ratio, construction type, inner diameter, load capacity, and speed rating. For example, if your tyre displays a sequence like 205/55 R16 91V, each segment conveys important information. With a clear breakdown, these codes help you understand the tyre’s dimensions, design, and performance capabilities.
205 – Tyre Width (in millimetres)
This is the width of the tyre tread from sidewall to sidewall.
205 mm wide in this example.
55 – Aspect Ratio (Height as a % of Width)
This number shows the height of the tyre’s sidewall as a percentage of its width.
55 means the sidewall height is 55% of 205 mm = about 113 mm.
R – Radial Construction
The “R” means the tyre has radial construction – the most common type used in the UK and Europe. It’s how the internal layers are structured.
16 – Rim Diameter (in inches)
This tells you the size of the wheel (rim) the tyre is designed to fit.
So this one fits a 16-inch alloy or steel wheel.
91 – Load Index
This number shows how much weight each tyre can carry when properly inflated.
91 equals a load capacity of 615 kg per tyre. Always check your vehicle handbook to know what’s safe.
V – Speed Rating
The speed rating tells you the maximum speed the tyre can handle safely.
V means it’s rated for speeds up to 149 mph (240 km/h). Perfectly fine for UK motorways.
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