Those numbers and letters on your tyre sidewall tell you everything about the tyre's size, load rating, and speed index. Here's how to decode them simply.
Every tyre has a string of numbers and letters moulded into its sidewall. For most drivers these look meaningless, but they contain vital information about the tyre's dimensions, construction, load capacity, and maximum speed. Here's how to decode a typical tyre marking – using 205/55R16 91V as our example.
The first number – 205 – is the tyre width in millimetres measured across the tread from sidewall to sidewall. The second number – 55 – is the aspect ratio, which is the height of the sidewall as a percentage of the width. So in this case the sidewall height is 55% of 205mm, which is approximately 113mm. Lower aspect ratio numbers (like 35 or 40) mean lower-profile tyres with a sportier appearance and more direct handling. Higher numbers (60, 65) mean a taller sidewall and a softer ride.
The letter R means radial construction – this is the case on virtually all modern tyres. The number after the R – 16 – is the diameter of the wheel rim the tyre fits, measured in inches. After the R code comes the load index (91 in our example), which indicates the maximum weight the tyre can support when fully inflated. 91 corresponds to 615kg per tyre. Finally, the speed rating letter (V in our example) indicates the maximum sustained speed the tyre is designed for. V means 149mph. Other common ratings include H (130mph), T (118mph), and W (168mph).
When buying replacement tyres, always match the width, aspect ratio, rim diameter, and meet or exceed the load index and speed rating of the original specification. If you're unsure, the team at Top Tech Mobile Tyres in Glasgow can look up the correct specification for your vehicle. Call 0141 673 5765 and we'll sort it for you.
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