The Main Size Code
Take a typical marking such as 205/55 R16 91V. The first number — 205 — is the tyre width in millimetres. The second number — 55 — is the aspect ratio, meaning the sidewall height is 55% of the tyre width. R indicates radial construction, which is standard on all modern cars. The 16 is the wheel diameter in inches.
Load and Speed Index
The 91 is the load index — a code indicating the maximum weight each tyre can carry (91 equates to 615kg). The V is the speed rating, meaning the tyre is approved for sustained speeds up to 240km/h (149mph). You must never fit a tyre with a lower speed rating than your car's approved specification, even if it fits the wheel.
Other Markings to Know
XL or Extra Load indicates a reinforced tyre capable of carrying higher loads — important for SUVs and vans. M+S means the tyre is rated for mud and snow. The three-peak mountain snowflake symbol (3PMSF) confirms the tyre meets the more rigorous winter performance standard. RF or RunFlat indicates the tyre can be driven on after a puncture.
The Manufacturing Date
Look for a four-digit code beginning with DOT on the sidewall. The last four digits give the week and year of manufacture — for example, 2423 means the 24th week of 2023. Any tyre over six years old should be inspected by a professional regardless of tread depth.
Need Help Identifying the Right Tyre?
Newport Mobile Tyres will identify the correct tyre specification for your vehicle from your registration number. Call 01633 855 522 and we'll recommend the right tyre at the right price, then fit it wherever your car is parked in Newport or South Wales.
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