Breaking Down a Tyre Size Code
A typical tyre size marking looks something like 205/55 R16 91V. Each part of this code carries specific meaning. The first number — 205 — is the tyre width in millimetres. The second number — 55 — is the aspect ratio, representing the sidewall height as a percentage of the tyre width. The letter R indicates radial construction, which is standard on all modern passenger vehicles. The number 16 is the rim diameter in inches.
The final two characters — 91V in this example — form the load and speed index. The number 91 corresponds to a maximum load of 615kg per tyre (load ratings are referenced against a standardised table), while V indicates a maximum speed rating of 240 km/h. Fitting a tyre with a lower load or speed index than specified for your vehicle is both unsafe and potentially illegal.
Why Getting the Right Size Matters
Fitting the wrong tyre size affects far more than how your car looks. Incorrect dimensions alter your speedometer reading, change the handling characteristics of the vehicle, and may interfere with ADAS systems including lane assist, cruise control, and automatic emergency braking that rely on accurate wheel speed data.
An incorrect load rating means a tyre may fail under normal driving conditions — particularly relevant for drivers who regularly carry full passenger loads or tow. Always match or exceed the tyre specification listed in your vehicle handbook or on the sticker inside the driver door jamb.
Where to Find Your Correct Tyre Size
The easiest places to find your vehicle's required tyre size are the sticker on the inside edge of the driver's door, the inside of the fuel cap flap, or your vehicle handbook. All three will list the manufacturer-approved sizes for your specific model and trim.
When you book with Triumph Mobile Tyres, you can simply provide your vehicle registration number. Our team can cross-reference the correct tyre size for your vehicle from our database, saving you the effort entirely.
Need a Mobile Tyre Fitting?
Our technicians come to you — home, work, or roadside. Get a free quote in seconds or call us now.