How to Read Your Tyre Size
In 205/55R16, 205 is the nominal tyre width in millimetres, 55 is the sidewall height as a percentage of width, R means radial construction, and 16 is the wheel diameter in inches. Also check your vehicle’s required load index, speed rating and fitment specifications before buying.
Where to find your tyre size
Your tyre size is printed on the sidewall of every tyre on your car. It looks like a string of numbers and letters, for example 205/55R16 91V.
You can also find the recommended size in your owner's manual and on the placard inside the driver's door jamb. The placard shows the size your vehicle was designed for, which is the safest choice when replacing tyres.
What each number means
Width (205): the width of the tyre in millimetres, measured from sidewall to sidewall.
Aspect ratio (55): the height of the sidewall as a percentage of the width. A lower number means a shorter, sportier sidewall; a higher number means a taller, more comfortable one.
Construction (R): 'R' means radial, which is standard on almost all modern passenger tyres.
Rim diameter (16): the diameter of the wheel the tyre fits, in inches.
Load index (91): a code for the maximum weight the tyre can carry. Always match or exceed your vehicle's requirement.
Speed rating (V): the maximum safe speed for the tyre. Match or exceed the rating specified for your car.
Can you change tyre size?
Sticking with the size on your door placard is the safest option. Changing width, profile or rim diameter can affect your speedometer accuracy, handling, and in some cases your insurance or roadworthy.
If you want to fit a different size — for example a plus-size wheel upgrade — talk to our team first so we can check the new size keeps your overall rolling diameter and load rating correct.
Sources and further reading
Frequently asked questions
Do all four tyres need to be the same size?
In most cases yes. Mixing sizes can affect handling and, on AWD vehicles, can damage the drivetrain. Some performance cars use a different size front and rear (a staggered setup) — check your placard.
What does the speed rating letter mean?
It's the maximum safe sustained speed for the tyre. Common ratings are T (190km/h), H (210km/h), V (240km/h) and W (270km/h). Always fit tyres that match or exceed your vehicle's specified rating.