A tyre sidewall can look like a collection of numbers and letters, but each part tells you something important about the tyre. A common example is 205/55 R16 91V.
What does 205/55 R16 mean?
205 millimetres is the nominal width of the tyre from sidewall to sidewall.
The sidewall height is 55% of the tyre width.
R means the tyre uses radial construction, which is standard on most modern passenger cars.
The tyre is designed to fit a 16-inch wheel.
What do 91V mean?
The numbers and letters after the rim diameter are normally the load index and speed rating. A load index identifies the tyre’s maximum load capacity according to the applicable tyre standard, while the speed rating indicates the tyre’s rated maximum speed under specified conditions.
For an actual vehicle, always use the tyre size, load index and speed rating recommended by the vehicle manufacturer. Do not choose a replacement tyre from size alone.
How to find your correct tyre size
- Read the full marking on the current tyre sidewall.
- Check the vehicle owner’s manual for the manufacturer’s approved sizes.
- Check the tyre information label on the vehicle, where fitted.
- Compare width, aspect ratio, rim diameter, load index and speed rating.
- Confirm the replacement tyre is suitable for your vehicle and intended use.
Why tyre size matters
The correct tyre specification helps preserve the vehicle’s designed handling, braking characteristics, load capacity and wheel fitment. Fitting an incorrect size can affect clearance, speedometer readings, handling and other vehicle characteristics.
If you are unsure, check the manufacturer’s specification or consult a qualified tyre professional before purchasing.