Example: 225/45R17
The size is a sequence describing tire width, sidewall proportion, construction, and wheel diameter.
- 225 — approximate tread-section width in millimetres
- 45 — sidewall height as a percentage of the width
- R — radial construction
- 17 — wheel diameter in inches
What follows the size?
A tire may show something such as 94W after the size. The number is the load index and the letter is the speed rating. XL indicates Extra Load construction. Other markings may identify run-flat construction, winter certification, or original-equipment specifications.
Where to find the correct size
Check the tire-information placard inside the driver’s door opening or the owner’s manual. The number moulded onto an existing tire is useful only if the vehicle currently has the correct fitment.
Do not change tire size based only on whether it fits the wheel. Overall diameter, load capacity, wheel width, clearance, and vehicle requirements must all be checked.
This guide provides general tire information and does not replace the vehicle placard, owner's manual, tire-manufacturer instructions, legal requirements, or a physical tire inspection.