The tyre markings convey size, aspect ratio, build construction, diameter, load index, and speed rating and indicate if the tyre is rated for mud and snow.
On the sidewall of the tyre there will be a series of number which describe the tyres specifications.
These should be matched to the car specified by the car manufacturer.
Below is a description of these markings:
- Tyre width
This three-digit number refers to the overall width of the tyre in millimeters.
- Aspect ratio
The relationship between tyre height and tyre width. The higher the number, the taller the sidewall.
- Primary speed rating
This specifies the maximum speed at which a tyre is certified to carry its maximum load. Primary speed ratings range from A (lowest) to Z (highest). (Some tyres also carry more specific secondary ratings.)
The letter R indicates radial-ply as opposed to bias-ply tyre construction.
- Wheel diameter
This number indicates the size of wheel the tyre is designed to fit onto.
- Load index
A relative scale that indicates how much weight the tyre is certified to carry at maximum inflation. It can range from zero to 279. The higher the number, the greater the load-carrying capacity.
- Mud and snow
The letters M and S indicate that the tyre meets the Rubber Manufacturers Association's standards for mud-and-snow usage.