Finding the correct snow tire size for a vehicle involves learning to read the information on the sidewalls of tires, which displays the many aspects of sizing, including tire width, load index and rim diameter. Many tire manufacturers also abbreviate the type of vehicles best suited for certain tires: these letters show car and truck drivers which snow tires fit cars, trucks and vans.
In addition to the metric, which designates appropriate vehicle class, tire sidewalls include other information to help drivers match tires with their cars.
Following the vehicle class is a number expressed in millimeters. This number represents the tire width, which measures the distance between the two furthest edges of the sidewall. The aspect ratio and construction type follow.
Aspect ratio indicates percentage of tire height to width. Construction type, refers to a radial or diagonal design, which shows the tread type of the tires.
The rim diameter appears next; this number shows the longest distance of a wheel, and appears in inches or centimeters. The load index follows and indicates how much weight tires can carry. For most passenger cars, this number ranges between 75 and 100 pounds.
Lastly, speed ratings show drivers how fast they can drive vehicles with the tires at hand. These ratings range from the lowest, Q, to Z, the highest. Finally, manufacturers indicate the tires' suitability with a letter: "M" denotes use in mud, while "S" stands for snow. Most tires have a combination of these letters.