All About Tire Sizing
Choosing the right size is very critical. Make your tire size selection in strict accordance with vehicle documents and tire manufacturer recommendations. If the combined wheel and tire diameter are not correctly matched, there may be drastic differences in ride height, handling and incorrect speedometer readings.
For example, fitting 17-inch-diameter wheels to a car that is designed to have 14-inch-diameter wheels will change the ride height. That means the car body will be higher off the ground. There will also be a slight increase in top speed, and the speedometer will no longer be accurate. Finally, the car will accelerate slower.
What do all these letters and numbers mean on the tire itself? Here is all the information on the tire sidewall that will quickly help you understand.
1) The width of the tires in millimeters
2) Percentage height of the sidewall in relation to the width
3) Radial construction
4) Rim diameter in inches
5) Load index (the maximum load capacity of the tire)
6) Speed index (the maximum speed of the tire)
7) Self-Supporting Run-flat tire
8) Original Equipment Key (Only on Specific Vehicles, OE is also a key driver for the development of ultra-high performance tires, MOE,POL,VOL,N1,N2,J,LR etc)
9) Suitable for mud and snow conditions
10) Compliant with Department of Transportation motor vehicle safety standards
11) Week of manufacture
12) Year of manufacture
Load index
The load index rating is the maximum capacity of a passenger car tire, calculated from the maximum permissible axle load range between two tires.
Speed index
The speed index rating is also a relevant factor when choosing a tire. The tire’s speed capability must be at least equivalent to the top speed of the vehicle. Its speed rating indicates the maximum permissible speed (at full load) of a tire, and whether it is appropriate for your car.