To find your vehicle's original equipment tire size please check the following:
You can also check your existing tire's designation on the sidewall. However, there is no guarantee that this is the original tire size unless they came on the vehicle new.
This three-digit number represents the width of the tire in millimeters (mm), measured from sidewall to sidewall. Since this measure is affected by the width of the rim, the measurement is done when the tire is on its intended rim size.
The aspect ratio is the relationship of a tire's sidewall height to its section width, expressed as a percentage. In this example, the tire sidewall height is approximately 55% of the tire width. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall.
The diameter of the rim in inches.
An assigned number ranging from 0 to 130 that corresponds to the load-carrying capacity of a tire. The higher the tire's load index number, the greater its load carrying capacity.
The speed rating indicates the maximum speed at which a tire can carry a load under specified service conditions. Speed ratings for most car and light truck tires range from L (the lowest) to Z & (Y) (the highest).