Tire Ratings and Sizes

Different sized tires on the rear of a vehicle affect the ABS braking system. This can result in the amber ABS warning light. The tire rating and sizing system are broken into easy to understand sections that describe size, load, and speed ratings.

Tire size and rating chart.

This tire size (P225/60R16 97Z) will help describe the meaning of these different sections. The (P) stands for the P-metric size. P-metric means that it's fitted for passenger vehicles like cars, light trucks, SUV's and minivans. A P-metric tire has a 1/4 ton or a 1/2 ton load capacity. The (LT) prefix stands for the light truck metric, and LT tires typically have a 3/4 ton to 1-ton capacity.

The next three digits (225) following the P-metric indicate the tire's section width. The section width of a tire is the measurement of the mounted tire's widest part, between the inner sidewall and the outer sidewall. This number is in metric millimeters. It can be converted to inches by dividing by 25.4.

Following the section width is a two-digit number that indicates the tire's profile or sidewall aspect ratio. This section indicates the tire's height from the edge of the tire's rim to the tread. This number is a percentage of the tires section width. Aspect ratio is sometimes referred to as section height.

The next section will typically be an R because most tires sold today are radial tires. A (D) indicates the tire is a diagonal bias-ply. These tires are not as common as they used to be. This is followed by the size of the tire or rim the tire will fit. This number is usually in inches (16), but can be in millimeters (390) on bigger tires.

The last three digits indicate the tire's service description. The first two digits are the tires load rating, which indicates the tire's load-carrying capacity. Sometimes there's no letter preceding the three-digit number. This means the tire was designed for European vehicles and may have slightly different load capacities. If the series ends with a C, the tire was designed for heavier load capacities. The final digit (Z) is the tire's speed rating.