Tire sizes are measured using millimeters (metric), or inches (high flotation). The first size we’ll go over is a metric size: P225/75R16
Tire Class: P
The tire class for this tire is “P” meaning it’s a passenger tire. “LT” stands for light truck, and “ST” is for trailer tires.
Section Width: 225
The section width is the width of the tread from sidewall to sidewall. In this example, it’s 225 millimeters.
Aspect Ratio: 75
The ratio of the width of the tire tread (section width) to the amount of rubber between the wheel and the tread is the aspect ratio. In this example, it’s 75%.
Tire Construction: R
R stands for radial – meaning the layers of rubber used to make the tire are laid radially.
Wheel Diameter: 16
The wheel diameter is 16 inches. This tire is made to be mounted on a 16” wheel (rim).
How to read a tire measured in inches – 31x10.50R15LT E
Diameter: 31
The total diameter of the tire (from top to bottom). In this case, it’s 31 inches.
Section Width: 10.50
The section width is the width of the tread from sidewall to sidewall. In this example, it’s 10.50 inches.
Wheel Diameter: 15
The wheel diameter is 15 inches. This tire is made to be mounted on a 15” wheel (rim).
Tire Class: LT
The tire class for this tire is “LT” which means it’s a light truck. “P” stands for passenger, and “ST” is for trailer tires.
Load Range: E
“E” designates a 10-ply sidewall. “D” is 8-ply, “C” is 6-ply, and “B” is 4-ply.
To learn about speed rating and load index, check out our article.
SL 2017
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