Great detailed explanation!

Originally posted by Heraclid
Take this example:
P205/70R16 89S


The "P" stands for "P-Metric" or "Passenger". This means that it is a North American tire sizing designation.

The "205" is the width of a tire, also known as the "section width". This is the width of the tire in millimeters at its widest point.

The "70"is known as the Aspect Ratio. It is calculated by dividing the section height by the section width and multiplying by 100.


The "R" stands for Radial, meaning it has a radial construction.

The "15" stands for the diameter of the wheel in inches.

The "89" is a load rating for this tire.

The "S" is a speed rating for the tire.