How do you read tire size?

Let's use the example of the very common P185/65R14/ 85S: P= this designates the tire a following "Passenger Metric" load and inflation tables. Some tires will use the European Metric tables and and will not have a P in the description. A tire size built sin the European system would be like this 185/65R14 86S. 185= the "Section Width" or width of the tire at it's widest point in millimeters. This is not the width of the tread. 65= the "Section Height" or how high the tire is measured from the bead to the top of the tread, represented as a percentage of the "section width". In other words, 65% of 185mm. R= This means the tire is radial construction. 14= the diameter of the wheel the tire can be mounted on measured in inches. Yes tire sizes mix metric and English measurements. 85S= This is the "Service Description" which is frequently ignored but critically important. It gives two different bits of information. The "85" is the "load index" and tells us how much weight (load) the tire can support at specific inflation pressures and the maximum load, which on a passenger metric standard load tire peaks at 35 psi. The "S" is the "speed rating" and indicates the speed the tire is built to sustain under specific test conditions. The S equates to 112mph.