What do tire measurements mean?

Tire measurements mean a few different things. First we will look at a certain tire size, such as P235/75R15...the size of our truck tires. The P means P-metric, or referring to passenger vehicles. The next number means the measurement in millimeters of the tire from the outer sidewall to the inner sidewall when it is mounted on a rim. The 75 in this case refers to the sidewall height from the rim to the tread. The R means it is a tire made by radial construction, and the 15 means rim size diameter in inches.