The letter “P” at the beginning of the “Tire Size” tells us the tire is a P-Metric tire, referring to tires made to certain standards intended for Passenger vehicles.
If a tire size has no letters at the beginning, this indicates a Euro metric tire. P-Metric and Euro-Metric tires may have different load capacities.
The letters “LT,” either at the beginning or at the end of the tire size indicate the tire was designed for light trucks. Vehicle manufacturers equip some light trucks with “LT” type tires. These tires generally require higher inflation pressures than passenger tires.
Consult your owner’s manual or tire placard for the recommended tire size and inflation pressure for your vehicle.
Is the width of the tire measured in millimeters from sidewall to sidewall. The first three-digit number in the tire size refers to the tire width. For instance, in a size P215/65 R15 tire, the width is 215 millimeters.
Is the ratio of the height of the tire’s cross-section to its width. The two-digit number after the slash mark in a tire size is the aspect ratio. For example, in a size P215/65 R15 tire, the 65 means that the height is equal to 65% of the tire’s width. The bigger the aspect ratio, the bigger the tire’s sidewall will be.
The letter “R” in a tire size stands for Radial, which means the layers run radially across the tire.
Is the size of the wheel measured from one end to the other. It tells us the size of the wheel that the tire is intended to fit. A size P215/65 R15 tire is made for a wheel with a 15″ diameter.