View Here : Tire Size Meaning
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.
Finding the tire size meaning in metric measurements is a little more difficult and usually take a calculator to get exactly right. Example B : 305/70R17 On metric tires the first number is your width of the tire in millimeters. In example "B" this reads 305mm. There are 25.4 mm in one inch.
If the tire size begins with a T, it means that the tire is a temporary spare. Also known as mini spares or space savers, temporary spares are designed for short-term use until the regular tire is repaired or replaced.
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. Aspect Ratio 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.
The tire size branded on the sidewall provides a significant amount of information about the tire's intended purpose, dimensions, load capacity and high temperature/high speed durability. Our primary example will be based on variations of the 225/50R16 size, although other sizes will appear...
A tire size calculator is a quick way to see whether the tire size you’re considering will likely fit your car, SUV, sports car, light truck or crossover. But remember that will give you just an estimate.
If your tire size starts with LT rather than a P than it identifies the tire as a Light Truck tire. 225 identifies the tire section width, which is the measurement of the tire from sidewall to sidewall in millimeters.
P designates this tire as a passenger car tire, an LT before the tire size would mean the tire is a light truck tire, and a European metric tire would have no letter before the tire size. 245 = Section Width
Tire size was specified as the tire width in inches and the diameter in inches - for example 6.50-15.  From 1965 to the early 70's, tires were made to an 80% aspect ratio.
A tire has a Series Size System when the aspect ratio is unspecified, so it will always be 82% unless it is specifically noted to have an 85% aspect ratio. However, manufacturers are no longer using tires with this size system, so you are unlikely to find tires marked this way.