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.
ST = If a tire size begins with "ST," it signifies the tire is a "Special Trailer Service" size that was designed to only be used on boat, car or utility trailers. ST-sized tires should never be used on cars, vans or light trucks.
Tire Type 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 within the United States, intended for Passenger vehicles.
The tire size "P225/45R17 91V" may not mean much to the average person, but to tire geeks like us it speaks volumes. Read on to learn how to crack the tire code with this handy guide dedicated to tire types, sizes, and construction.
It has either a 17- or 18-inch staggered tire size, meaning a different size front-to-rear. Many opt for a value-oriented Kumho tire. In the 17-inch sizes, the Kumho Solus KH16 is popular and in the 18-inch size it's the Kumho Ecsta STX KL12.
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 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.