View Here : Tire Size Meaning
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.
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.
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 letter "R" in a tire size stands for Radial, which means the layers run radially across the tire. Wheel Diameter 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.
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.
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.
Prior to 1964, tires were all made to a 90% aspect ratio. 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. Tire size was again specified by width in inches and diameter in inches.
Tire load index is an assigned number that corresponds to the maximum weight that a tire can support when properly inflated. The higher the tire's load index number, the greater its load carrying capacity.
Road touring and racing tires: On road bike tires, you'll see a number pairing such as 700x23. The first number (700) is a size that roughly corresponds to the outer diameter of the tire in millimeters.