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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.
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...
Tire Size Explained: Reading the Sidewall. Tire size can be confusing. Some numbers on the sidewall are listed in metric while others are in inches. Plus, the right size for your car, truck or trailer can differ depending on tire use and your driving habits.
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.
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 Explanation. You are one step away from getting a detailed, color-coded explanation of a specific tire code. Just click on a size below to get a break down of what it means.
Tire Sizes Explained Section width of tire (Example: P 225 /45R17 91V) The three digits following the service type prefix (if present) tell us the cross-sectional width of the tire 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
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.
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.