How to Read Tire Sizes

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To read tire sizes break down the full number that appears on the tire by the tire type, tire tread width, aspect ratio, rim size and load rating. Determine the size of various types of tires with instructions from an ASE-certified technician in this free video on tires.

Part of the Video Series: Driving Lessons & Tire Care
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Video Transcript

All right, in this clip we're going to teach you how to read your tire sizes; that is, how to translate what these tire sizes actually mean. In this particular case, this tire is a P265/65R17. The P, the first letter, actually means passenger tire. In the consumer world there's about two different ratings you're going to be dealing with on a daily basis. One is P, meaning passenger tire. The other one is LT, meaning light truck tires. You'll usually see those on heavier trucks, or heavier SUV's that require a higher load rating. The second number, 265, is actually the measurement of how wide the tread on the tire is in millimeters, so this particular tire is actually 265 millimeters wide for the tread. After the slash the third thing you're going to be dealing with, the 65, is actually called the aspect ratio. That means that this tire is 65 percent as tall as it is wide, so it's actually 65 percent of the 265 millimeters. The third rating, the R17, actually men means the rim size, so this particular rim is a 17 inch rim. The last two numbers you're going to be dealing with, the 110T, the 110 is actually the load rating of the tire, and the T is actually the speed rating of the tire. So, all tires are going to be read in this order, P or LT, and then a measurement of the millimeters in the size of the tread. Third number, aspect ratio; how tall the tire is compared to how wide it is. The rim size, then the load rating, then the speed rating.


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