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How to Read a Tire's Sidewall Codes

Last updated 6 years ago

Sidewall codes are full of information about the right tire for your vehicle. Check these codes before purchasing replacements and ensure your new wheels are a perfect fit.

  • Tire Dimensions: The section of tire code that describes the tire’s size begins with the letter “P” or “LT.” These symbols are used to indicate the tire’s class. “P” tires are designed for passenger cars. “LT” tires are developed with light trucks in mind. This lettering is followed by a three digit number indicating section width. This value is measured in millimeters. The following two digit number is an aspect ratio used to determine the height of the tire. Next in sequence is a letter used to designate tire construction type. The final component in this series is a two digit number that reports tire diameter in inches.
  • Performance Parameters: The symbol series directly following the tire dimension code communicates the load and speed capabilities of the tire. The first symbol is a one to three digit load index. This number measures the tire’s load capacity on a scale from 0 (supporting up to 99 lbs.) to 279 (supporting up to 7385 lbs.). Typical tires range in load capacity between 75 and 105. Load capacity is followed by a speed rating. This symbol reflects U.S. Government standards for safe driving at elevated speeds. Speed ratings run the gamut from Q (sufficient up to 100 mph) to Z (the standard for speeds above 150 mph).
  • Manufacturer Information: Your tire code also includes data relating to its origin and build. This sequence begins with a “DOT” marking from the U.S. Department of Transportation. This designation also indicates that the tire has met government safety standards for performance on the road. Two letters follow the Department of Transportation mark. These letters represent the plant where the tire was produced. Next, a number-letter combination describes the tire’s size. The final seven or eight digits differ a bit between manufacturers, but generally describe brand features and manufacturing date.

Call Dekalb Tire today at (404) 252-9895 if you have more questions about  sidewall codes or tires in general. 


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