Tire Sidewall Markings

One of the most confusing parts about buying new tires is deciphering the code on the sidewall. With the guidelines below, you can easily figure out what kind of tire currently is fitted to your vehicle.

Example of tire sidewall markings –LT305/70R17,M+S, Load Range D

  • The first letter indicates the type of tire your car is sporting. P=Passenger, LT=Light Truck, UHP= Ultra-High Performance, etc.  These are use to indicate what the tire is used for (every-day driving, hauling, handling and so on). 
  • Following this is a three-digit code, which refers to the tire’s overall width of the tire in millimeters.
  • The three-digits are followed be a two-digit number that defines tire's aspect ratio. The aspect ratio is relationship between your tire’s height and width. In the example here, the height is 65% of the width.
  • The letter "R" indicates radial tire. This letter marking can be found on almost all tires with unless you are purchasing those used on antique or classic cars.
  • The two-digit number after the “R” is the wheel diameter the tire is intended to fit. In this case it is 17” wheel. 
  • The "M+S" or "M/S" letters shown on the tires stand for mud and snow and applies to standard vehicle tires sold in the United States.
  • Finally, the Load Range “D” in the tire image indicates the tire’s ply rating, or how much the tire can carry at a certain inflation pressure.  A simple way to identify this is to take the number associated with the letter and multiply it by 2. See the chart below. 

Load Ranges Ply Ratings Load Pressure (PSI)
B 4 35
C 6 50
D 8 65
E 10 80
F 12 95

Additional information about the tire sidewall reading can be found on the National Highway Traffic Safety Administration’s website.

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