Deciphering sidewall graffiti: What those tire codes mean

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A handy display that breaks down exactly what all of the numbers and letters on the sidewall of an automobile tire stand for.

How to read the sidewall graffiti (Photo: AMG Australia)

Does the sidewall graffiti on your car’s tires hold the secret to life, the universe and everything? Author Douglas Adams might be intrigued at the notion, but the truth is that tire codes tell consumers about the tire’s size, wear, construction and speed rating, among other things. Using properly sized and rated tires for your vehicle is an important part of getting the most from your vehicle and increasing mpg. Thanks to our friends at Edmunds, here’s your official cheat sheet for breaking down the mystery of the tire codes on your daily commuter or weekend joy-rider. You’ll have that sidewall graffiti figured out in no time and only have to worry about coming to Car Deal Expert the next time you’re in need of auto loans.

Sidewall graffiti: If your tires could talk

Let’s use this tire code as our sample: 205/55R 16 89V. Let’s see how that breaks down:

  • 205 – This is the tire’s section width, which measures the millimeter distance between sidewall edges. The larger the number, the fatter the tire.
  • 55 – The aspect ratio that compares section height to width. In this case, the section (or sidewall) height is 55 percent of the section width. Lower numbers (under 55, for instance) mean a shorter sidewall, which grants improved handling.
  • R – This is the tire’s construction, in this case radial. Radial has been the standard for the past 20 years, but certain trucks still use the same old bias-play construction.
  • 16 ­– In inches, this is the rim diameter. If you want to upgrade your wheels, you’ll need a set of tires to match the new wheel size.
  • 89 – The load index, which is translatable via the Maximum Load-Carrying Capacity Per Tire chart. Here, “89” equates to 1,279 pounds (580 kilograms) per tire. Multiply the result by four to get total weight capacity for a set of tires.
  • V – This is the speed rating, which tells you maximum recommended speed a tire is designed to accept over an extended period of time. “V” means the tire can safely run at up to 149 mph for a period of time. Go over that for too long (say for several minutes) and your tires may explode. For other speed codes, click here.

Other things to consider in your sidewall graffiti

Edmunds suggests that there may be other information, such as a DOT (Department of Transportation) number that helps the DOT track production numbers in the case of a recall. A traction rating of A, B or C may also be found, with “A” being the best. The term “TREADWEAR” may also be visible among the tire codes, alongside a number like 120 or 180. The industry standard is 100, so a tire with a 180 is designed to maintain acceptable tread for traction 80 percent longer than the industry standard. Other scales may be used, but in general, if the number is high rather than low, tread life will be longer.

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