What Do the Numbers on Tires Mean?

January 17, 2019

numbers on the tire

If you take a look at your tire’s sidewall, you’ll likely come across a slew of numbers (and perhaps a few letters) that are seemingly out of order and don’t seem to fit. On first glance, you might think that this is nothing more than an embedded barcode or some sort of identifier to help with the specific tire manufacturer’s quality control. While we don’t put it past you for thinking this, each number (and letter) that appears on the sidewall is an indicator of some piece of key information. On that note, we thought it fitting to debunk this number and tell you exactly what it means. We’ll start with the letter farthest to the left:

P, LT = Tire Type

There’s a very good chance that your tires will begin with either a “P” or the letters “LT.” This is an indicator of tire type. “P” stands for a P-metric tire, which means that the specific tire conforms to the standards of tires made in the United States. The “P” also means that the specific tire is designated for passenger vehicles, like sedans and SUVs. If your tire starts with an “LT” then it means it’s intended for light duty vehicles. While the “LT” most commonly comes at the beginning of the tire, it may also be placed at the end. You may also find “ST” on the tire, which stands for “special trailer.”

If your tire is void of any letter(s) at the beginning of the sequence, then it’s likely because it’s a Euro-metric tire.

The First Three-Digit Number = Width

Following the letters to kick things off (or the lack thereof in the case of a Euro-metric tire) comes the tire width measurement. This is always the first three-digit number on the tire, and it indicates the number of millimeters from the tire’s one sidewall to its other one. So, for example, if your tire reads “P 205,” then you have a P-metric tire intended for passenger vehicles with a 205 millimeter tire width.

The Next Two-Digit Number = Aspect Ratio

Aspect ratio is defined as the ratio at the height of the cross-section to tire width. You can check the aspect ratio by looking for the first two-digit number on the sidewall, which comes after the tire type and the three-digit width measurement. So if you have a tire that reads “P 205/70 R” the aspect ratio is 70, which means the height is 70 percent of the tire’s width.

Construction Type

 You may have noticed from our example above that the tire sidewall reads “P 205/70 R.” That “R” designates the tire construction. In this case, it stands for “radial.” This is considered the industry standard for nearly all tires made today, though you may see a “D” for diagonal plies or “F” for run-flat tires.

Second Two-Digit Number = Wheel Diameter

 The second two-digit number that you’ll find accompanying the construction type is used to define wheel diameter. Wheel diameter is simply the size of the wheel from one end to the other. So if you see “R 15,” for example, the tire’s width is 15 inches.

Third Two- (or Sometimes Three-) Digit Number = Load Index

 The third two- or three-digit number you’ll find on the tire’s sidewall is the load index. This basically indicates how much weight the tire is able to support, and you’ll need to check a corresponding chart to get that weight limit. For example, tires with a load index of 65 can support 639 pounds. Tires with a load index of 100 can support 1,764 pounds. Load index numbers range from 65 to 150.

Last Digit = Speed Rating

Finally, the last digit on most tires is a speed rating indicator. In other words, it’s a suggested top speed to safely travel at for sustained periods of time. Speed ratings for passenger car tires vary, but usually are ether H (130 miles per hour) or V (139 miles per hour). Though rare, speed ratings can be symbols (A1-A8 and 3 mph to 25 mph, respectively). The highest speed rating is designated by a “Y,” which indicates a tire that can support speeds of more than 186 miles per hour.

Hypothetically, let’s say we have a tire sidewall that reads like this: P 205/65 R 15 80 H. Here’s what each letter and number means:

  • P: P-metric, passenger vehicle tire
  • 205: tire width, in millimeters
  • 65: tire aspect ratio
  • R: radial construction type
  • 15: wheel diameter, in inches
  • 80: load index, indicating a tire that can support 992 pounds
  • H: speed rating, indicating a tire that travel at a 130 mph sustained top speed.

For more information on about tires, new or replacements, check out our selection of products available, be sure to contact HD Wheels or visit www.HDWheelsUSA.com.

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