Tire Sidewall Markings: What the Numbers and Letters Mean

tire sidewall markingsCar tires have all sorts of numbers and letters inscribed on them. Some are self-explanatory, such as the indicated max psi and max capacity load. However, other tire sidewall markings are more obscure. The average car owner probably has no clue what a marking like LT285/70R17 means. We’ll explain what these numbers and letters tell you about your tire. Our auto service works with tires all the time, and discerning these markings are second-nature to us.

What the Tire Sidewall Markings Mean

Common markings may include ones like the following:

  • LT285/70R17
  • P205/60R15
  • ST205/75D15

The beginning letter includes one of these three: LT, P, and ST. These letters stand for:

  • LT – light truck
  • P – passenger vehicle
  • ST – special trailer

The first three digits after the letter indicates the width in millimeters, measured from one face of the sidewall to the other. The two digits that come after the slash represents the aspect ratio for determining the height of the sidewall. With LT285/70R17, for example, the sidewall height is 70% of 285, or 199.5 millimeters.

After the aspect ratio, you may see another letter followed by a final two-digit number. The letters indicate the construction of the fabric carcass of the tire:

  • R—radial: has steel cords on the heel of the tire and a belt across the carcass
  • D—diagonal: has multiple carcass layers placed diagonally across each other
  • B—bias belt: is constructed from multiple nylon belts running at 30-45 degree angles

The two-digit number that comes after represents the wheel diameter, in inches, that the tire will fit.

Don’t Mind the Sidewall Markings

Bring your car to Avery Automotive and let us worry about the markings. They’re primarily for an auto repair professional’s reference, anyways. Our repair financing often includes tire-related services. The tire sidewall markings ensure repairs and replacements are done to industry standards.

Edited by Justin Vorhees

Tire Services Ranging from Replacement to Alignment

Serving customers in Gold Bar, Index, Maltby, Monroe, Skykomish, Snohomish, Startup, and Sultan