Tire Sidewalls, Decoded.

December 4th, 2015 by

Ever wonder what those markings on your tire mean? Decipher them with this slideshow (above), then find each of the terms (below), for even more details.

By Jordan Mendoza

Aspect Ratio:
This two-digit number indicates the tire’s height expressed as a percentage of the section width.

The letters “DOT” indicate that the tire meets or exceeds the U.S. Department of Transportation’s safety standards.

Load Index:
This one- to three-digit number corresponds to the maximum amount of weight a tire can safely carry, ranging from 0 to 279, as indicated below.

Load Range:
Indicates how much load the tire is designed to carry and its inflation limits. LT-Metric Load Ranges differ from P-Metric load ranges (see charts below). Most P-metric passenger tires have a standard load range, so they’ll have nothing branded on the sidewalls or will be identified by SL. Other designations include Light Load and Extra Load. Extra Load tires can use higher air pressure to support more weight than a standard tire of the same size.



Manufacturing Plant ID
This code corresponds to the factory where the tire was made.

Manufacture Week / Year
These numbers indicate the week and year in which week the tire was manufactured.

Marketing Codes
These vary based on the tire manufacturer’s discretion. They may indicate tire size or brand-specific identifiers, and are often used in case of a recall.

Maximum Air Pressure:
Based on standards set by the National Highway Traffic Safety Administration (NHTSA), this indicates the maximum operating inflation pressure.

Maximum Load Limit:
Also based on NHTSA standards, this refers to the tire’s maximum load-carrying capabilities.

Ply Construction:
This is a list of the materials and their quantities used to construct the tire.

Rotation Direction:
Some tires have indicators to show the direction in which they should rotate and/or which side should face outward:

  • Directional tires indicate direction of rotation.
  • Asymmetrical tires indicate which side should face outward.

Section Width:
This three-digit number shows the width of the tire in millimeters, measuring from sidewall to sidewall.

Speed Rating:
This indicates the speed at which a tire can carry a load, corresponding to the Load Index.

Temperature Rating:
This represents the tire’s ability to withstand heat on a scale from A to C, where A runs the coolest (i.e., most resistant to heat generation) and C is the minimum performance required by federal safety standards.

Tire Class:
This marking tells you what type of vehicle the tire is made for.

  • P: Passenger car
  • LT: Light truck
  • ST: Special trailer
  • T: Temporary (restricted usage for “space-saver” spare wheels)
  • No letter: European metric tire

Tire Construction:
This letter relates to the internal construction of the tire. (Most passenger-car tires today are radial.)

  • B: Bias belt
  • D: Diagonal
  • R: Radial
  • No letter: Cross-ply

Traction Rating:
The traction rating shows the tire’s ability to stop on wet pavement under controlled conditions. Grades are: AA (highest), A, B, C.

Treadwear Durability Rating:
This is based on actual road use—a grade of 400 indicates that the tire should last twice as long as a grade of 200. Treadwear grades should be compared within a given brand, because different manufacturers have different grading schemes.

Wheel Diameter:
This is a one- or two-digit number indicating the diameter in inches of the wheel that the tires are designed to fit.


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