The alphanumeric code on the side of a tire looks more like something out of da Vinci’s codex than product labeling. Tire nerds can translate the rubber cypher; read this and you can join their ranks.

SIZE

This sequence can be preceded by a P (for P-metric, generally used on passenger vehicles), LT (light-truck metric), or T (temporary spare). No letter means that the tire was engineered using Euro-metric standards. The prefix means little for the end user, and P, non-P, and LT tires are interchangeable, though LT tires generally have higher load ratings (see service description) and are designed to use higher inflation pressures. The three-digit number is the tire’s section width in millimeters followed by the aspect ratio: sidewall height divided by section width. The following letter(s) describe the construction: R is for radial; ZR stands for a Z-rated radial (see service description); and ZRF means Z-rated run-flat (rare). The last two-digit number is the diameter of the applicable wheel, in inches.

DOT COMPLIANCE CODE

The week in which a tire is manufactured is marked in the last four digits of the DOT compliance code. For example, a tire built on New Year’s Eve 2011 would be marked “5211.” The rest of the code is essentially meaningless to consumers.

ORIGINAL EQUIPMENT FITMENTS

These vary by manufacturer, but the marking indicates that a tire is designed specifically for a particular car. Tire compounding, construction, or both could be different from the standard tire. N0, N1, N2, N3, N4 = Porsche. 5-pointed star = BMW. M0 = Mercedes. K1 = Ferrari, obviously. TPC SPEC = GM; only slightly more obvious than Ferrari.

SNOWFLAKE IN A MOUNTAIN

This pictogram indicates that a tire meets the packed-snow-traction requirements set by the U.S. Rubber Manufacturing Association and the Rubber Association of Canada.

M+S

This marking may appear as MS, M/S, M&S, or M+S. This stands for “mud and snow,” determined by the amount of void (sipes and grooves) in the tread.

UNIFORM TIRE QUALITY GUIDE STANDARD

Commonly referred to as the UTQG, this is a standardized wear and traction rating. It is mandatory for all tires sold in the States. A higher number indicates that the tire should last longer than a tire with a lower number. The letters following indicate relative traction and temperature grades: An A is better than a B, etc. Think of this as EPA ratings for tires—a standard test that provides consumers nothing but a rough guideline.

SERVICE DESCRIPTION

This defines the capabilities of a tire. The two- or three-digit number is a load rating. The higher the number, the higher the load—or weight—this tire is rated to carry. The letter is a speed rating. At the low end, an L indicates that a tire is rated for 75 mph, though most new cars come on S-rated tires (112 mph) or higher. Z-rated tires are designed to go faster than 149 mph. As top speeds have climbed over the past three decades, manufacturers wanted something more specific, which led to the introduction of W- (168 mph) and Y- (186 mph) rated tires. If a W- or Y-rated tire’s service description is in parentheses, that means the tire is rated for speeds greater than 168 and 186, respectively. Because W and Y tires are rated for more than 149 mph, they are also Z-rated, though this marking is sometimes omitted in the size.

DON'T IGNORE THE FINE PRINT

Tire stickers are normally discarded, but our Toyos and Yokohamas came with an additional warning that grabbed our attention. Both instruct owners not to store, use, or expose these tires in extremely low temperatures—below 15 degrees F for the Toyo, 14 degrees for the Yoko. These tires are subject to a phenomenon known as cold compound cracking, which happens when the tire’s temperature drops below the glass-transition point of the compound and the rubber is subjected to even modest flexing. Rogers gives a great analogy: “A Snickers bar flexes easily at room temperature. Put it in the freezer for an hour, and you can shatter it upon impact against a countertop. The same phenomenon applies here.”

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io