What’s in a tire code?
Most people think of a tire as a tire. Many don’t even bother to look at the data on the side of their new rubbery friend that gives them more information about what they’re buying. Reading tire codes is easy once the buyer is aware of the different symbols that manufacturers engrave on the sidewall sections. With a little knowledge, the average person can become an expert in no time.
What is a tire code?
Tire codes provide new tire buyers with a wealth of information. Tire manufacturer, type of material, dimensions and maximum speed allowed are just some of the quick reference data that tire codes offer to interested buyers. The codes are universal and offer the same information for all consumers. Over the years, the codes have become more complicated due to advancing technologies in tire manufacturing. Tire codes always use the standard metric system for measurement, which, believe it or not, most Americans have subconsciously become accustomed to.
vehicle rating
The first letter in any tire code determines the type of vehicle the tire supports. In the example, P215/65R15, the “P” stands for passenger car. Tire manufacturers would use an “LT” to show the tire is compatible with light trucks, an “ST” for specialty trailers, and a “T” for temporary or spare tires.
width and height
The next set of digits, 215/65, represents a tire’s aspect ratio in millimeters. The 215 is the width of the tire with 65 symbolizing its height, as a percentage of width. A 215/65 tire is 140mm tall or 65% of 215 (215x 0.65).
Construction type and diameter
Some tires carry additional information to help buyers quickly find the type of tire they are looking for. The letters after the rating and dimension data specify the tire design with “R” standing for radial, “B” for belt bias, and “D” indicating diagonal bias. The number that follows the type of construction of a tire indicates its radius. Therefore, an “R15” tire is a radial tire with a diameter of 15 inches wide.
cargo information
Each new tire specifies the maximum weight it can support when inflated. Manufacturers write this information directly on the tire. However, some manufacturers use a code to display their maximum load, using a number taken from the European Tire and Rim Technical Organization (ETRTO). ETRTO load codes range from 60 to 125, indicating maximum loads from 250 kg (550 lb) to 1,650 kg (3,600 lb). The maximum load information of a tire is especially important for trailers or trailers that carry heavy loads.
speed ratings
This rating is also marked on each tire and is sometimes combined with load information. The speed rating code informs drivers of the maximum speed the tire can handle with the maximum load. In the example, P215/65R15 87L, the 87 is the ETRTO load code and the “L” is the speed rating of the tire, taken from the ETRTO speed rating table. These ratings range from “A1” (3 mph/5 km/h) to “Y” (186 mph/300 km/h). An “H” rating has a top speed of 130 mph or 210 km/h with maximum load.
Road condition markers
Winter and summer storm tires are very popular in today’s market for those customers who live in places with extreme weather. Sometimes tires can have special characters marked on them, telling buyers how they perform under certain weather conditions. Road condition indicators can range from simple snowflake drawings on the tire to letter symbols, such as M+S, that stand for mud and snow.
DOT Number
Most tires sold in Europe, the US and Canada have a Department of Transportation (DOT) number marked on their sidewall. This number provides a quick reference to the tire manufacturer, plant number, batch and production date for anyone interested.
Knowing how to read tire codes can help buyers find the perfect match for their car. Being prepared before entering a tire store improves communication and helps tire suppliers choose the best product to make a consumer’s vehicle the safest on the road.
