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 from their new rubber friend’s side that gives them more information on what they are buying. Reading tire codes is easy once the buyer knows 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 buyers of new tires with a wealth of information. Tire manufacturer, material type, dimensions, and maximum allowable speed are just some of the quick reference data that tire codes provide 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 the advancement of technologies in tire manufacturing. Tire codes always use the standard metric system to measure, believe it or not, most Americans have unconsciously got used to it.

Vehicle rating

The first letter in any tire code determines the type of vehicle that the tire supports. In the example, P215 / 65R15, the “P” stands for passenger car. Tire manufacturers would use an “LT” to show that 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 the aspect ratio of a tire in millimeters. The 215 is the width of the tire with 65 symbolizing its height, as a percentage of the width. A 215/65 tire is 140mm high or 65% of 215 (215 x 0.65).

Construction type and diameter

Some tires contain other information to help buyers quickly see what type of tire they are looking for. The letters after the rating and the dimension data specify the tire design with “R” for radial, “B” for belted skew and “D” for diagonal skew. The number following 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.

Loading 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 show 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 for a tire is especially important for trailers or trailers carrying 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 under 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 chart. These ratings range from “A1” (3 mph / 5 kmh) to “Y” (186 mph / 300 kmh). An “H” rating has a top speed of 130 mph or 210 km / h under full load.

Road condition markers

Winter and summer storm tires are very popular on the market today for those customers who live in places with extreme weather conditions. Sometimes tires can be marked with special characters that tell buyers how they perform in certain weather conditions. Road condition indicators can range from simple snowflake patterns on the tire to letter symbols, such as M + S, which 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 the side. This number provides a quick reference to the tire manufacturer, plant number, lot, 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.