Dot Tire Identification Codes
All new tires sold in the United States must have a DOT number cured into the lower sidewall of one side of the tire. This code has a standard format which has been designated by the federal government.
Some manufacturers place an additional code with a specific serial, which identifies the specific tire model (a tire type code). This optional number is located on the sidewall opposite the DOT number.
Commercial treads also include codes, which are used to detail retread information. This code is generally found on the lower sidewall near the original DOT code.
SIZE DESIGNATION AND SERVICE DESCRIPTION
There are many factors that contribute to how your vehicle performs, but few have as direct an impact as its tires. It’s vital to have a good understanding of your tires’ capabilities, and more importantly, their limitations. A tire’s weight and speed limits are indicated by the tire service description; a short code located on the sidewall. This short code, which consists of a two- or three-digit number along with a single letter, designates just how much weight your tires are capable of carrying safely (load index) and the maximum speed the tires are designed for (speed category).