According to Federal law, tire manufacturers must permanently brand a series of standardized information onto the sidewalls of all tires sold in the United States. The required data includes information about the tire's basic characteristics, construction, various capacities (load, speed, inflation pressure, etc.) as well as a DOT (Department of Transportation) Tire Identification Number. The DOT number is used for safety standard certification and also in the event of a tire recall by the manufacturer.
According to current regulations, the DOT Tire Identification Number must begin with the letters "DOT" followed by a series of characters (usually 10, 11, or 12 numbers, letters, or symbols). These characters identify the tire size and manufacturer's specifications, as well as the manufacturing location and date the tire was manufactured (listed as week and year). Many people mistakenly refer to the DOT number as a product serial number, but the DOT number is not actually a serial number - rather, it is the identification of the manufacturer's production batches.
If you look at the tire's sidewall and see a DOT number that appears to be incomplete, it is because the current regulations require the entire DOT number to be branded on only one sidewall, while the opposite sidewall is branded with just the first few digits. To see the entire DOT number, simply look on the other sidewall.
If your tire does not have a DOT number branded on its side, then the tire does not meet all U.S. requirements. Not all tires are intended to be imported and sold in the United States, so the tire in question may have been developed and produced without being tested and confirmed by its manufacturer that it has met all U.S. Federal Vehicle Safety Standards (FMVSS). As a result, these tires cannot be legally driven in the United States.
When you purchase new tires, your installer should provide you with a DOT card so that you can record the DOT numbers of your tires and send them to the manufacturer. This information is critical in the event of a tire safety recall. If your installer does not provide you with a DOT card, you may also be able to register online on the manufacturer's website. Most manufacturers provide a link where you can go online and register your DOT numbers.