From my friend and fellow lawyer Rob Bunch, this article:
With all of the information contained on a tire’s sidewall, it’s no wonder the average consumer has difficulty deciphering it all. While most know how to tell a tire’s size and width, the manufacturer, and the maximum inflation pressure, the tire’s DOT serial numbering system may not be so easy to understand. A tire’s DOT number contains valuable information, especially when a tire was manufactured, but it was never meant to be very consumer friendly and was never meant to be decoded by the consumer. Having the means to tell when a tire was manufactured can mean the difference between safety and catastrophic results.
Some experts believe that tires have a shelf life and ignoring that could be fatal. Tires can sit on store shelves for years before they are sold; sometimes as long as five years; each can still be sold as new tires. There is no expiration date on tires, but research and tests show as tires get older, even if they haven’t even been driven a mile, the tires may begin to dry out, and the degradation process starts to take place.
After six years of age, tires can become unreliable or even dangerous. Tires may look great on the outside, but not much is known about what is going on inside the tire. After a time, tires begin to dry out and become less elastic even if they are not in use, making tread separation more likely even if they have plenty of tread depth and appear new. When a tire detreads at highway speeds, it becomes difficult if not impossible to retain control of a vehicle.
For decades, the tire industry has taught drivers to use the so-called “penny test” as a way to tell when a tire needed to be replaced. As late as last summer, they have recommended that the “penny test” is outdated, compromises safety, and should give way to the “quarter test.” Why not arm consumers with the knowledge of determining when their tires were manufactured by decoding the DOT serial number and then recommend that they replace them at a certain age, no matter what the tread depth? Or better yet, why not imprint an expiration date on the tires?
The U.S. tire industry has fought efforts to require an expiration date on tires. The industry says, given the improvements in tire production, age is not a key factor in a tire’s performance. However, the British Rubber Manufacturer’s Association issued a forceful warning to its British consumers stating “BRMA members strongly recommend that unused tires should not be put into service if they are over 6 years old . . .”. This is something that would come as news to most U.S. car owners, but seems to be known by everyone but the American consumer. In fact, the head of the U.S. Rubber Manufacturers Association has gone on record saying that there is no need for U.S. drivers to be given the same warning that British car owners have received.
U. S. car manufacturers have been warning their customers for years about the problems with aging tires. In fact, Ford Motor Company has asked the federal government to impose a 6 year age limit or expiration on tires.
So just how do you tell when your tires were manufactured? Begin by locating the DOT number on the sidewall of your tire. Up until last year, the DOT number was molded on the inside of tires, making it extremely difficult to locate. To read it, the consumer either had to put their vehicle on a lift or crawl under it with a flashlight to find it. Once you have located your DOT number, identify the 3 or 4 numbers at the very end of the serial number. If a tire has three numbers, it means that the tire was made prior to January 2000. If a tire has four numbers, it indicates that the tire was manufactured after January 1, 2000. The first two numbers in the date of manufacture indicate the week in which the tire was made.
I your tire has 036 as the last three digits of your DOT number, it indicates that the tire was manufactured in the third week of 1996. If your tire has 4604 as the last four digits of your DOT number, it indicates the tire was manufactured in the 46th week of 2004. Experts urge motorists to check their tires’ manufacturing date and replace them after six years of age.