.........since tires is just about the only thing I know about..........Please drop me a note if you have a topic you want to see: [email protected] Tire Update April 2015: NHTSA (National Highway and Traffic Safety Administration), the branch of the US government that regulates tires (and in this case, what is required to appear on the sidewall), has annouced that they have run out of 2 digit plant codes (see below) and are making a change to a 3 digit plant code.So from April, 2015 to April, 2025, you will see both 2 digit and 3 digit plant codes - and the existing plant codes COULD use a "1" (One) in front. If you look to the right, the plant code for the DOT number would be 5M.Here's a web site that has an old version of the plant codes: From time to time, this gets updated, but don't depend on this being 100% right.This is a series of articles on the technical aspects of tires, their care and usage.My primary purpose in these articles is to help people understand tires and thereby reduce the risks we all face every day.Look on the outer sidewall for the acronym “DOT,” which should be followed by a series of numbers.The last four digits are what you need to determine when the tire was manufactured.
The coding is optional, but since many tire manufacturers use the code to track returns, I don't know of anyone who doesn't use this coding.
The rule of thumb is to replace tires when they are 6 years old, even if they appear to be in good condition.
This is because the rubber can develop dry rot and other structural damage that you may not be able to see.
Also, there are different types of tires that require DOT coding.
This lists only addresses Passenger, Truck, and Motorcycle tires (3 separate lists!
To make the transition easier, NHTSA has reserved a series of 3 digits codes starting with the number "1" (One) followed by the previous 2 digit codes.