Determining the Age of a Tyre
When it comes to determining the age of a tyre, it is easy to identify when a tyre was manufactured by reading its Tyre Identification Number (often referred to as the tire's serial number). Unlike vehicle identification numbers (VINs) and the serial numbers used on many other consumer goods (which identify one specific item), Tyre Identification Numbers are really batch codes that identify the week and year the tyre was produced.
The U.S. Department of Transportation (DOT) National Highway Traffic Safety Administration (NHTSA) requires that Tyre Identification Numbers be a combination of the letters DOT, followed by ten, eleven or twelve letters and/or numbers that identify the manufacturing location, tyre size and manufacturer's code, along with the week and year the tyre was manufactured.
"When it comes to determining the age of a tyre, it is easy to identify when a tyre was manufactured by reading its Tyre Identification Number (often referred to as the tyre's serial number)."
Tyres Manufactured Since 2000
Since 2000, the week and year the tyre was produced has been provided by the last four digits of the Tyre Identification Number with the 2 digits being used to identify the week immediately preceding the 2 digits used to identify the year.
Example of a tyre manufactured since 2000 with the current Tyre Identification Number format:
|In the example above:|
|DOT U2LL LMLR 5107|
While the entire Tyre Identification Number is required to be branded onto one sidewall of every tyre, current regulations also require that DOT and the first digits of the Tyre Identification Number must also be branded onto the opposite sidewall. Therefore, it is possible to see a Tyre Identification Number that appears incomplete and requires looking at the tyre's other sidewall to find the entire Tyre Identification Number.
The use of a partial Tyre Identification Number on the one sidewall (shown above) reduces the risk of injury to the mold technician that would have to install the weekly date code on the top sidewall portion of a hot tyre mold.
Tyres Manufactured Before 2000
The Tyre Identification Number for tyres produced prior to 2000 was based on the assumption that tyres would not be in service for ten years. While they were required to provide the same information as today's tyres, the week and year the tyre was produced was contained in the last three digits. The 2 digits used to identify the week a tyre was manufactured immediately preceded asingle digit used to identify the year.
Example of a tyre manufactured before 2000 with the earlier Tyre Identification Number format:
|In the example above:|
|DOT EJ8J DFM 408|
|40||Manufactured during the 40th week of the year|
|8||Manufactured during the 8th year of the decade|
While the previous Tyre Identification Number format identified that a tyre was built in the 8th year of a decade, there was no universal identifier that confirmed which decade (tyres produced in the 1990s may have a small triangle following the Tyre Identification Number to identify the decade).
And finally, hold on to your sales receipt. Most tire manufacturer's warranties cover their tyres for four years from the date of purchase or five years from the week the tires were manufactured. So if you purchase new tyres that were manufactured exactly two years ago they will be covered for a total of six years (four years from the date of purchase) as long as you have your receipt. If you lose your receipt, your tyres' warranty coverage will end five years from the week the tire was produced (resulting in the tire manufacturer's warranty coverage ending only three years from the date of purchase in this example).