The U.S. Department of Transportation--DOT--dictates what information must be provided on the sidewall of any tire sold for road use in the United States. With a little detective work and an understanding of the DOT coding system, you can determine the age of any motorcycle tire.
Locate the full DOT number on the sidewall of the tire. The number starts with "DOT" and is followed by 10 to 12 letters and numbers. The full DOT number is only on the outside of the tire. The inside will have a shortened version with just a few letters or numbers.
Note the last four digits of the DOT number. They will all be numerals, such as 2708 or 0510.
These numbers let you decode the date of manufacture of the tire. The first two numbers indicate the week; the last two the year. For example, 0510 indicates the tire was produced in the fifth week of 2010.
Subtract the tire manufacture date from the current date to determine the tyre's age. To get the month of manufacture, divide the weeks by 4.3. If it is October 2010 and the tire was manufactured in the twenty-fifth week of 2008, the tyre's production month was June, making the tire two years and four months old.
Tires manufactured before the year 2000 may have a three-digit manufacture date with a single digit for the year. When dividing by 4.3, the month of manufacture is the next whole number. For example, 25 divided by 4.3 is 5.814, so the month would the sixth month--June.
Motorcycle tires are covered by a factory warranty for five or six years. Tires older than six years should not be used even if they appear to be in good condition. Older tires can develop dry rot and unseen structural damage.