Just because your car or truck came with 4 new or used tires does not mean that you can’t switch them up. There are lots of things that you can do with your tires to increase the performance of your car. The 1st number is the width of the tire in millimeters when its fully mounted on the rim but BEFORE you put it on your used car or truck.
For all tires built after 1999, this will be a four-digit number with the first two digits giving the week number, and the last two giving the year. For many tires built previous to 2000, the date indicator will consist of three digits, the first two giving the week number and the last giving the last digit of the year.