The tire birth certificate
First of all, every car tire has a kind of birth certificate on its side, which can be used to find out the age of the tyre. This so-called DOT number (DOT = Department of Transportation) must be found on the sidewall of the tire. The corresponding number consists of four digits and is surrounded by an oval circle. If “3716” is there, it means nothing other than that the tire was produced in the 37th calendar week of 2016.
When does a tire change make sense?
If the tread depth is less than 1.6 millimeters, you must change the tire, no matter how old it is. But even if the penalties only apply at 1.6 millimeters remaining tread, you should already change the tires when the tread is around 3.0 millimeters, because then cornering and braking potential decrease significantly.