How do I know if my tires are too old, even if they still have tread?

Check the DOT code on the tire’s sidewall. The last four digits show the week and year it was made, so “2321” means the 23rd week of 2021. Most experts recommend replacing tires after 5 to 6 years regardless of tread, because the rubber hardens and can crack. Look out for cracks, bulges, or uneven wear too.