The purpose of the tread on your tires is to divert water from underneath the tire in order to improve traction and prevent hydroplaning. As the tires wear down, they become unsafe to drive on.
To determine if you need new tires, first take a look at the tread pattern. Tires sold in the United States have a feature called tread wear bars. These bars are small, rubber bridges that form between the treads of the tire. The treads will be more raised than the bars but over time, as the tires wear down, the bars will become flush with the treads. This means it’s time to replace those tires.
You can also check the treads by doing what’s called the “penny test.” To do this, take a penny and insert it into the center of the tread with Lincoln’s head facing down. If you can still see the top of Lincoln’s head, then immediately replace your tires. If you can’t see the hair on his head, then your tires are good for now.
It’s also a good idea to check for irregular or uneven tread wear. Over inflation can cause the center of the tread to wear more whereas under inflation can cause excessive wear on the shoulders. If the tread is uneven, this may be an indication of poor wheel alignment. If one side of the tire has more wear than the other, the camber angle may be incorrect.