1) Sidewall Bubbles. Do you see big or little bubbles in your tires' sidewalls? Then you’re definitely in need of new tires. Sidewall bubbles indicate a serious internal problem for your tire and can cause sudden tire failure, especially at high speeds.
2) Failed the Penny Test. The penny test is one of the most famous - and easiest - ways to know if you need new tires. All you have to do is take a penny, with Lincoln upside down, and place it in the tread of your tire. If you can see the top of the president’s head, your tread is too worn out, making the tire less safe.
3) Visible Wear Bars. Tire “wear bars” might be slightly less well-known than the penny test, but they’re a great way to determine if your tread is too low. Simply examine your tires closely, if you see the bars are aligned with your tires’ tread, you need a new set.
4) Road Vibrations. Unless you’re driving over gravel or cobblestone, your car shouldn’t vibrate. That’s why it’s imperative to bring your car in for service if you are feeling lots of shaking or vibration while driving. Normally, this will be due to poor tire alignment, but if you still feel shaking, your tires may be out of whack too.