Tires are one of the most important parts of your car, but sometimes tire replacement can take you off-guard. There’s nothing like a flat tire on the side of the road to make you realize you haven’t really looked at your tires lately–and maybe you should.

Here are 5 signs that your tires are getting worn out and need to be replaced.

  • The Penny Test

The penny test is the easiest way to check the tread of your tires, and people have been using it for generations. To make sure that your tires have enough tread to provide sufficient traction while driving, simply take a penny and place it in the tread of your tire, head down. If you can see Lincoln’s entire head, you don’t have enough tread.

Since tires can wear unevenly, it’s a good idea to perform the penny test on several places on each tire. It’s also a good idea to get your tires rotated every few months, to prevent your front tires from wearing out before your back ones, or vice versa.

  • Vibrations While Driving

Most tire problems are best diagnosed while your car isn’t moving, but it’s also a good idea to pay attention to your car as you’re driving it. If your car is vibrating a lot when you drive, it may indicate a tire problem. Of course, vibrations can be caused by poor alignment or shocks that need to be replace, but no matter what, a lot of vibration when you’re driving doesn’t mean anything good and you should get it checked out.

If you’re wondering how to tell if your car is vibrating more than usual, try turning everything in your car off–the radio, the heater, the air conditioner, anything that makes noise. Then drive down a paved road without any rough patches and see how your car handles. If it’s a bumpy ride, you may want to go see a mechanic.

  • Tire Damage

Tires can get damaged unexpectedly, and often people may not realize that they have a damaged tired until it stops working. If you don’t like dealing with unexpected flat tires or tire blowouts, it’s a good idea to check your tires every month to see how they’re doing.

When you check your tires, look for anything that looks unusual, such as cracks, gouges, or bulging. All of these are warning signs that your tires need to be replaced.

  • Tire Pressure

Checking your tire pressure is actually more of a preventative measure for tire health. If you are driving around with under-inflated tires, it can lead to greater wear on your tires. You should check your tire pressure every month or so, before big trips, and whenever the weather changes, since temperature can affect tire inflation.

Checking your tire pressure regularly can also alert you to a slow leak problem. If one tire consistently has low pressure, you may need to get it patched or get a new tire.

  • Age

Sometimes, tires just get old. Tires obviously wear out faster or slower depending on how much you drive and how well you take care of your tires. However, most tire manufacturers recommend replacing your tires every 6-10 years, regardless. Always check your specific tire manufacturer to see what they recommend.