If you're familiar with the penny test, then you're probably familiar with the idea that you should replace your tires once the tread is no longer at least 1/16 of an inch deep. This depth provides a good rule of thumb, but an often overlooked aspect of the penny test is that you should check your tires at multiple locations. Many drivers check once, find the tread acceptable at a single spot, and assume that their tires are perfectly fine for at least several thousand miles more. While this is a reasonable assumption under ideal circumstances, you will soon see that it fails in the real world.
Tire Wear Explained
As your car travels across the road, a limited section of rubber known as a contact patch makes the actual connection. This thin portion of your tire's rubber is the only part of your vehicle in contact with the ground, so it has an incredibly vital job to play in your vehicle's performance, handling, and safety. When everything is in perfect working order, your tires will smoothly rotate, and the geometry of the contact patch will remain essentially the same. As the tire rotates, the tread will wear evenly around its surface.
Of course, the real world is rarely so ideal. Your car's suspension and steering components are responsible for keeping your tires straight and firmly planted, ensuring that the geometry of the contact patch remains even and correct. Worn parts, imbalanced tires, or improper alignment can cause your tires to bounce excessively or make uneven contact with the road. As this happens, the tread on your tires will wear unevenly. The result of this process is reduced handling and a tire that may be wearing much more quickly on its inner and outer edge.
Reducing The Effects Of Uneven Wear
No car is perfect. Suspension components begin to wear as soon as a vehicle leaves the factory, and tiny imperfections can result in minor variations in tire wear. These variations can build up over time, causing your tires to wear more quickly or degrade in performance. Regular tire rotations are necessary for precisely this reason, since changing the position of your tires will help to spread wear evenly and prevent one tire from wearing at a much faster rate.
Should You Replace Unevenly Worn Tires?
Now that you have a better understanding of how tires can wear, it might be clear why purchasing new tires is sometimes necessary even when your existing tires still have tread left. When inspecting your tires, check the tread depth at multiple locations along the center as well as the inner and outer edges. If any portion of the tire has tread that falls below the minimum acceptable depth, then it's time to buy new tires. It's also a good idea to determine the underlying cause of the problem so that your fresh rubber doesn't suffer the same fate.