If the tires on your vehicle have logged some miles, you might want to take a closer look. Over time, tread wear patterns will indicate whether your tires are properly balanced, aligned and inflated.
When a car is in good mechanical condition and tires are properly inflated, tread wear appears even. Looking down the face of the tire from inside to outside, there should be no noticeable difference in wear. Running a palm down the face of the tire should reveal a smooth, uniform surface without undulations. If the mechanical condition of the front-end is not so tiptop, it will show in the tread wear.
For example, when tires are not balanced, the vehicle will vibrate at certain speeds and the steering wheel might shake. Tread wear in this case becomes "cupped" down the face of the tire. Tread depth undulates unevenly, felt easily by running a palm down the tire.
Cupped tread wear comes from the tires "bouncing" at certain speeds due to the unbalanced weight of the tire. A rough parallel might be to consider how a washing machine in the spin cycle can begin to "bang off balance" when the weight of the clothes is unevenly distributed. To balance the tires, weights are placed on the rim to keep the tires rotating smoothly at any speed.
Alignment is another front-end adjustment. When tires are not aligned, the driver feels a right or left pull on the steering wheel and the car will tend to veer in the direction of the pull. Due to the constant corrective pull, mileage is slightly reduced and the front tires wear unevenly. The inside tread might wear faster that the outside, or vise-versa, depending on how the alignment is off.
Once tread wear becomes uneven, correcting the alignment will not make the steering feel completely normal, as uneven tread creates its own friction against pavement. In most cases, a mechanic will rotate these tires to the back. As long as there is plenty of tread left, they will eventually wear even again. However, if tread wear is excessive at the edges, tire replacement is necessary. This can be a costly lesson, as the tires may only have a fraction of the miles they are designed to reach under normal circumstances, and plenty of tread elsewhere on the face.
Tread wear can also occur when tires are routinely driven over-inflated or under-inflated. Driving with under-inflated tires can ruin sidewalls prematurely, creating cracks and weaknesses in tire walls. Conversely, driving with over-inflated tires will eventually cause accelerated tread wear down the center line of the tire face, as compared to the inner and outer edges.
If purchasing a used car, check tread wear carefully. If the vehicle has new tires, they could be hiding front-end problems. You might ask for receipts to be sure the newly installed tires have been balanced and aligned, or be prepared to have the work done yourself.
With our current dependence on vehicles, people log many miles but don't always find time for routine maintenance. Checking tread wear is one way to quickly see if the tires are balanced, aligned and properly inflated. Regularly rotating tires from front to back also helps keep tires wearing evenly, as front tires normally wear faster than rear tires.
Aside from car maintenance, tread wear patterns are also used in forensic science. Casts of tread impressions left at crime scenes can not only reveal the type of tire, but unique characteristics in tread wear patterns which can provide strong circumstantial evidence to link a specific vehicle to a crime.