You can actually read your tire's wear like a book if you know what to look for. Understanding and learning to recognize the different tire wear patterns can help you know when it is time to have your tires replaced. It can also provide a guide for determining any other issues your car may be experiencing.
1. Side Wear
Side wear occurs on the part of the tire that is in contact with the road, but it only affects the side treads of this surface and not the center tread. Only one side may be affected, or both sides may show more wear than the center of the tire tread. If one side of one or more tires is worn, the issue is likely with the car's alignment. Wear on both sides may indicate alignment issues or the tire rod could be bent or otherwise damaged.
Cupping literally looks like someone uses a spoon to scoop out the tire's tread. There are usually a series of cupped areas going around the entire circumference of the tire. Cupped tires lead to a bouncy ride, and they must be replaced for safety reasons. The cause must also be repaired. Cupping is usually a result of suspension issues, such as worn-out shocks or failure in a hydraulic suspension arm.
3. Center Wear
Center wear is much like side wear except it is only along the center of the tire tread. The culprit isn't a problem with your car, but with tire care. When tires are overinflated they do not sit flush to the road as designed. Instead, the center of the tire bulges out with the excess air, which leads to uneven weight distribution and thus uneven wear. If caught early and remedied, it will only marginally affect the tire lifespan. Major wear will require new tires.
4. Flat Wear
Similar to center wear, flat spots can develop on the center of the tread. The main difference is that the tread isn't just worn, it is completely flattened due to a combination of heat and friction. Hard braking is the cause of flat wear. The tires will need to be replaced as they will no longer have proper traction and they will be more prone to punctures.
5. Sidewall Wear
Any damage on the sides of the tire and not the contact surface is sidewall damage. Running into curbs is the most common culprit. Sidewalls can also develop bubbles from age or from frequent driving on rougher roads. Sidewall wear increases the chances of a blowout, so replacement is advised.
Contact a tire and alignment service if you need more help with your worn tires.