Tires are a mystery for many drivers. You know they have to be replaced regularly, but why do some tires wear faster than others? What happens to your car's handling as your tread wears down? Are worn tires really dangerous? Understanding the answers to these questions can help you to ensure that your tires last longer and that you make better decisions when it's time to service or replace your tires.
Some Basic Terminology: Tread and Grooves
When you look at the average street tire, the thing that you usually notice first is the tread pattern. Many people refer to this pattern of grooves and raised rubber as the tire's tread, but this is actually a misunderstanding. A tire's tread refers only to the portion of the rubber that actually makes contact with the road surface. For street tires, the tread is cut with a pattern (referred to as a tread pattern) of grooves. The purpose of these grooves is to provide an escape path for water that's trapped between the tire and the road.
In dry conditions, the tread pattern actually limits the tire's traction. Racing tires (commonly known as racing slicks) which are only used on dry tracks have no tread pattern at all. Instead, the contact area of the tire is a solid patch of tread. This provides the best possible dry traction by maximizing the amount of the tire's surface that makes contact with the road, but it is dangerously limiting in wet conditions. Street tires attempt to strike a balance by using tread patterns which maximize the size of the contact patch while still providing a way for water to escape.
Friction: Friend and Foe
Traction is what allows your car to function properly. Without traction, you wouldn't be able to accelerate, brake, or turn, but what is traction? Put simply, it's the friction between your vehicle's tires and the road surface that you're traveling on. Friction is necessary for your car to be safe or drivable at all, but friction creates heat which in turns creates wear on your tires. As they travel along the road surface, the friction they create wears down the tread. Over time, the tread will be worn away entirely.
What Happens as Tread Wears?
The tread on your tire is what provides that all-important friction that you need to keep your vehicle planted. As the tread wears down, the grip provided by the tires is decreased. Unfortunately, this usually means that the tire's ability to perform at its limits is lessened. In other words, the tire may continue to feel fine under normal driving conditions, but may suddenly lose grip if pushed hard. Worn tires are also more susceptible to failing entirely, and old tires are prone to blow-outs and tread separation.
With street tires, worn out tread has an additional effect as well. Remember, the purpose of the grooves is to provide safe handling in wet conditions. As the tread wears down, your tires become more like racing slicks: the difference between tread and groove vanishes and the tire becomes smoother. This can easily lead to hydroplaning and poor or even dangerous handling on wet surfaces.
Although they can be easy to ignore, worn tires are dangerous and should always be replaced as soon as possible. If your tires aren't yet worn out, regular tire rotations and proper air pressure can help to ensure that your tires wear evenly and provide safe traction for as long as possible. Seek out auto services for more help with tire replacement.