In 2008, the Georgia owner of a Ford Explorer replaced his flat tire with a used tire. This type of replacement is common practice when the other three tires on the vehicle have notable wear. A brand new tire would not be a good match for the rest of the set. So, rather than buy four new tires, the owner put his trust in a used tire with similar wear to the rest of the set. Two weeks later, the tread on the replacement tire suddenly separated from the rest of the tire. The driver lost control of the vehicle and hit a motorcycle, killing the driver. An investigation into the cause of the accident revealed that the used tire was ten years old, a full four years beyond the recommended life of a car tire.
When you think about the safety features of your car, what comes to mind? You probably thought of the seatbelts, airbags, headlights, and anti-lock brakes. However, your tires are one of the most significant safety features on your vehicle because they are the only point of contact between your car and the road. If your tires do not grip the road, your brakes can’t stop the vehicle, and you can’t swerve to avoid a pedestrian that darts out in front of you. Your tires affect the reliability of the other safety features that keep you safe.
The most noticeable location to see tire wear is on the tread. New car tires typically have about 10/32nds of tread, meaning that the height difference between the rubber surface that contacts the road and the lowest part of the channels in the tread is 10/32nds of an inch.
As you drive your car, friction and heat from contact with the road wear down this rubber surface. When it gets down to 2/32nds, it is time to replace your tires. While this is the United States Department of Transportation’s recommendation, it is also the law in many states.
The amount of tread left on your tires is easy to measure and can tell you definitively when your tires need replacing. However, it is only half of the story. If you rely solely on this measurement to determine if your tires are safe to drive on, you may miss some obvious and dangerous problems.
Waste rubber tires are a familiar problem. They don’t biodegrade and can sit in dumps or landfills for years. From this little bit of information, you may conclude that rubber is nearly indestructible. However, this misconception leads to some of the most significant tire safety problems.
The components of car tires do break down with exposure to ultraviolet light and ozone in the atmosphere. It does not decompose, but it changes from a soft, pliable product to something dry and brittle. When the tire loses its elasticity, it begins to develop cracks. You can see these cracks develop in the sidewalls of your tires. What you may not see is that the rubber could be cracking on the inside of the tire as well. Even if your tires still have plenty of tread left on the wear surface, you should replace them if they are hard and brittle.
Cracks are just the first sign of trouble, but even at this phase, you may notice increased braking distances and reduced responsiveness to steering changes. As the rubber ages, it also becomes more porous, allowing air to leak out more quickly. You may find yourself topping up the air in your tires frequently. If you ignore these problems, you accept an increased risk of your tires delaminating and coming apart while you are driving. Delamination is a severe problem that often leads drivers to lose control of their vehicles. It is best to replace any tires at the first sign of trouble to avoid serious injury.
While it would be helpful to have accurate expiration dates for rubber tires, determining exactly when they become unsafe is tricky. According to the Rubber Manufacturers Association (RMA), many factors affect the aging rate of tire rubber. Driving conditions, temperature, and storage conditions all play a part. Knowing when the tire was made can be more helpful in determining its expected lifespan.
In 2000, the United States Department of Transportation started requiring tire manufacturers to mark their tires with a code. This DOT code allows drivers and tire shops alike to find out more about every tire on the shelf or on the road. The four-digit code tells what year and what week of the year the tire was manufactured. For example, a tire with the code 0420 was made the fourth week of 2020.
Most carmakers agree that consumers should replace their tires six years after the date of manufacture. For many drivers, this recommendation is easy to follow. If you drive an average of 12-15,000 miles per year, you are likely to wear out the tread on your tires before the rubber gets old.
Age becomes a more significant problem when you drive less. The tires on seasonal cars such as convertibles or classic vehicles that may sit in the garage for extended periods may need replacing long before the tread is gone. Likewise, RV tires and spare tires may not get much use in their short six-year life. Regardless, it is still important to replace them regularly to prevent accidents.
Tread depth and wear are essential factors to consider when evaluating the safety of your tires. However, it is arguably just as vital to inspect your tires regularly for signs of aging. You can check your tires’ DOT code yourself, or you can have a trusted mechanic at your local Utah tire shop help you keep an eye on them. The tires on your vehicle do more to keep you safe than you may realize.