Recently, I helped my mother purchase a new set of tires for her small SUV, a 2020 Mercedes GLB250. That might seem like a pretty benign declaration, but the shocking part is that it had traveled a mere 6,500 miles since new. So what happened? The vehicle is parked outside continuously and its sidewalls were badly cracked. Even though the tread depth was a healthy 7/32 of an inch, it was time for some new shoes.
Visible cracks on the outside of a tire can mean cracks on the inside, too. Think if you’ve ever tried to use an old, dried-out rubber band, only to have it break when stretched. If the steel belts inside a tire separate from the tread, it can lead to a loss of control or even a blowout. Some less catastrophic repercussions of old tires include air leaks, hydroplaning, and increased stopping distance during aggressive braking.
Even tires stored out of the weather have a limited lifespan before the rubber deteriorates to the point where it’s no longer safe to use. Several automakers, including Ford and Nissan, advise car owners to replace their tires after six years no matter how much tread remains. Meanwhile, certain tire manufacturers are more generous in their recommendations about when to replace tires. For example, Continental and Michelin advise motorists to replace tires after 10 years have elapsed, with the caveat that visual inspections for cracks be carried out every year after the tires hit their fifth birthday.
Check your DOT date code
Fortunately, it’s easy to tell exactly when your tire was manufactured if you know where to look. There’s no need to understand everything that’s written on your tires, but you’ll want to look for a small elongated oval containing four numbers. Those numbers represent the week and year during which a tire was manufactured. For example, if the number inside the oval reads “2719,” that translates to the 27th week of the year 2019. In other words, July 2019.
Do be aware when searching for a tire’s four-digit DOT code that it might be facing the inside of the vehicle. That could mean poking around underneath your car with a flashlight to find the born-on date, or possibly removing the wheel to view it. And it’s not uncommon for the DOT date code to vary slightly among a vehicle’s four tires — even if purchased at the same time — due to manufacturing and shipping variances. However, they should be relatively the same age. Think months apart, not years.
Finally, savvy consumers will check the DOT code on brand-new tires before leaving the tire store or mechanic. Even new tires that have never been mounted may have been sitting in inventory for a long period of time before being sold. That means a decreased lifespan for their new owner, which could score you a discount on the purchase price or perhaps render the tires unsuitable.
Don’t forget about the spare
Besides just sheer age, there are a few other factors that will shorten the lifespan of a tire, even if it still has plenty of tread remaining. In my mother’s case, we’ve already mentioned sunlight as a possible culprit, but hot climates and salty coastal air can also accelerate rubber deterioration. Ditto for tires that frequently come into contact with curbs. Proper inflation is also a contributing factor, with underinflated tires aging more quickly than those that are properly maintained.
The average driver in the United States racks up over 14,000 miles a year on their automobile. For most, tires are likely to wear out their tread well before a 10-year age limit is reached. Obviously, owners of collector cars or weekend drivers will accumulate fewer miles, as might city-dwelling car owners or retired folks.
Finally, don’t forget to check the age and appearance of your vehicle’s spare tire (unless, of course, you don’t have a spare, in which case, here’s what you should carry). It’s not hard to imagine going through one or more sets of primary tires without ever plucking the spare from its hiding place, so make sure it’s shipshape in case you ever do need to use it.
