Tires Can Wear Out Even If They Haven’t Gone Very Far
If you must buy used tires to outfit your vehicle, there are some important points to consider before you take the plunge.
A tire begins to diminish the moment it leaves the assembly line. Its first hundred miles is the best it will offer and it’s downhill from there. Between six and 10 years, its rubber and internal components will begin to get the tire equivalent of hardening of the arteries, often called dry rot. Tires are like humans that way: They can degrade and weaken even if they haven’t gone very far or done much. Prime example: your grandmother’s 9-year-old car may only have 10,000 miles on the odometer, but it needs new tires.
Some car makers, including Mercedes-Benz, recommend removing a tire that’s more than 6 years old, even if plenty of tread remains: Mercedes knows some of its vehicles will reach 155 mph on the curvy German autobahn and the blazing-hot highways of Saudi Arabia. (Though not recommended, they could also top 100 on Tennessee’s Interstate 40, which the late auto journalist L.J.K. Setright called “the fastest autobahn in the world.”)
The tire industry argues that it’s nearly impossible to accurately determine age-related damage. That’s because a tire that waits for its first owner in a carefully climate-controlled tire-company storage warehouse is in something like suspended animation. However, one left in the sun on display may be almost worn out inside before it’s mounted on a vehicle. And the ones I put in the cool crawl space under my house in garbage bags are somewhere in between. Still, some tire companies recommend tires that have been in service for 10 years be replaced.
Almost every driver can find out a tire’s age just by decoding numbers on the tire. Your tire’s “born-on date” is on its sidewall, part of the government-required Tire Identification Number (TIN), according to SafeCar.gov. The TIN is an alphanumeric code that begins with “DOT” (the abbreviation for the U.S. Department of Transportation). The last four digits indicate the week and year in which the tire was made. A TIN ending in 0112 means the tire was made in the first week of 2012. (If the DOT code ends with a letter or contains less than 10 digits, check the opposite sidewall. If you can’t find such a number or its been ground off, assume the tire is far too old for safe use.)
While there is no way to track the history of a used tire, it’s safe to assume the used tire likely was driven underinflated: A recent study by the National Highway Traffic Safety Administration (NHTSA) found that even new cars with Tire Pressure Monitoring Systems (TPMS) often have at least one severely underinflated tire. Also, a used tire could have suffered significant damage from a pothole, been repaired improperly, or permanently damaged when being dismounted. Make sure to have the used tire properly inspected by a tire professional before purchase and installation.
If you’ve just acquired a used car and face otherwise untraceable issues with tire wear, handling, excessive noise or the like, check to make sure all four tires were produced at the same plant at about the same time. It’s ideal if the TINs are identical on all four tires and, if applicable, the spare.
Tire companies, like the manufacturers of just about every other product, often make changes during production runs and sometimes produce the same product in multiple plants. A tire made a couple of years after — or in a different plant than — its otherwise visually identical sibling may have subtle but important differences. The plant code is immediately after DOT on the TIN. You can find where your tire was built at the NHTSA’s Product Information Catalog and Vehicle Listing.
Remember to check your spare tire. (You may find you don’t have one!) It’s possible to have a spare that’s never touched the ground but is so old that it should be thrown away. And finally, to ensure your tires are properly inflated, SafeCar.gov suggests you check the tire pressure of all your tires (even the spare) monthly.