Do tires expire?

I was once in a seminar organized by a reputable tire company. They were introducing a new line of performance tires. In the Q&A, which almost always happens before a sumptuous buffet, I asked the shelf life of the tire and its expiration date. 

I didn’t realize this question would stretch the event beyond lunch time. Enthusiasts, Media and Engineers were debating over the shelf lifeof tires for over an hour.The seminar ended with this simple fact - Expired tires are dangerous as it can crack, deform or explode, regardless of tread depth.

But the expiration in terms of years was never resolved. In my experience, some do degrade faster than others and a lot of factors may play a part in the degradation process, but all of them expire on the average of around 8 years.

The British Tire Manufacturer’s Association highly suggest to change tires if it’s beyond 10 years old. The US NHTSA (National Highway Traffic Safety Administration) says 6 years. I couldn’t find any research done for the Tropical SEA Countries.

But it’s good to know that almost all commoditiesin the Philippines today have expiry date label. This includes our car’s tires. Every tire has a date of birth – when it was manufactured. It’s always engraved/printed on the side of the sidewalls of the tires.

But surprisingly, most end consumers and even tire retailers are unaware of tire shelf life and expiry dates. You might think you’re buying a new set of tires when in reality, those tires could have been sitting on the retailer’s storage for years.

Vehicle owners have always relied on the “coin test” to determine if a tire needed to be replaced. Put a “piso” in the treads. If the treads reach beyond the outer letterings of the coin(Republika ng Pilipinas), it’s good. Below that, the tires are too worn out. The “piso test” only gauges tread depth and it’s not really accurate on A/T(All Terrain) or SUV Tires.It also does not include the age of the tire, which is a fatal mistake. It’s a simple fact. Expired tires are dangerous, regardless of tread depth.

So how can we protect ourselves? When buying tires, look for the tire’s manufactured date. It’s typically a 10- or 11-character DOT (Department of Transportation) code, embossed or stamp on the sidewall of the tire. Check the last four digits. The last two refer to the year the tire was manufactured, the first two (of the four) represent the week number. For example, 0419 tells you the tire was produced in the 4th week of 2019. This is especially important with Sports Utility Vehicles and Trucks as they are heavy vehicles or carry heavy loads.

So, what happens when tires age? Over time, the rubber compound starts to break down. Symptoms are small cracks on the sidewalls and inside the tread of the tires. You will also see bumps on the sidewall which are particularly dangerous as this means that the steel reinforcements inside the rubber have already snapped. 

Over time, these symptoms will cause the tire to explode. If the tires are under or over-inflated, out of balance or misaligned, the entire process is accelerated.

New tires that are kept well by retailers last longer than those expose to the elements of the weather. But like everything on this planet, tiresdo succumb to the ravages of age, even if it has not touched the road yet. It’s vital to know the date of manufacture.

So now you know, you can check those old set of spares that have been sitting in the back of the car. If you want to continue using them, here’s a thought. You reach out for the box of milk that has been sitting in the ref for a month. It already smells bad; would you risk it?