If you are about to take the winter tires and/or wheels out of storage and put them on your vehicle for the coming months, take a minute to check them out.
Take a close look.
They might have only run a few thousand kilometres and have plenty of tread, but they most certainly will not provide as much grip as the last time you drove on them.
If used and stored properly in a dark, cool location, tires will retain their original design efficacy for up to five years, but all tires loose some of their effectiveness with each use.
Tires age because of a chemical process called oxidation. The oxygen particles in air cause the flexible components of a tire to harden and become brittle.
In 1973, the average tread life of a passenger or light truck tire was approximately 40,000 kilometres.
By 2003 that had risen to 75,000 km. Tread life has more than quadrupled over the last 45 years. Some manufacturers promise 100,000 miles of tread life.
But, as tread life becomes less of a factor, age through oxidation becomes a serious concern.
Whether mounted on a special vehicle trailered to shows, stored for extended periods and driven only occasionally or used for very low mileage situations, tires will age out before they wear out under low-mileage conditions.
So much so, that there is growing concern about the safety of very old tires. Safety experts feel expired tires are a hidden hazard.
The U.S. Department of Transportation says more than 11,000 tire-related crashes happen in that country each year.
The NHTSA (National Highway Traffic Safety Administration) says tires expire in six years.
The British Rubber Manufacturers Association “strongly recommends” that all tires should be replaced 10 years from the date of manufacture and that unused tires should not be put into service if they are more than six years old.
Manufacturers of high-performance European cars clearly state in the owner’s manual that, “under no circumstances should tires older than six years be used.” Ford, GM, Toyota, Dodge, BMW and other manufacturers advise that tires expire in six years from the date of manufacture.
Most consumers don’t know that tires expire in six years, nor do they know how to tell the age of the tires on their vehicle.
The answer lies in reading the code stamped on the sidewall of each tire.
The U.S. Department of Transportation (DOT) and Transport Canada require a Tire Identification Code or Serial Number to be “clearly branded or etched” on the side of each tire. In most cases there will be 11 digits. If there are only 10, the tire was manufactured before 2000.
How to read your tires? Here’s an example from a tire produced in the 48th week of 2015:
- DOT EL 9N DEA4815
- DOT — Department of Transportation
- EL — Manufacturer and plant code
- 9N — Tire-size code
- DEA — Manufacturer identity number
- 4815 — Date of manufacture
Those last four digits are the critical ones. Numbers eight and nine (48) indicate the week of manufacture, and the last two digits (15) the year — 2015.
It is not uncommon for a “new” tire to be one or more years old before it is installed on a vehicle or reaches the end consumer due to manufacturing location, shipping, stocking, seasonal and other considerations.
For the same reasons, it is not uncommon for each tire on a new vehicle to vary in age.
Now that you know how old your tires are, how should they be stored? In airtight plastic bags, in a cool, dry, dark location away from the ozone caused by electric motors (i.e. near furnaces, sump pumps and in workshops).
If you really want to ensure maximum protection, use a vacuum to suck air from the bag and seal it with tape.