It’s that time of year when you switch from winter to summer tires. Or perhaps you bring that special car out of storage for its annual run in the sun.
In either case, this is a perfect time to take a close look at the tires.
Although they might have only run a few thousand miles and show plenty of tread, they most certainly will not provide as much grip as the last time you drove on them.
A tire’s biggest enemy is heat. Other than damage caused by potholes or misalignment, tire failure is commonly due to excess heat created by under-inflation or overloading.
But few motorists realize that tires are perishable commodities that become less effective with age.
Whether mounted on a special vehicle trailered to shows, stored for extended periods and driven only occasionally or used for very low mileage situations, such as that weekly drive to the post office from the retirement community, 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.
A few years ago, the British Rubber Manufacturers Association issued a statement “strongly recommending” that all tires should be replaced 10 years from the date of manufacture. It said 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.”
The problem is not one of wear, but of age. A variety of factors, including exposure to sunlight, climate, frequency of use, and storage may actually accelerate the aging process.
Under ideal conditions, which rarely exist, tires can be expected to retain their designed effectiveness for up to 10 years from the date they rolled out of the mold. There is no way to detect age-related problems visually, even for an experienced tire professional.
There are no known non-destructive tests to assess long-term serviceability. But it is generally acknowledged by industry experts that tires will “age out” before they wear out, in circumstances where they are used infrequently.
Tires are a combination of rubber, sulfur and a variety of compounds cured through heating. The cross-linking of sulfur with various polymers when exposed to heat helps make rubber both elastic and durable.
But despite considerable research, effort and the use of age inhibitors, these sulfur molecules are reactivated every time a tire is exposed to heat. Another issue is that the oil contained in the rubber used to make tires, tends to migrate through the casing and tread and evaporate. As the compound loses oil, it becomes harder.
High-performance tires, because of their chemical composition and construction, not only wear more quickly, but have a shorter shelf life than general use tires.
It is not uncommon for a “new” tire to be one to two years old before it reaches the end consumer due to manufacturing location, shipping, stocking, seasonal and other considerations.
Inactivity is a major contributor to tire aging. Tires will age to some degree regardless of what we do. Here are some steps to help slow the process while tires are in storage.
Don’t store a vehicle with weight on the tires for lengthy periods.
Avoid the use of tire dressings. Manufacturers say the chemical composition of tires includes provisions to resist the effects of weather checking and ozone cracking.
Store tires in a cool, dry, dark location away from the harm caused by the sun’s rays and heat
Store tires in air-tight plastic bags available from tire dealers or you can use garbage bags. Use a vacuum cleaner to draw air from the bag and seal it with tape.
Avoid storing tires where they will be exposed to the ozone caused by electric motors i.e. near furnaces, sump pumps and in workshops.
TELLING A TIRE’S AGE
The U.S. Department of Transportation and Transport Canada require a Tire Identification Code or Serial Number on the sidewall comprised of 11 or 12 numbers and letters that identify the name of the manufacturer, the location of the production facility, tire size and the date the tire was built.
The last three or four digits indicate the date of manufacture. From Sept.1, 2000, all tires must use four digits to indicate the date i.e. XXXXXXXX3516 which would tell you the tire was produced during the 35th week of 2016.