Excerpt from an article in Modern Tire Dealer,December 2002
Q
o Tires Have a Shelf Life?
A: Tires do not have expiration dates, based on my talks with tire manufacturers. The reason is simple: There is no way for tiremakers to control how their tires are stored or used.
"Tires are still manufactures with a percentage of natural rubber, which does deteriorate with age," says a Michelin spokesperson." Because of this, most tire manufacturers have a time limit on the warranty, which is typically six years."
Tire compounding is such that as long as you store your tires properly, they can last a long time without significant degradation. A tire starts to age the moment it leaves the curing press," a tire engineer friend told me. "All rubber components on the car, from the power transmission belts to the engine mounts to the tires, age. But in certain environments, they age a lot faster." Elements such as oxygen, ozone, and heat greatly affect tires, he adds.
Exposure to simple oxidation can't be avoided, at least on the outside of the tire. Over time, it will cause cracks in the compounding. Although some of the dozen or so ingredients in a tire help it resist oxidation, it can't be completely prevented.
Ozone is a form of oxygen that degrades organic matter, like rubber. For example, if a tire is in a factory where there are ozone-producing devices such as welders or electric motors, it will have its life span shortened dramatically.
Some of the waxes, oils, and protective chemicals designed to help control the effect of o on a tire work while the tire is stored at room temperature: others work while the tire is in motion.
The Rubber Manufacturers Association does not have a standard in respect to tire age. It has issued a service bulletin on proper tire storage, which it says will limit exposure to potential damage.
Store them in a clean,cool,dry, dark, and well-ventilated area (but with a minimum of circulating air). Keep them away from direct sunlight.
Stack them so that the tire on the bottom retains its shape.
Place an opaque, waterproof covering over the tires if they are outdoors," but avoid creating a steambath."
Store the tires whitewall to whitewall, to avoid staining
Store the vehicle on blocks to remove all weight from the tires
If the vehicle cannot be blocked up from the storage surface, completely unload it so minimum weight will rest on the tires. Keep tires, including the spare tire, inflated to recommended operating pressure. The surface should be firm, reasonably level, well drained, and clean.
Move the vehicle at least every three months to prevent ozone cracking in the bulge area and also to prevent a "flat spot" from developing( due to strain from deflecting). If tires do develop a temporary "flat spot," it will usually disappear in a short period of time(for example, the first 25 miles of service)
