Tires age whether they are stored or installed on a vehicle; stored tires may age at slower rates, but they still do. Worn out tires are dangerous – they can burst (due to thread separation) without any warning. To understand just how this is possible, you need to know what happens when tires age, and the factors that accelerate the damage.

The Damage 

The elasticity of rubber is integral to its longevity. The primary material of tires is rubber, which loses its elasticity as it ages. This happens because of the breakdown of the oils and chemicals that comprise the rubber. This is not good because it is the elasticity that helps tires to roll on the ground and take different shapes without getting damaged or cracking.

When the elasticity is lost, cracks begin to occur both on the surface and inside the rubber material. Eventually, the steel wires within the tire also separate; imagine just how dangerous it would be if this happened at high speeds. Not that anti-aging compounds prolong tires' lives, but they don't prevent aging.

The Accelerants

As hinted in the introduction, there are factors that increase the rate of aging of tires, and they include:

• Conditions of use – use your tire according to your manufacturer's recommendation if you don't want it to age fast. Underinflated tires bulge due to the weight of the car, and this deformity wears it faster. Inflate your tires to the correct pressure and use them on the right vehicle. Tires that ride over rough roads, hit too many curbs, and have been repaired too many times also age faster.
• Heat – high temperature increases the rate of reactions of most chemical processes. The breakdown of rubber, which is a chemical process, also accelerates if it is exposed to heat. Therefore, storing your spare tire in the sun or the hot confines of the trunk ages it faster even if you rarely use it.
• Chemicals – exposing your tires to different chemicals also speeds up the aging process. For example, oil, tar, petrol and paraffin all soften rubber. When the rubber softens, the chemicals seep deeper into the tire and cause even more damage.

There is no universal date by which you should replace your tires; it's best to follow the respective manufacturer's directions. Take care of your tires well, for example, by not exposing them to high temperatures. If you have been mistreating your tires, then it's wise to replace them just before they reach the manufacturer's indicated date. Contact a local auto repair shop, such as Duncan Tire & Auto, for further assistance.