Tires, Aging

Tires age as a result of physical and chemical processes whereby the function can be impaired. Tires which are stored for longer periods of time become harder and brittle faster than tires which are constantly in use on a vehicle. Older tires may develop hairline cracks from aging. When tires are in constant use, the kneading activates softeners in the rubber, preventing hardening and the development of cracks.

Therefore, one should note not just the tread depth but also the age of spare tires, stored tires and tires which are not permanently in use. Tire age can be determined from the DOT code which contains, among other things, the tire's production date.

Example of a DOT number:

In this example, the production date is the 50th week in 2002. Through 12/31/1999, the DOT number was a three-digit number.

Recommendation: 

• It is recommended using tires more than 6 years old only in emergencies and only with a cautious driving style.
• When new tires are fitted, the spare tire may also be used if it is in flawless condition and is not more than six years old. The age of the tire has a great influence on the high-speed capability of the tire. The combination of a spare tire which is several years old with new tires is possible, but it can influence the car's handling.
• Tires are constantly being further developed, this can lead, for example, to slight changes in the rubber compound, even if the tires are of the same make, size and tread.
• For driving safety reasons, tires of the same make and with the same tread should be mounted on one axle.
• Vehicles with AWD always must be equipped with four wheels that have tires of the same size, construction, tread pattern and make. Excepted are vehicles that were shipped by Audi AG with different sized tires on the front and rear axle.