Exposure to heat, light, and the elements can reduce the life of your tires. If you have to store tires, here are some hints to help prolong their lives.
All those thousands of miles you driven have accumulated brake dust, dirt and perhaps road grime. Before you store tires, you should first clean them thoroughly. Don't let these compounds sit on the tires for a long period of time, they can damage the tires. Clean the tires with soap, water and a soft brush. Use a towel to wipe the tires clean, and let any remaining moisture evaporate. Don't apply any additional shine products to the tires.
Once your tires have dried completely then its time to place each tire in a dark colored bag to keep the light from hitting them. The bags preferably should be airtight, this will help keep the oil within the tire compounds from evaporating. Avoid seasonal tire totes, while these totes are convenient and make carrying easier, they are not airtight and they do not necessarily protect the tires from the atmosphere.
The sun's ultraviolet rays can cause rubber to deteriorate more quickly than normal.
When it comes time to store your tires, make sure you store them in a cool, dry location such as a basement, climate-controlled garage, or workshop. Avoid storing the tires outdoors, in a standard garage, or in an attic that can become very hot or cold and/or be exposed to extremely wet or humid seasonal conditions. Ozone also damages tires. Therefore, do not store the tires near machinery that can generate ozone such as motors, pumps, or furnaces.