Safety

• Dry rot can affect tires that have substantial tread left. Cracking results in an unsafe tire that must be replaced, because its treads can separate. To increase tire life, manufacturers blend chemicals into tire polymers to slow damage from ozone and sunlight, according to AcuraVigorClub.com. Carbon black, which makes tires black, is a "competitive absorber" that absorbs ultraviolet light and converts it to heat. The cumulative effect of exposure to sunlight causes carbon black to turn gray.
  
  

Wax and Blooming

• Another substance that manufacturers add to tires is a wax that protects against damage by ozone. When tires flex during driving, they squeeze the wax out onto their surface, where it forms a protective coating against ozone. This process is referred to as blooming, according to 303Products.com. Tires on vehicles that are not driven for long periods of time are more prone to dry rot, because no blooming is occurring as a measure of protection.
  
  

Additional Facts

• Other substances that can hasten tire deterioration are silicone oils and chemicals such as tire dressings, as well as protectants that can dissolve the protective waxes, thereby accelerating damage to the polymers. Use of such substances can void a tire warranty.