Why are Tires Black? Left alone, tires dry out, discolor and eventually crack and split. “Dry rot” is a multi-million dollar problem for RVers, trailer boaters and owners of classic cars that are parked for extended periods.
The major factor degrading tires and other synthetic and rubber products is ozone, an odorless gas which is part of the air we breath. When combined with ultraviolet light (the invisible part of sunlight) a reaction occurs that attacks the tire polymer.
To protect against ozone and UV damage, a stabilizer molecule called a “competitive absorber” is blended with the tire polymer. Competitive absorbers work by capturing and absorbing UV radiation and converting it to heat which is dissipated harmlessly. All tire manufacturers use the same competitive absorber, carbon black. This is why all tires are black...why tires are not available in designer colors.
These absorbers are sacrificial; they expend themselves in performing their function of changing UV to heat. As carbon black loses it’s ability to perform, it turns gray. This is one reason why black tires discolor as they age.
To protect from further ozone damage, tire manufacturers add a wax compound to their formulas. Tires flex when they are in motion, causing the wax molecules to migrate to the surface. This forms a protective barrier between the air (ozone and oxygen) and the tire polymer. In the tire trade this is called “blooming”.
When tires are parked for extended periods, blooming does not occur and ozone starts attacking the polymer. With UV light and ozone working in concert, the degradation is accelerated, resulting in drying, discoloration and cracking.
The best product we know of to retard ozone and UV damage is
303 Aerospace Protectant. A quick spray of 303 Protectant leaves tires looking great and protects them with the equivalent of an SPF 40 sunscreen.
