Tire dry rot
Tire dry rot refers to the cracking and splitting that can occur in the sidewalls or treads of rubber tires as the rubber ages and becomes brittle. It’s also known as sidewall cracking.
Ozone and ultraviolet (UV) light are the primary environmental causes of tire dry rot. Tire manufacturers blend chemical ingredients into the tire during the manufacturing process in an effort to combat dry rot caused by ozone and UV exposure. Carbon black is added to the rubber to protect the tires from UV light. Waxes are added to the rubber during tire manufacturing to protect the tire against damage from ozone.
Why vintage cars are particularly at risk for tire dry rot
Vintage cars are particularly at risk for tire dry rot because they are typically driven infrequently, and may be stored for months at a time. Similarly, RV tires and boat trailer tires may dry rot long before the tread is worn.
The two primary causes of environment degradation of tires are UV and ozone and both may impact vintage cars that are parked for extended periods of time. UV rays damage any rubber that is left exposed to direct sunlight. Ozone will degrade any rubber that is exposed to the air.
- Keep tires out of direct sunlight whenever possible. Garaging your vintage car, or at least covering the tires when it is stored outdoors, can help prevent UV damage.
- Move the vehicle periodically when it is in storage if possible. Flexing the tires during movement helps the protective waxes to work their way to the surface where they can protect against ozone.
- Use only tire protectants that do not contain petrochemicals or harmful silicone oils. These ingredients may strip protective waxes from the tire and speed degradation. A product like 303® Aerospace Protectant™ is an excellent choice to protect tires on vintage cars because it does not contain dangerous petrochemicals or harmful silicone oils, and does not remove the protective waxes that are blended into the tires. 303® Aerospace Protectant™ is actually absorbed into the rubber where it delivers unique, powerful UV stabilizers to further prevent degradation. When using 303® Aerospace Protectant™ on wheels and tires, care must be taken to minimize spray onto the brake discs. Excessive over-spray will lengthen stopping distances until the formula wears off.
Protecting the tires on your vintage cars from UV and ozone damage is a process. To learn even more about protecting the tires see our tip sheet on Storing Your Hot Rod, Muscle Car or Collector Car.
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