RVs, boat trailers and classic cars all have one thing in common. They remain parked for long periods of time, so their tires are not "exercised" or regularly used, leaving their tires susceptible to the onset of dry rot. Once dry rot sets in, the tires deteriorate rapidly and need to be replaced.
Several factors set tires up for dry rot to set in. Ozone and ultraviolet light (UV) are the chief environmental degradants that set up tires for dry rot. The tires have a wax added to them to help them flex while driving. However, the lack of exercise in vehicles parked for extended periods causes the rubber to become unflexible, especially the rubber sitting on the pavement. Certain petrochemical-based tire cleaners can strip the protective waxes and attack the rubber.
Once the tires have been compromised, Serpula lacrymans, the fungus responsible for dry rot in wood, sets in and eats away at the rubber. When dry rot sets in it can cause the rubber to become unstable and lose strength. This could lead to blown tires and accidents.
Tire makers add chemicals to the rubber during the manufacturing process to slow damage that ozone and ultraviolet light cause to tires. The chemicals, called "competitive absorbers," convert UV wave energy to heat that dissipates easily, preventing UV absorption by the tire polymers. A few tire cleaners are available that do not strip the tires of their wax protectants.
To prevent dry rot in tires, perform routine maintenance and other practical measures. Routinely check tires for proper inflation. Drive the vehicle regularly to keep the tires moving and flex their "muscles." Shine tires with a non-harmful product or don't shine them at all. Don't park cars near electrical appliances which emit ozone, as the additional ozone can speed up the dry rot process.
Storing tires in cool, dry, areas with no sun cuts down the exposure to ozone and weathering. Storing them away from asphalt and other heat absorbing surfaces as well as highly reflective surfaces will protect them from ultraviolet light. Stacking them flat helps tires maintain their shape. Tires stored still on the rims will maintain shape better if filled to 10 PSI during cold months and 15 PSI during warm months.