Originally Posted by
cyccommute
UV exposure probably doesn't have a large effect on aging of rubber. It does some damage but not all that much. Think car tires that are exposed to sunlight all the time. What dsbrantjr is talking about is the production of ozone via the exposure of other chemicals - unburned hydrocarbons and oxides of nitrogen -to UV light.
The formulations used for the butyl rubber will also make for a highly variable rate of reaction with ozone.
I knew a guy that purchased a 1958 car with the original tires that sat outside for about 40 years or more and the tires still held air, they were cracked very badly, but they held air so he could roll it onto a trailer.