I believe that Ozone and UVB/UVB are the main things that will damage rubber products (including campagnolo gum-rubber hoods). For UVA and UVB, something like garden-variety drugstore sunscreen may do the job. Modern tires contain carbon black which is supposed to absorb the UVA/UVB and convert it to heat, before it can do much damage to the rubber. I guess you can think of carbon black as a pre-fabricated suntan.
For Ozone, I think you need to think a little bit about how ozone attacks the rubber. Ozone is a powerful oxidizing agent, I believe it is an unstable molecule with 4 free electron sites in the S and P orbitals. So, you want a chemical barrier that bonds with ozone before it reaches and oxidizes your tire. Some modern automotive tires contain compounds built into the tires that are designed to leach out over time - BUT ONLY IF THE TIRES ARE RIDDEN, NOT IF THEY ARE STORED. Any persistent liquid cover for the surface of the tire might work. However, you want something that does not react with your rubber, and Armour-All is said to react with typical rubbers :
http://www.6mt.net/
A third issue is that the rubber may leach out the oils that make it supple and long-lasting. This is because there is a gradient between the dry air and the oils in the rubber. Any material that covers the tire and moves this humidity gradient to an oil or liquid covering the tire, will leach the covering liquid, not the tire's precious oils.
My approach is to store all rubber products in sealed plastic baggies until use. I bagged all of my products as soon as they were purchased. Any diffusion gradient will eventually stabilize as some of the oils leach into the bag and reach equilibrium with the oils in the tires.
For products installed on a bike, like hoods or tires, perhaps this product would work :
http://www.microfiber-products-online.com/
Disclaimer : I don't work for these guys and have never used the product, but it is said in the article above concerning Armor-All that Meguiar makes a much higher quality (and unfortunately, more expensive) product than Armor-All.
- Don Gillies
San Diego, CA, USA