Should I store greasy tires separately?
I really expected someone with chemistry leanings to explain to us what was "migrating" out of the rubber with time or temperature, to make them "greasy"...much like cocoa butter will migrate outside of M&amp;M's that have gotten too hot in their package.  

The question "chicks" linked to gives some good answers though, and it's encouraging that no one has had any storage tragedies.  Still, I would advise keeping them out of the usual culprits though:  sunlight and hot temperatures.