Originally Posted by Big Jim:
As far as the truck goes, it could very well be a chemical reaction from the tires. I have seen many a model car tire melt into hard plastic.
Just as an aside, I have a Lionel flatcar with a diecast combine with rubber tires on it (combine came with the car from Lionel), and they have a piece of thin clear plastic (like model "windows" are made from) set below the tires. I've seen this on other Lionel cars with similar loads. This is apparently necessary to prevent adverse chemical reactions between the rubber tires and the plastic flatcar deck.
