[autoavia]

Fly cars are well known for having problems with weeping tyres. There have even been problems with old stock which has never left the shop. The general opinion seems to be that it is a reaction between the tyres and the plastic base. 

 I know of some ranges of handbuilt 1/43 scale static models where the tyres split with age caused by the mix of rubber and chemicals used to mould the tyre breaking down.