Rubber tires

One of the gnarly features that sets theawesome original Transformersapart from theweak and lame modern Transformersis thata great many of themfeaturedrubber tires.

Rubber tires on a real vehicle provide cushioning and friction to its wheels as well as insulation against lightning strikes fromShrapnel;A Plague of Insecticonson aTransformerstoy,they are usually ornamental shells over the wheels, though they do roll nicely on the table, and on some toys (such as thePowerdasherswith theirpull-back motors) they serve mechanical purposes. In most cases, they are not actually rubber, butPVC plastic,which has been plasticized to improve its flexibility.

The plasticizers used can break down over time, causing the plastic to become harder. Furthermore, the plastic shrinks as this happens, causing the cracks and splits sometimes seen in those cool rubber-tired toys.