Thanks - I knew there woud be a simple answer.

Presumably then the tyres hold their heat for the five minutes or so they sit on the grid after the green flag lap and the tyre changes? I'm just wondering whether it's worth it (although it obvioulsy is as they do it!).

I know that looking at the used tyes in the garages, it looks as though they've almost melted, and you always see the chaps with the 'hair dryers' giving them a shave between races!