Pattern was found here: http://www.craftster.org/forum/index.php?topic=334739.0
Got a flat tyre on my car yesterday, dad had to come get me. We brought both the flat tyre and the extra one back home (no air in any of them...) and when he filled them up there was nothing wrong with the flat one. It's the tyre valve that's the problem, if you bend it in one direction it leaks... So I must have been really unlucky..!