[QUOTE="Simon Atkinson"] ITYM the imaginary force we refer to as centrifugal is what sticks them to the walls. Actually (as I am sure you well know young Porl) the bike is trying to go ever higher and tiny sprinklings of fairy dust cause it to slide back down.[/QUOTE] The more I understand the more I realise how much more there is to understand and while I'm realising that I've forgotten what I understood in the first place.