[QUOTE] IMO it's the sprung goodies inside these contraptions that are causing the valve to be opened and deflate the tyre. When you think about it, all the innards are forced to the rim-side of the wheel, in the same direction you push a tyre valve to release pressure. If they are sitting against the valve it's bound to open and deflate. I should imagine there's sufficient inertia created to do this on a modern motorcycle.[/QUOTE] The ones we have are designed to push in the valve end - otherwise they wouldnt work. The device then holds the pressure so the inertia shouldnt make any difference IYSWIM