Does TYRESAFE* block the valve stem from the inside when air pressure is released?
No (note: some vehicles operate at 50% tyre pressure in the desert to effect increased traction for rising up gradients). If the valve stem is placed at 12 oclock, this would not occur since the physical position of the valve stem will be farthest from the TYRESAFE reservoir. Most large vehicles use tyres with high walls and this is unlikely to occur even with the valve stem at 6 oclock.