Originally Posted by recursive
I didn't state it very clearly. The difference was the atmospheric pressure. It went from 15psi to 5psi, hence the 10. The presure in the tire doesn't change at all since no air is going in or out.
Actually the pressure does change. The pressure you are reading on a tire gauge is really reading the differential pressure between atmospheric and what is in the tire. If you lower the atmospheric pressure, the differential is greater since no air is going in or out of the tire.