No, gauge measure "0" because pressure is a differential measure, it measure a pressure AGAINST another pressure. 0 Kpa ,Psi,Bar, just mean that the two pressures are equal, this can mean that the tire is punctured or that just there is the same pressure, and the tire is still sealed tight. I think a lot of people get confused here. So, when your gauge measure a pressure of 1 bar. that is 1 Kg/sqcm ... (thats quite a lot of pressure already), OVER the environmental pressure.