New tube, out of the box. Installed, pumped up to 100 psi, trued the wheel, went to bed. Got ready to ride the next day, checked the tire, 80 psi. I had checked the tire for debris, rim for burrs, etc. prior to installing the tube. I've also noticed this on other tires/tubes as well. Where does it go? Poor tubes? Bad valve? Bad brand? Anybody else experience this?