Hello people, Another noob question follows. Recently, I experienced the following phenomenon twice: I parked the bike, and after coming to pick it up 8 - 24 hours later, the front tire had practically gone flat. The funny thing is, the tube doesn't have a puncture anywhere. I took the tube out, pumped it, and there was no apparent loss anywhere. ...So... what gives? The first time this happened, I checked the back tire, and as soon as I took the protective cap off, the tire just instantly started losing pressure right in front of my eyes, as if I was pressing the valve ! I pumped both tires, rode for 30km, no problem. But this has left me puzzled. Does it have to do with the cold? Is the tire valve messed up? FWIW, I'm using swabble 700 x 23 ~ 28 tubes, both front and rear. Any help appreciated!