I have been commuting to work and everywhere on a Schwinn 5th Ave since the beginning of March.. Ive fallen in love with almost every aspect of it.. However im running into a problem with my back tire. Granted I have just used regular grade tubes.. but since March 1 I have now blown 6 back tire tubes.. Most of those are easily contributed to hardy thorns or glass ive picked up from the side of the road/patches of sand (I live in NW Florida).. But today after visiting the bike shop for a replacement tube I return home in a relatively good mood. Until I was walking past my living room where i keep the bike and heard a hissing sound.. walked toward the bike and realized that in the matter of about 5 seconds while sitting untouched by everything but the tile floor my back tire had lost all of its air.. it sounded like it came from the valve. Now I know that im due a new tire and had planned on buying a heavy duty set in a few days after i get paid to deter flats caused by road debris.. but it seems a bit odd that i would lose so much air pressure so quickly and while not doing anything 8 hours after the new tube had been put on.. Any idea what may have caused this/how to prevent it from happening again later down the road?