Was changing my commuter’s tires and when I pumped up the the tube with the other set of tires, air was leaking pretty bad! How unlucky! I felt the underside of the current tires but nothing was found… Searched the old tire and found a nasty looking torn:

Apparently, this torn had already penetrated the tube. but because it was such a snag fit no air was leaking previously! Until I pulled out the tire, the torn dislodged itself against the tube. Strong tires or strong tubes? Anyway with no spare tube insight, I decided to leave my bike like this:


And I went home to patch the tube and fix it out the next day, cheers.