I changed out both tubes, ones that came in bike were Kenda's made in Indonesia, switched to Bontrager's made in Taiwan, the valve quality appeared better and the rubber seemed thicker. I aired up the tire prior to riding it the night before with my Ryobi electric inflator, perhaps a small piece of particulate lodged in the valve? I've had plenty of puncture flats, and tire blow-outs never one where I couldn't find the leak.