1974, Del Mar California. I had ridden my PX10 on sewups for three years with no problems. Even went on two different week long tours. But I was always wary of those tires, sure I had replaced a couple that had flatted. That day I had mounted two new Clement DelMondo (real silk) tires and was feeling good and fast. About two blocks from my house I ran over something and front and back both were going around shew shew shew. I walked back to the house and threw my bike down in disgust. Those tires were $20 each! That was half my months rent, gone. When I went home on vacation I had Jacques build me a new pair of clincher wheels with Phil Wood hubs and Super Champion rims. Those wheels are still going strong.
(Note: dates in this story may have drifted in the 40+ years. But the emotion of two flats at once lives on)