Since I always ride tubulars and since I am usually the only one riding tubulars, I carry two spares. On several occasions I've loaned another rider one of my tubulars when they've wiped out a clincher. They're always skeptical but it gets them home. In the first days of racing clinchers, they were all wire beaded so it was difficult to carry a spare. We all used to carry a tubular for a spare.
Jim Cushing-murray
Del Mar CA