Originally Posted by
genejockey
Except for the fact that you need to screw it down to keep the small amount of air in the tube to give it shape when you're feeding it into the tire.
The way they did it was to glue the tubular tire on the rim, inflate it fully, and only then snap off the top nut. As long as the pressure was kept above 20 psi or so, they were able to keep riding the tire until it flatted or wore out.
You could do it with a clincher tire and inner tube, of course. But in the 1960s, there were no high-performance clincher tires on the market, so all racers rode tubulars exclusively.