Originally Posted by
JonathanGennick
Can one leave the valve open when using those simple adapters? I've never done so, but I recall reading once that it was possible.
Yes, you can leave a presta valve open. A guy I used to race with was annoyed at having to unscrew the knurled bit at the top of his presta valves, so he would snap it off. As long as the tube is holding air, the presta valve won't leak.