Originally Posted by
Sactown_Albert
You can purchase Presta valve tubes with a stepped nut that allow for their use on a Schrader drilled rim. The above pictures show them up close. Here are two shots with them in use. One with it unscrewed a little and one with it screwed all the way down.
Unscrewed to show Schrader hole.
Engaged so that Presta valve can be safely used.
I can see how the step could help with stem support even without much in the way of tightening tension applied.
The neat thing is that these nuts work just as perfectly with all-Presta rims/tubes, even puts less in the way of scratches on the visible face of the rim if you were to forego using nuts later on. And I've seen lighter-weight alloy versions of these as well, maybe helps with the balance factor as tube stems have grown in weight as they've become longer.
It's always good to check the rim's valve hole for sharp edges, unless as I mentioned earlier a Presta-holed rim tape is really well-centered above the hole.
I've noticed over the years that thorn-proof Presta tubes tend to lose valve stems much more frequently, was an extremely common issue at the last shop where I worked. Gotta be more delicate with the pump head and hope that the stem gets at least some support at the rim with those.