Originally Posted by
DiabloScott
I evaluate your claim to be hooey.
I ran Presta stems in Schrader holes on my commute bike for years in all kinds of weather without a flat. I had bought some new tires that were too wide for the Schrader valve tubes that came on the bike, so I put in some properly-sized Presta valve tubes that I had in my pile. There was simply no reason to swap them out once I had them in there.
Perhaps consider usage, as there can be a lot of vibration causing a presta stem to rock wildly in a Shraeder-sized hole, which causes the failures I described.
Also, most 27" rims will be single-walled, which narrows the possible span of support of the flexing valve (depending on a lot of variables).
I've many times used my spare Presta-valved tube to do a road-side fix, but my own experience has me swapping them out for solid Shraeder valve tubes at my earliest convenience.
And again, when tightening the nut on the added thickness of a double-walled rim, the nut is "bottoming" only on the bond between valve and tube itself, and which I have many times seen fail and leak.
This sort of failure is also not entirely uncommon to Presta-drilled rims, but where the rim seems to better support the nut's tension.
It's sometimes the case that those nuts need re-tightening as the rubber yields, which may eventually end in failure.
It's also the case as you noted that Presta valves can in many instances endure mis-fitment with no problems noted between tube replacements. Many of the tubes I use also come to me having previous usage, making them less robust than new tubes would be.
But even the thick, too-long (longer than needed) Shraeder valves installed on my truck's rims regularly failed from combined smog/aging/flexing.
Whatever valve is used and whichever type is carried as a spare, be sure to have an inflation device that is configured to handle what you have!