Originally Posted by
trailangel
Checking the presta valve tightness is part of prepping the new tube before installing. You failed to do this.
+1. This is kind of a rarely talked about thing but I always tighten my presta valves when new. I learned the hard way when fixing a flat on the road with my screw on pump and unscrewed the valve removing the hose. I found out my chain tools' rectangular cutout fit the presta valve flats perfectly. This was the only time I've ever used that chain tool for anything. Check yours if you carry one as they are not all the same and may not work. Some spoke wrenches also work, not for DT nipples and some others but I can't remember which size works. They also make these little gems to carry with you and cheap.
Origin8 Presta Valve Core Remover Tool - Blue Sky Cycling Your bike shop may have them too. I should add that since I've started checking the valve tightness when new I haven't had one come loose again. Just don't get carried away with gorilla strength. A light snugging up will do.