This has definitely gotten me out of a jam before. If you aren't anticipating having the valve close up on you the valve extender itself is pretty much the only thing you're guaranteed to have around that even has a prayer of temporarily fixing the problem.

Pro tip (if it hasn't been mentioned already): if you are using a tire that doesn't have a removable valve core, unscrew the tiny nut all the way and put some thread locking compound on it (i.e loctite). If you don't have loctite you can just crush it with some pliers. Think about it...you want it to stay open. Do what you have to to make it stay open permanently--it will save you a lot of heartache on race morning (because per Murphy's law that will most likely be the first time this problem would otherwise reveal itself to you).

edit to add emphasis.

---

__________________________

I tweet!