Originally Posted by
brandini
I have just killed a tube because my main source of air is a (large-ish) mini pump. it failed during pumping right around the valve stem base probably from me not being able to keep the head of the pump still enough while pumping.
That's why most presta tubes have a nut on the valve stem, although many people toss them when they install the tube. By threading the nut down to the rim, the stem is stabilized so the base won't tear out of the tube.