I'm an amateur biker, but regularly bike to work. I've been having a problem with my tubes going flat when the valve tears away from the tube. Here's a (grainy) picture to demonstrate:
This is happening quite frequently. It usually happens when I am pumping up my tires, but occasionally when I'm riding.
I've tried a few things with the nut (tightening it extra tight, keeping it loose, keeping it off altogether), but this keeps happening. How can I stop this? Is there anything stupid I'm missing?