Originally Posted by sivat
I was backwards. The bearing balls will actually try to unscrew the drive side. The balls act like a jockey gear to reverse the torque of the cranks on the cups. Its a little hard to picture.
I'm paraphasing Sheldon Brown here..... as he explains that it is not the bearing friction that makes them unscrew themselves, but a phenomenon called "precession".
"You can demonstrate this to yourself by performing a simple experiment. Hold a pencil loosely in one fist, and move the end of it in a circle. You will see that the pencil, as it rubs against the inside of your fist, rotates in the opposite direction."
He talks about this phenomenon with regard to pedal threads, but I think you're talking about a similar situation on a BB.