Originally Posted by
Kontact
The cups self tighten because the ball bearings act like a sun and planetary gear system.
But we don't rely on this effect to set or maintain the bearing adjustment. It mainly helps keep the fixed cup from loosening.
And if the bearing seize, they go from the nice planetary Kontact gave us to a locked system that promptly unscrews cup. So keep your bearings lubed. (Pedal bearings can do the same and unscrew the pedal.)