Originally Posted by
choddo
Ok but when there are bearings, the force acting between the spiindle and the cup is transmitted through them so at least in my head the way they behave is a key element.
Yes, but the bearings are not pivoting in place (like fixed planet gears). The BB spindle rotates forward, the bearings roll along in the same direction as the spindle, only slower. Picture poor lubrication on the bearings and them beginning to freeze up; Which way is the force on them and the force they are exerting on the bearing cup? Same direction as the spindle, forward.