Abstract: A bottom bracket assembly for low-speed rotation is formed of a main body having an axial hole running therethrough, a spindle inserted into the axial hole, and a pivotal assembly having a self-lubricating bearing, a bushing, and a ball valve, each of which is made of a self-lubricating material. The self-lubricating bearing is sleeved onto the spindle and located at one end of the axial hole. The ball valve includes a through hole running through an axis thereof and sleeved onto one end of the spindle relative to the self-lubricating bearing. The external diameter of the bushing is smaller than the internal diameter of the axial hole. The bushing includes a spherical bushing aperture for engagement with the ball valve to make the bushing deflected on the center of the ball valve and thus the rotation of the spindle remains stable and smooth.