The Nissan Wheel Hub and Wheel Bearings are where all the weight of the vehicle rest against. The resistance to movement by the Nissan wheel bearings has to be kept to a minimum so the use of ball bearing grease is used as a lubricant.
The wheel bearings are inserted into the hubs on all four wheels of the Nissan. They should be routinely greased during the scheduled brake maintenance when the pads and shoes are changed. If this does not occur the bearings will become dry which will cause them to heat up. When the bearings heat up in the wheel hub, they are not permitted to expand and the seizing up of them is the end result.
If the Nissan owner is carrying out their own brake job, they will have to access the bearings in order to pull the brake disc and hub off. This is accomplished by loosening of the locking nut on the spindle. Once removed the outer bearing is exposed and can be removed. With the nut put back on the spindle shaft, the edge of the nut can be used to pull the inner bearing and the spindle seal off of the back side of the brake disc. The only alternative is to remove the spindle seal with a screw driver or pry bar which can damage the metal ring holding the seal in place in the hub of the wheel.
With access to both bearings now completed, the packing of them with fresh grease has to be done then the bearings can be placed back in the wheel hubs and it mounted back on your Nissan. This is the only way to ensure the amount of resistance the wheel encounter when they are rotating is kept at a minimum.