Originally Posted by DeBUSK
I jack my front wheels off the ground to lube the king pins. Always. This allows the lube to cover all the pin & axle.
THAT'S the primary reason to raise the unit for greasing the front end. It has nothing to do with the "wheel bearings". That's a whole separate issue. Many times there is a "bind" on one, some, or many of the greasable components if the weight of the vehicle is left on the tires/wheels/suspension.
So, much of the time, raising it relieves the pressure on some or all of those components. By raising the coach, there is less strain on many of those components and the grease has the ability to completely coat what's needed in each and every one of them. By components I mean, King pins, tie rod ends, drag links, steering knuckles, and anything else that may be related to that front end.
Sometimes, you can do a complete lube job without the raising of the coach or front end and, all the components receive grease just fine. I've done it both ways. I have no problem taking the effort to raise the coach/front end. I can do it with the jacks or, I've got a series hydraulic jacks hanging around that will lift the frame etc. just enough to take the pressure off the system.