My newly thought out theory in “answer” to the question in your second paragraph is that it does not migrate from the cavity to the bearings if not assisted. The assistance is to use the Zerk and force in more grease so that some moves to the bearings.
Does it have enough force to squeeze into the rollers as a hand or assisted pack does? I have my doubts.
Better than nothing? Yeah, I’d say so.
Sidebar. I recall walking down a sidewalk. What City and how long ago has faded. A car was parked at the curb. A bit ratty and sans a front wheel cover and hub cap. The axle nut exposed. Whoops no bearing at all up front. Only the nut and tanged washer kept the wheel on???
At one of my service station jobs, I had 40 Plymouth up on the rack for a lube. ,Major fight as it had probably not felt a grease gun for years, if at all after leaving the factory. then I got to the two u joints. or at least where they should’ve been. I called the owner over and pointed it out. As a mechanic had a stall in he building, we could not trample. but, I suggested he talk with Wayne as to new ones .
Yes, as I said, and found out 49 years ago. Too late to do an autopsy now, I can only surmise that the grease ran out of the bearings into the empty cavity between them.
With a grease gun, it does get into the roller bearings and fill them, and with the cavity full, it does stay in the bearings where its supposed to be, and heat is transferred to the packed grease in the cavity.
When the hub is full, the excess that ran through the outer bearing comes out the little bleed hole in the hub dust cap, which is where this thread began.
And perhaps as Doug suggests. A means of dealig with the grease of the day. and that the grease of a later time could be used sans packing the entire cavity.
I surely recall the Texaco product for packing wheels was “long fiber” and a lot stiffer at room temperature than the product used for lubig chassis.
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The hub is rotating and gets hot, Doug - cup stored grease would migrate, and the cup prevents the grease from leaking out…? Certainly, all bearings should be carefully packed at installation…
Needless to say; too much, or wrong grease type, is ‘not good’…
