Wheel bearings - schoolboy question

[npanne]

Gents, a really basic question:
Just about to fit new bearings into my front hubs. All the old grease has been cleared out as it was a tad gritty, when I fit the new bearings, do I need to fill the cavity between the inner and out bearings, or just pack out the bearings themselves?

[molten]

Definately Fill the cavity!

[npanne]

Fair enough. I kinda figured that it was there for a reason, just couldn't find mention of it in Haynes manual.

[nang]

Why fill the cavity please ??

[SpitNoir]

Perhaps I would define "fill" too.
For my part, I've always put a goodly amount of grease in there, but definitely never filled it up. Merely lined the walls with a thick packing.
My logic (if you can call it that!) was that it served multiple purposes. One would be to keep the surface covered with grease to keep it from rusting. Another would be to fill as much of the void as possible, to reduce the amount of water that could intrude under the extreme conditions of submersion. With utility-type vehicles (Jeeps, Broncos, Land Cruisers and such), that last was a distinct possibility.
Another very early thought of mine was that it would be partially used to "replenish" any grease that would be flung or fall out of suspension in the bearings themselves. Figuring that as things expanded and contracted due to heating and cooling cycles, and centrifugal force did it's thing when on the warm spin-cycle, new grease would somehow magically interject itself into the bearing. Keeping the grease as new and clean as possible.

Now, after all those years of "assuming" that, I actually thought about it and couldn't for the life of me figure out how that would happen in the real world. But it sounded good when I either thought about it or was told that when I was a young'un.
However, I still think it's a good space-filler to keep moisture as at-bay as possible.

Paul

[piman]

Hello Npanne,

do not fill the hub cap, about half is more than enough or else it will all leak out as the bearing warms up. Personally I wouldn't fill the cavity either, When the bearing starts working, most of the gease is thrown out anyway.

Alec