Deep Freud Moors:

Jose Rizal wrote in message
link.net...
Deep Freud Moors:

With regards to your bearings, if they are well packed with grease,
getting
water in should not be a big problem. The primary purpose of the grease
is
not lubrication, but to keep dirt and water out.

Not true. In bearings the primary purpose of grease is lubrication.
The primary purpose of seals is keeping water and dirt out.

Yes true. Grease is grease, and not designed as a lubricant. Oil is designed
as a lubricant, grease is not. It does treat the metal surfaces to a degree,
but any lubricating effect disappears quickly.

And where did you get this little gem of a myth from? You may think you
have a new contrary insight into something that's been established by
tribology science hundreds of years ago, but I think you're just making
it up. Read any basic tribology book.

When you pack your bearings with grease, it gets pushed out of the way of
the bearings after a couple of turns, and does not return due to its
viscosity.

So why do you think your bearings remain lubricated when only grease is
ever applied by the manufacturer/mechanic?

Grease consists of oil and carrier compound. The carrier is thick and
while the bulk of it may be pushed out of the way of the bearing/race
interface, the oil remains between the contact patch and the carrier/oil
compound which stays around the path ensures a steady supply of
lubricant.

The driest part of the bearing assembly is usually the surface
where the bearings run.

Please. The bearing/race contact path is not in fact dry, but
lubricated with a thin film provided by the grease. Even with a
tremendous load the film remains; the only way to eliminate the
lubricant is to wash it away with solvent or stop replenishing it, in
which case it may dry up eventually. Grease ensures adequate lubricant
supply for a longer time than mere oil.

Whilst that surface is clean, there are no probs.
Basic wheels nowadays are not sealed either, but have donut-shaped little
caps, which are designed to work in conjunction with the grease to keep dirt
and water out.

Grease as water and dirt barrier is a secondary characteristic, not
primary. Grease in fact attracts dirt. It's not a substitute for
seals. If it were so, seals for bearings or any rotating machinery will
not be necessary.