Bearing Lube Systems - Fiberglass RV

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Old 05-20-2008, 09:23 PM   #1
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They are almost totally different systems with the only things in common are filling the hub with grease by means of a Zerk fitting.

Bearing Buddy is a spring-loaded grease cap on the hub. One fills the hub with grease, from the outside in, using the Zerk fitting until the hub is filled (I don't know where the air goes..). The spring keeps the hub under positive pressure, so that when a warm hub is dunked in cold water, the shrinkage won't pull in water past the seal and grease cap to contaminate the grease. There is no way for fresh grease to lubricate the inner bearings unless the seal leaks. Under hot highway conditions, expanding grease has to push the spring back or exit through the seal in older models; newer models may have pressure relief valve to prevent this. Newer BBs use a special seal to prevent overpressure, obviously requiring disassembly of the bearings to install.

BBs are also subject to loss by getting knocked off, excess tire bounce from unbalanced tires and theft, according to the BB site.

OTOH, the EZLube, AG Hub and Spindle-Lube systems have no pressurization except when pumping grease. The axle spindle is hollow and has a Zerk fitting on the outer end, covered by a rubber cap. The inner end of the spindle has holes between the inner bearing and the seal. With the rubber cover removed, fresh grease is pumped into the spindle (by hand pump, with wheel jacked up and slowly turning, according to Dexter). The grease goes down the spindle, comes out the holes, goes through both the inner and outer bearings and comes out next to the Zerk, forcing the old grease out. Once the hub is greased, if the grease expands, coming out through the rubber cap is easier than getting past the seal. (I recommend scooping out some of the excess grease under the cap to prevent grease fling, but be careful because the inner edge of the metal cap is *sharp* and fresh blood looks really strange on greasy fingers...).

With the spindle-lube systems, one can also choose to hand pack bearings in the conventional manner, esp if one doesn't like having a hub full of grease.

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Old 05-22-2008, 02:26 PM   #2
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Please pardon what is probably either a dumb question, or at least a useless one.

I know what a zerk fitting is only because I am an old man. Cars used to have such fittings long, long ago. When we old men were young men, we used to take our cars in for a "lube job" and zerk fittings were all over the underside of old Chevys. But I doubt if young men have ever seen them, because thay have gone the way of Ignition points and distributor rotors, and are no longer seen on automobiles.

I don't recall when cars went to sealed bearings, but it's not like it happened yesterday. Sealed bearings are not new or "cutting edge" technology.

Because I am an old man, I know what a brake adjustment tool looks like. That's because long, long ago, you used to have to adjust brakes.

I don't recall just when self adjusting brakes came into use, but it's been quite a while. Mid fifties? For cars, it's old hat.

Why is it, then, that trailers are stuck forever in 1954, when other wheeled vehicles have moved so far on, technology wise? Is there a law against progress for trailers?

And while I'm asking useless questions, is there a reason why someone cant make an electric disc brake?

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Old 05-22-2008, 06:18 PM   #3
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Gee Lyle, I hadn't thought of myself as old until you said you were an old man and remembered all those things. If I remember them too . . . . .
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Old 05-22-2008, 07:57 PM   #4
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Electric disk brakes would be quite a trick because the electric magnets require a brake drum to clamp to to move the shoes...

One can get hydraulic disk brakes with electronic control, just bring $$.

Actually, Zerk fittings on the spindle lube systems have only come out in the last decade, give or take a few years. BBs have had them all along.

Dexter recently came out with the oil-filled cartridge bearings, but it takes a large hub (#11 axle with six-lug hug and 16" wheel) to accomodate them. Scamps, etc, use #9 and #10 axles.

Since axles and brakes are seldom a user option (except older, small trailers), manufacturers are inclined to go with the low bidder and standardize. No real incentive for self-adjusting brakes, esp when Dexter, et al, recommend annual inspection and repack so adjusting brakes becomes part of the job anyway.
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