Trailer Hub Maintenance for the Hopeless! . . . . .

[Charles Brennan]

I have had far more than my share of catastrophic hub failures over the years.   
Like this one from a BEER Cruise in 2013.
Saw the wheel wobble in the side view mirror and barely had enough time to get off the road, before the wheel tried to leave for greener pastures.   
Any time you see a trailer spindle that looks rusty instead of greasy, you know you've had heat and lubrication issues.
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All that banging around at Interstate speeds isn't good for the hub, either.
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And you thought that spindle only looked like a horror show viewed from the front!!   
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My original hub problems for years and years, were due to over-loading the equipment, to the tune of 150%.
Going from a 2000 pound undercarriage to a 3750 pound undercarriage to match my verified total weight of 2800 pounds, did wonders.
But I STILL had intermittent failures, from time to time.   
Discovered that I was checking my gear to death.

Many things on a trailer hub are a friction/displacement fit.
Things like:
Lug nuts.
Dust caps/Bearing Buddies
Bearing races
Inner seals.

By trying to be proactive and take everything apart for visual inspection on every major trip, I was wearing stuff out prematurely.
See how the lug nut at right is missing half it's crown, to hold tight against the wheel, compared to the new one at left?
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When they can no longer provide a sufficient friction fit even when torqued to specification, it starts doing stuff like this to your hub studs
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And does this to your wheels:
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So as much as possible, DON'T take stuff apart any more often than you need to.
Jacking up the axle on one side, spinning the wheel and listening (as well as rocking the wheel side-to-side to check for play) will tell you more about your wheel's health than CDO visual inspections, until you've killed your equipment.

Quick exploded view for a common vocabulary:
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The Achilles Heel of trailer tires is the double lip inner seal.   
The inner seal flakes out, then grease leaks out and the next thing you know, your axle looks like the one at the beginning of this post.
The simple reason for this is axle rust.
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Salt water gets on the axle spindle, makes rusty scale and then the rust scale abrades and eats the inner seal.
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Once that inner seal gets sufficiently chewed up, it's only a matter of time before the hub needs maintenance/repair.

All is not hopeless, however.   
Emery paper in a coarse enough grit (I like 80 grit) to shine up and smooth the spindle, is where you start.
Pay especial attention to that spindle shoulder, since that's what the inner seal rests on.
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Now, how to prevent rust scale build-up from reaching the inner seal?   
This guy.
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That is a Neoprene O-ring from a scuba tank cylinder tank valve seal.
When they do annual maintenance on scuba tanks, that gets replaced.
If you're on good terms with your local scuba shop, they're happy to give you all the used ones.
If not on good terms with them, they're still happy to sell some to you.

Apply some grease to the O-ring and put it on the shoulder of the axle spindle, right before you mount the hub assembly.
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This pic may show it a little better.
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The rubber O-ring does not spin, but is motionless on the spindle shoulder.
The inner seal which is spinning, rubs against the O-ring, rubber-to-rubber.
Since the O-ring is effectively sealing off the spindle from oxygen, no rust forms underneath the O-ring.
Rust scale on the other side of the O-ring can still form, but it does not reach the inner seal, because the O-ring is in the way.
The O-ring will eventually wear out, but the Prudent Trailer Sailor will install two of them, so when the first one flakes out, the second one takes up the slack.

The next thing that causes trailer hub problems is reproducible hub tightness.
This is unfortunately, prone to folk-lore and superstition.   

Side-to-side play:
How much? None? ¼-inch? ¼-inch forward and back, or ¼-inch in total?   
Hub nut tightness:
The shade tree mechanic formula is "finger tight".
"Finger tight" for who?  King Kong, or Edgar Milquetoast?   
"Finger tight" when you have the flu, or "finger tight" when you've just eaten your Wheaties?
Way too subjective for me.

Fortunately, this actually is reproducible and independent of your strength, versus your neighbor's strength.   
1) Install all bearing races inner and outer.
2) Grease all bearings.
3) Install the the inner bearing and the inner seal on the inside of the hub and then place the hub onto the axle.
4) Install the outer bearing, outer washer, and hub castle nut.
5) Torque the hub nut clockwise to around 100 ft/lb.  The wheel should not be able to be turned.
The reason for doing this is to seat the races and bearings, so no further movement inside the hub is possible.
6)  Back the hub nut off until loosened.  You may have to rock the wheel to accomplish this.
7) Torque the hub nut to exactly 50 ft/lb.  (Wheel is again stuck shut.)
8 ) Using the end of your torque wrench as a reference, back the hub castle nut off counterclockwise EXACTLY 90º PLUS counter-clockwise to the next open notch on the hub castle nut, if not already lined up.
9) Install cotter pin through castle hub nut spindle holes.
10) Check for play.  You will find it where all the shade tree mechanics say it should be: "A little loose, but not too loose."
11) Install Bearing Buddies and grease zerk fitting
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And once again, lets' address the Old Wive's Tale  about aggressive grease guns blowing out inner seals.
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Once the grease forces the internal piston plate of the Bearing Buddy out far enough, any more grease simply comes out through the over flow port.

OR: Install EZ-Lube metal dust cap and grease zerk fitting.  Install EZ-Lube rubber cap insert into the metal dust cap.
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This is now an accurately reproducible procedure:
Torque to 50 ft/lb. then 90º counter-clockwise, plus counter-clockwise to the next open cotter pin hole, if necessary.

And to double-check this on the road:
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One of these gadgets.

Measure hub and tire temps before you leave the driveway and every time you stop, or after every hour or so.
Typically tire temps are around 20ºF above the ambient temperatures.
(e.g. 80ºF day, tire temps read 100ºF)
Hub temps (if your rig is not significantly over-loaded) will typically be 10-15ºF above ambient temps.
If one hub is noticeably warmer than the other, experiment with going up or down to the next castle nut notch, but make no assumptions; MEASURE.
I've tried loosening the castle nut to the next notch and had it get hotter, as well as tightening to the next notch and had it get cooler.   

All the learned shade tree mechanics will tell you to just "feel the hubs."   
Bad Move.
Yeah, I used to be a "hub-feeler" too, until I did the arithmetic.   
The average Human Being can only handle around 120ºF up to maybe 135ºF of heat.  That is generally accepted as the point at which you can touch a hot surface, but not leave your hand there.
OSHA further defines maximum skin temperature tolerance at 140º at 5 seconds exposure.
For a personal reference point,  I can handle touching 135ºF, but 140ºF hurts.

Depending on the type of wheel bearing grease, most of them break down at 500ºF to 600ºF. 
Try to touch that and you're going to leave fingerprints behind.
So the subjective numbers of the hub-feelers, don't really mean anything.
An imminent grease break-down is going to be HOT and well past anything a human hand can deal with.
Invest in the laser thermometer.

Brennan's Number Dictum:
If You Can Put A Number On It, It's Science; If You Can't Put A Number On It, It's VooDoo!   

Hope this helps,
Charles Brennan

[Ed]

Thanks Charles, just what I needed.