Axle maintenance--greasing or repacking?

TomCanada

I'm going to go ahead and ask a stupid question. Why do we need to do all this bearing maintenance craziness on these trailer axles yet we don't have to do the same on our cars?  Differences in design?  Why not do the same thing as on cars and use a design that doesn't require all this craziness? 

N7SHG_Ham

@TomCanada cost mostly. An RV is typically a low usage item and built as cheap as possible. Dexter does make some sealed units I believe and on some of their heavier axles offer an oil bath hub same as heavy duty trucks use. I also believe there at least used to be a company selling an oil bath conversion kit for lighter duty hubs. Found one option here: https://www.liqualube.com/selection.html

Car bearings are sealed (mostly) these days, however they used to use a very similar bearing set up as the Tabs and require similar regular maintenance. I know vehicles in the 60's and 70's were like that, and there was probably a mixture for a number of years, but by 2000 or so I think there were very few cars using a none sealed bearing.

In early 70's my Father had a front wheel bearing seize due to lack of maintaining the hub on a car that was about 10 years old at the time, it was major job to repair.

Mickerly

In the 60's and 70's, repacking wheel bearings was not that hard. It was time consuming to clean out all the old grease. It took technique and patience to fully pack the bearing. But this was a once every 40.000 miles or so task. Sometimes people forgot, or tried to get just a few more miles before the maintenance. That did get expensive. Now car have sealed bearings that last for the life of the car.

Car brakes typically a removable disc. In the old days it was a removable drum. The brake pads rub at the edge of the disc. The disc is designed to cool. Both, remove the heat from the hub area. The disc or drum is a separate piece that can be removed to allow servicing the brakes without doing anything to the hub and associated bearings.

Light duty Dexter trailer axils with electric brakes have a brake drum and hub assembly in a single unit of cast iron. The electric brake solenoid slides on the inside of the drum right next to the hub bearings; whenever the wheel is turning. On a utility trailer, towed at low speeds and for short distances, not too much heat builds up. Think if the lawn guy with his trailer full of mowers. We tow these trailers at a relatively high speed for many hours at a time. This brake design generates heat in the hub.

In the old days we packed wheel bearings with "wheel bearing grease". It was thick and had a high melting point. It's too thick to go through the "EZ LUB" system. So, Dexter recommends Lithium all purpose grease. For a utility trailer, this will work fine and requires no special skills or knowledge to service. Unfortunately, it has a low melting temperature. When the grease melts and leaks out, the bearing fails.

If you look at the Dexter product line, as is mentioned above, the heavier axils have better bearings and different brakes. They don't have the "EZ LUB" system so they can use better grease.

You could change the design to use hydraulic brakes and significantly reduce the heat in the hub. A cost effective method is called surge brakes. They work fine, but they need their maintenance too. And the electric brake controller has some clear advantages. It is possible to get electrically controlled hydraulic brakes. Having looked into this, it is much heavier and a very expensive upgrade.

As mentioned above, these small trailers were meant to be "low usage" items. A utility trailer axil is a good choice.

Sorry about being so long.

tabiphile

@Mickerly...yes...you nailed it. 
Having said that, you have lived charmed life. Sealed bearings on modern cars do fail and with some regularity. They will howl and growl as they go.....you'll think that a tire is on it's way out. Nope. Wheel bearing.
Some fail within the warranty period but most will wait until just after it expires. Like that water heater that leaks 2 weeks after the 10 year warranty expires, these do the same. 
Failures are most common on all wheel drive vehicles where the bearings are carrying considerable load. Generally you can expect failures to occur after 100,000 miles and earlier if your vehicle lives in a cold wet place where they use lots of salt on the roads. Or, they may last much longer.....
@TomCanada....VW bugs and old Chevy trucks taught many of us the charms of greasing wheel bearings. To this day I still grab onto the outside of a wheel and give it a tug when I'm buying a used vehicle. You can tell when the wheels are getting ready to fall off.

gulfarea

Back in the old days I sure would have loved to have the E-Z LUBE grease fitting on my 1951 Studebaker! After owning a garage for 31 years all the failed bearings I worked on including complete axle spindle wipe out occurred from dry caked grease. Sure would have been great to have that grease fitting on to shove in new grease with the oil still in the grease. Art 

Mickerly

Yes, sealed bearing can and do fail. Just like our T@Bs, heat is a cause much of the time. Also impact. Sealed bearings are not so good off road. Many modern mountain bikes are figuring this out too.

They are marketed "for the life of the car". Most of the time, they do pretty good.