The wheel bearings are a very important part of the trailer. There are a number of ways to shortcut servicing them. There is controversy about how often they should be re-packed.
I decided some time ago to develop my own schedule for this, as I have done with other mechanical procedures, like fuel filters, oil changes, tire rotations, etc.
Like any other mechanical system, you can go deeper and deeper into the minutia of the procedure and make your own decisions about what is adequate. I tend to not trust others to work on my stuff, and I want to see just what is going on in there, predict when things might fail, see how others have done their work, and just sort of own the quality of the job myself. This allows me to develop my own maintenance schedule over time and to be as confident as possible about the reliability. I don't want to wonder about the bearings, and I don't want to work on them more than necessary.
Yes, it sucks to get so dirty and end up with dirty solvents and greasy trash in the process, but it's a price I'm willing to pay to know how the bearings are doing.
So, I'm in the middle of doing my bearings right now. I'm finishing up on the third wheel of my tandem 5200 axles.
Dexter recommends servicing them at 12,000 miles or once a year, but I don't know how well they were done by the factory, so I'm doing them at 5,000 miles to get started with my schedule. These are not Dexter parts, but the drums, backing plates, bearings and seals are all interchangeable across the industry in the 5200 lb size. It may not be a good idea to assume the factory does things right, and I'm glad I'm servicing it now. We don't know the quality of the bearings, the type of grease used or the workmanship of the mechanic. So let's find out.
The first two wheels were somewhat loose and I could feel play in the bearings. I have two sets of spare bearings, dust caps and seals that came with the trailer from the factory. They are SKF bearings marked as from Germany. Good. If they are not counterfeit, they are excellent. The grease, which I don't know what brand it is, was blue, and synthetic from what I can tell. The grease that was actually running in the bearings, was all black with metal. One of the wheels was put on with what seems to be a large glob of grease outside the seal that flew out onto the magnet, the back of the shoes and a bit onto the brake material. The rollers and the races looked perfect. Still had the uniform honing marks in the races with no heat discoloration, or flaking hard surface. The rollers are all bright and shiny. They were cleaned, all old grease removed from the hubs, new Red and Tacky grease packed and re-installed with new seals and new cotter pins. I have a large arbor press to set the seals and I made a new driver to install the dust caps without hammering on them.
The third bearing was way too tight. The nut, after 5,000 miles was hard to get off with a large channel-lock plier. Way too tight. The outer race shows some wear. There was rust between the inner race and the spindle. And the grease had much more black in it than the other two. So I am very glad I am doing this service to establish a baseline and adjust all bearings correctly.
I have also looked at the markings on the bearings. They are a brand I have not heard of, YXHT, with no country of origin. The seals have no mark on them at all, but do have the banding spring around the seal and a ground outer diameter. They were not glued in, as Dexter does, so they came out with little drama. But ruined, of course. That's fine as I don't re-use seals.
So now it's on to the fourth wheel and finish up today. In the process I'm inspecting and adjusting the
brakes, which should always be done during a re-pack. Out of adjustment
brakes gradually get weaker and weaker in performance. BTW, if grease gets onto the shoes, in any significant amount, it will begin to make that brake grab. This can be felt as the trailer pulling to one side. If the right side brake is grabby, it pulls the tongue to the right, which steers the tow to the left. Eventually, the grabbing brake will begin to skid that tire on even mild brake applications and ruin the tire.
Once I'm done with this service, which will be better than from the factory and uniform in adjustment, I can begin to monitor their temperature on a trip. When they seem to be running fine, I'll go to the 12,000 miles interval. After that, if everything looks fine, I'll double the mileage to the next service. This way I'm maximizing the chance of success and minimizing the number of times I have to do it. The machine serves me, instead of me serving the machine, I'm not cutting any corners, and I'm not paying the price for poor workmanship by someone who cares less about it than me and is in a hurry.
A much quicker way to do this would be to simply pound the seal out by hammering against the inner bearing. Then force new grease into the bearings without cleaning or inspecting them, then hammering a new seal in with a hammer and reinstalling the the drum. It can even be done without removing the wheel from the drum, but that is much more likely to damage the seal. In a busy shop, this procedure would likely be given to the lowest man on the totem pole and who was being paid by the hour to get it done as soon as possible. That is certainly not always the case, but it's never the case in my shop. So saving the cost of having it done by others is not my motivation. Knowing exactly what is going on in there and doing it the best I can, is my goal.
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