Servicing Trailer Bearings
I, personally, recommend at least a yearly service of the wheel bearings, more often for severe service or high mileage units. Trailer bearings should be repacked every year because they are subject to conditions that automotive wheel bearings are not. A trailer typically sits for many months in storage, allowing possible moisture infiltration through condensation. It is this moisture that can most damage the bearing surfaces. By repacking your bearings before the camping season, you virtually eliminate this problem.
This schedule of service does two things:
a) It allows you to keep an eye out for brake lining wear, bad seal conditions or other problems.
b) It gives you peace of mind as you "thunder down the highway".
The bearings, when properly adjusted, should not generate any noticeable heat. The trailer brakes stop the trailer by converting the momentum of the trailer into heat energy through the friction between the brake shoes and the brake drums. This would be the heat that you feel at the hubs and is transferred there by the brake drum, itself.
Just a short (true) story here to illustrate ... The other day, a couple pulled in with a 25 foot fiver - they were on the road and halfway through a 6000 mile trip. For reasons too long to describe here, they suspected a wheel bearing problem, and asked us to inspect/service the bearings.
Upon pulling the first wheel, I noticed the brake drum and lining had surface rust on them. So did the other three - these brakes had not been working for a long time! (We are located in the middle of several mountain ranges here!) After the bearing re-pack, I traced the brake problem to a bad connection on the trucks brake control unit. The truck brakes, alone, had been stopping the combined weight of this rig for 3000 miles.
I suggested to the owner to have the truck brakes inspected, also. Our mechanical department found the truck brakes in very bad condition, with the linings and pads virtually crystallized and falling apart in chunks.
In other words, this was a disaster just waiting for the next ten or twenty miles to happen. While not a bearing related problem, as such, it was the bearing inspection that discovered this situation.
Once a year bearing service, is not too high a price to pay!
See also: Servicing Trailer Bearings
See also: Adjusting Trailer Brakes