Sunday Review: RV Wheel Bearings Explained - Guest Post by Dale Constantine

I previously made a post on a Sunday Review about a quick and dirty path to greasing your wheel bearings. As it turns out, I was grossly misinformed! While the "cheat" works if you are in a pinch (and got us across mountains and a couple thousand kilometres when we had no other choice), it is definitely not recommended and is very risky. I will be doing a complete service of my bearings this year before moving to my next destination. Proper wheel bearing service is a necessity for travel trailers and 5th wheels.

So here to correct me is licensed automotive technician Dale Constantine, whom you can find on LinkedIn. This post is an explanation of the wheel bearings. Next Sunday's post will explain why you should never cheat!

Dale:

Ask any RVer about wheel bearings and you will get as many different responses as the number of people you talk to. But all will agree that they are important, need to be serviced, and having problems with them on the road is very expensive. Probe a little further than that and everything starts to get confusing. Let's see if we can clear up a few things.

The wheel bearings are the items inside the wheel hub - that's the part that the wheel and tire assembly bolts to - that allow the tire assembly to rotate. There are two bearings per hub and they are tapered by design. There are many types of bearings, for the taper allows for good load support as well as side load holding ability.

As mentioned, there are two bearings per hub; a larger one and a smaller one. The smaller on is on the outside. There is an outer cap, adjustment nut, washer, two bearings, and a grease seal; all are lubricated by some sort of grease. Without proper, clean and dry grease, these bearings will fail! Crazy to think something as simple as grease can stop metal from becoming molten.

Most RV owners know they need to service these bearings to avoid... that... from happening. Why don't you need to do this with your car? If we treated our cars like our trailers we would need to service them more often. Most front wheel drive vehicles have a bearing setup in their rear wheels similar to an RV, except the the ones in the car are considerably smaller due to the lighter load.

So why do these RV bearings need our attention? Think about it this way: most RVs are stored in open fields and parking lots with a much greater load resting on the bearings. Once a year we hook up to take it to camp, then we hook it up once more and return it to storage to be liberated again next year. Not that much use.

But the RV sits there all year in the weather and wind. The trailer rocks back and forth on the bearings, squeezing the lubrication out from the bearing roller and race, eventually scarring the bearing race. Then the grease - depending on the type - will have the oil "drop" out over time, leaving only the thickener behind.

And let's not forget about the presence of moisture. After even a few months, rust will be present in the bearing, and of course this leads to failure. Just ask anyone with a boat trailer. Every time that trailer enters the water to load or off load, those bearings need service or you are just asking for failure. Bearing quality plays a small part in bearing failures, but even the best bearing will not stand up to how we treat them.

Dale Constantine is a journeyman automotive technician. He does Dale's Reliability Rant every Tuesday. You can find him on LinkedIn.