oil cooled bearings

[MagikSmallie]

I didn't think there were caps, I thought the hubs were sealed. I know there is a way to refill and check but you have to remove the wheel first right?

[dc chopper]

no, there is a small cap in the center, pop that out and add oil. Some of them even have add marks that you see without taking caps off and that eliminates sticking your fingers in to check the level. The only issue there might be is 1: the gasket behind the cap can leak but that is very rare, even on semi's ( I drive one) and 2: every now and then one might crack, a rock wont crack it something extraordinary has to occour for that.

[artcarney_agr]

I didn't think there were caps, I thought the hubs were sealed. I know there is a way to refill and check but you have to remove the wheel first right?

Most have a clear viewing window for visually checking the fluid level, or for water coming in (oil will be milky if water is in it).

The filler is a tapped plug in the hub. You have to pull the tire off to add oil.

It's true that semis have used the technology for years, and it has worked well for them. The difference between semis and boat trailers is the water factor.

With grease hubs, if you have a problem on a trip, it's nothing to drop into a Tractor Supply, Auto Zone, O'Reilly, or similar type store to get what you need to get back on the road. If you have oil bath hubs, you better have a good supply of parts on you, because those usually have to be ordered....