Well I have an IR sensor gun that I check hub temps every time I stop. I do this on the RV as well as all three equipment trailers. I also have the Tireminder sensors for tire temps and pressure readings real time in cab. Tire air pressure which would be directly effected by hub and wheel temps as well as the tires never got above 60 deg F. The IR hub temps never rose above 94.7 degree F and that was not on the effected hub but the axle behind it.Something is wrong with the bearings on that hub causing a spike in temperature to pop the caps over and over.
They are EZ lube hubs with the rubber center caps that go into the metal grease/dust caps. If it was an air pressure effect it would blow the other rubber plugs out long before the metal caps would be shed.I think ruffdog could be onto something here. Check bearing temperature after several miles, and see if it's abnormally high. If not, the only explanation I can imagine is that there's just not enough air space (eg. too much grease), causing abnormally high pressure for the small expected temperature rise.
OP didn't state if these were EZ Lube, Bearing Buddy, or any other specialized system, so guessing just regular old hand-packed bearings. EZ Lube usually has rubber caps that fit inside the stamped steel hammer-ons, and bearing buddies usually have rubber condoms that go over a machined steel hammer-on.
Regular old stamped steel grease caps aren't vented. Usually not an issue.
The hub temps are within 2-3 degree F of each other whether it is a 1 hour drive or a 5 hour driveI think this is a bit more common than some think. While it is possible to get bearings too tight and experience heat build-up, lubricants do expand as they get warmer and with no place to go except around seals and the cap, they can push the cap off. And like others in this thread, I have simply drilled a small hole in the cap to relieve pressure. Perhaps a short test drive, reach down and feel the hubs on both sides. If one is much hotter than the other, pull it apart and see what the real problem is. If the same, try the 1/16" hole approach. Cheap solution.
Agreed. This is weird. Just to be clear, you're saying these are EZ Lubes, with the usual rubber center plug in the cap, but you're losing the steel stamped housings that hold the rubber caps?They are EZ lube hubs with the rubber center caps that go into the metal grease/dust caps. If it was an air pressure effect it would blow the other rubber plugs out long before the metal caps would be shed.
I've lost the grease cups off of my Haulin trailer (little 8x5.70 tires). I think I probably scraped them off on bollards. Whether that is possible in the OP's case would depend on whether the grease caps are wider than the tires.may not look pretty, but my caps never fit some of my trailers well, I simply wrapped electrical tape around the hub and the cap, and the issue never came back.
Totally different subject, but back in the 1980's, the OD of Bearing Buddies was an exact match for the ID of a 12 oz. Coca Cola can. Saltwater boaters used to hose clamp fresh soda cans over their bearing buddies each season, easily replaceable dirt and water shield, sort of belt + suspenders.I've lost the grease cups off of my Haulin trailer (little 8x5.70 tires). I think I probably scraped them off on bollards. Whether that is possible in the OP's case would depend on whether the grease caps are wider than the tires.
I had hunted for replacement caps at auto parts stores and they didn't have any. I think trailer caps may be different than auto caps. So, soda cans and electrical tape was it. I've had those on the trailer for an awfully long time, and they've served me well.