HOW HOT FOR THE TRAILER HUBS?

Here is my story/question. The spindle on my boat trailer has the grease fitting on the end which allows grease to fill the cavity between the spindle and hub (including the bearings). There is a metal cap (dust cap) with a rubber plug covering the grease fitting. This is on the outer bearing (small bearing) end of the spindle. I noticed a few weeks ago, a small amount of grease around the rubber plug on one hub. Investigation revealed the rubber had torn and water had gotten into the grease, at least on the outside between the outer bearing and the rubber plug. Inside the hub (around the bearings) didn't appear to be contaminated. However, the contaminated hub was running a little hotter than the other side. I could hold my hand on either hub, the contaminated side was just a little warmer. I disassembled, cleaned, repacked, replaced the seal, dust-cap, and rubber plug, and filled the cavity with grease. I pulled the boat down the highway at 70 mph for about 15 minutes and gave it a check. I can still hold my hand on either hub, but the newly repacked hub is still hotter than the other side. Again--I can hold my hand on either hub. My question is, how hot is too hot? Should I be concerned? I do not want to end up on the side of the highway--or worse! Any input will be appreciated. Thank you.

 

It could be several things. It could be as simple as a heavier load on the "hot" side. Also check for equal torque on both spindle nuts. That you can place your hand on the spindles says nothing major is wrong. 15 miles should show up as real hot if there was a problem.

 

If the temperature is too high, the seal will start leaking, so don't exceed 250 degF. The bearing grease can tolerate higher temps than the seal. Pennzoil 707F, for example, can operate continuously at 325 degF. http://www.pennzoil.com/wp-content/uploads/2012/02/Premium-Wheel-Bearing-707L.pdf

 

If you can still touch it, you should be ok. I would guess the nut on that side is just a bit tighter. Probably had to be to get the cotter pin in. No big deal.

 

I know on the big stuff with oil bath bearings, when you retighten the nut, you are supposed to back off a quarter turn, then put the cotter pin in.
years ago dexter had a big problem with them and they would get too hot and snap off.
recheck the nut.

 

It is a single axle trailer with a 16 ft aluminum bass boat, 40 horse 4 stroke. When I reassembled the hub, I tightened the axle nut with a wrench just a little to seat the bearings. Then I completely loosened the axle nut and re-tightened it by hand. I then backed it off enough to line up the cotter pin hole. This is how I have always done it. I just jacked both sides of the trailer and spun the wheels. They both feel the same, nice and smooth, no growl, same amount of play (virtually none). As far as I can tell, they are both identical. I think I will take it on a trip to the lake this weekend and see how it does. It is about an hours drive.

 

No trailer brakes, right?

I'd say as long as you can hold your hand on the hub you're good.

When the toll booth attendant points out the flames coming from your hubs, you're NOT good. (yes, this actually happened to me. hubs overheated due to dragging brakes)

 

usually one good way to tell is if the hub paint has burnt off. forgot about that the other day, (damn stroke)

 

found out at work that farm +utility grease gets hotter under constant load than axle grease. i always thought that they were the same. we sell belmont trailers. also we have found that the hubs get hotter when you pump them full of grease via grease buddy axles. as it fills all the void right around the spindle, until you run it a bit until the grease gets flung out to the outside of the hubs. no biggie if you can still roll the wheels wish no bad noises.

 

I checked the axle nut. When I reassembled the hub, I put the axle nut on hand tight. However, I cannot remove it by hand. I removed it with a wrench and reinstalled it by hand. Then backed it off two flats so there is a slight amount of play in the hub. Installed a new cotter pin, reassembled it all and filled it with new grease. Both hubs are now within 1 degree F of each other. Here are the results of the 70 mph, 15 minute tow:

OUTSIDE AIR; 88 F
HUB; 98 F
RIM; 94 F
TIRE (inside the treads); 107 F

I did this test several times over at different speeds and for different times. The posted results are typical of all readings. Temperature was measure with a digital thermocouple.

The bottom line is the axle nut was too tight. All seems to be working good now. Thanks for all the input.

 

I towed the boat over 1100 miles over the last week. No problems at all. I was able to hold my hands on the hubs at every fuel stop after 75 mph for hours.