Bearings: How hot is too hot?

Amazing how many questions one little weekend trip generates...

We just returned from our first outing with the TM. About a 1.5 hour trip home and temps outside in the mid 90's.

Got the trailer parked at home and about 20 minutes later decided to check the wheel hub temps. Both sides were too hot to hold on to.

Is this too hot?

I had re-greased the bearings this spring, so I'm assuming lubrication isn't the issue.

While I wasn't descending any steep grades, could it be that the heat is just from normal braking? Or maybe I have my Prodigy set to make the trailer work too hard?

Or what the heck else?

Thanks for any help...

Steve

[Bill]

Got the trailer parked at home and about 20 minutes later decided to check the wheel hub temps. Both sides were too hot to hold on to. Is this too hot?

Yes, I think it is too hot. I don't regularly check the hubs, but I do check the tire sidewalls with my fingertips at every stop. Hundreds of times, in other words. Since this check is done within seconds of stopping, I think I would have noticed if anything about the wheel assembly was so hot that even after 20 minutes, it would still be too hot to hold. I DO remember checking the temp of the metal wheels themselves after several miles of hard braking on the very steep Coronado Highway in eastern Arizona. One wheel was quite warm (but by no means hot), while the other wheel was stone cold. That's one way - and the best way! - to discover that you have had a brake failure.

So assuming there was no smoke (the sign of a stuck brake), I don't think braking is the problem. My suggestion, subject to better info from others, is either to take it to a brake shop fofr a wheel bearing inspection, or pull the wheels and the bearings and inspect them yourself.

Bill

Ditto Bill! I too checked at every stop, warm ok, hot never! Something is wrong.

[RockyMtnRay]

I actually do check the outside of the wheel hubs with an ultra accurate temperature measurement tool (the back of my fingers ) and, like Windbreaker, have found them to be warmish (maybe 10 or 20 degrees above ambient) but never anything remotely close to "hot". And that's even after a bit of braking coming into a highway rest stop.

Setting the Prodigy too high might make braking a bit jerky but should not have any effect on the running temp of the wheelbearings since it does not activate the brakes until the brake pedal is pushed.

Adjusting the trailer brakes too tightly, however, could produce enough sustained drag/heat to thoroughly heat the wheel bearings. With the wheel off the ground, the brakes should be loose enough that the wheel will spin fairly freely (i.e. several revolutions after just one good hand push) with just a bit of a dragging/scraping sound. If it almost immediately (like within a single revolution) drags to a halt...or the wheel resists being hand spun, the brakes are adjusted too tightly.

When we bought our TM and towed it home from Arkansas, the left hub remained at normal temperatures, but the right hub was hot enough that it was uncomfortable to touch. I tried the grease trick, but it didn't help. The brake was not dragging, so we came on home. (Mead, WA) When I pulled the wheel off, I noticed that the bearing was quite loose - i.e. too much end play which would let the bearing run on part of the race where it shouldn't be. Someone had not put the nut lock back on when it had been greased and the nut had backed off. I am not impressed at all with the greasing system on these axles, so I packed the bearings by hand and bought a new nut lock. Everything runs cool now. Another thing that can make the bearings run too hot is if they're adjusted too tightly - you've got to hit that happy medium where there's no end play, but they're still not too tight!

Thanks for all of the helpful replies. It's great to have the chance to do an online "survey" before you jump to conclusions...

I'm thinking maybe I've incorrectly tightened the bearing nuts. I pulled the wheels and drums when I was going over the TM after we purchased it. I thought I was following the Dexter instructions when re-installing things, but since both hubs were hot, my guess is that I did 'em both the same and they were both wrong.

I'll be having fun gettin' greasy again this week, I guess...

I'll give an update if any useful knowledge comes out of it.

Thanks,

Steve

I also check my hubs at every stop. Durning hot weather they get hot enough that you don't want to hold them very long but not hot enough to burn you. They cool off fairly quickly.

I check my hubs when I stop, they are warm but not hot enough to burn.

Hi all,

Just for laughs, I emailed Dexter Axle to see what operating temps they would onsider normal. Their response was "Normal operating temperatures of the bearings as measured outside the hub are about 140 to 175 degrees F. Temperatures in excess of 200 degrees F indicate possible lubrication or bearing problem. The normal bearing adjustment procedure is described in detail in the Dexter Operation Maintenance Service Manual under the section "Hubs, Drums & Bearings".

They also said "The heat may be caused by brake problems. If your trailer was configured with brakes please review the service manual on brakes and troubleshooting. NOTE: The drum temperatures normally run anywhere from 150 degrees to 400 degrees F and can easily exceed 600 degrees F during certain stopping conditions."

I would assume that if the brake drum gets to 400 or 600 degrees, the hub will also heat up, and probably exceed the "normal operating temperature".

Since technology gets cheaper & cheaper, I decided to order an infrared thermometer so I could "know" just what the temp is. The one I ordered will be about $30 with shipping, and I can use it for other stuff anyway (great toolbox justification, no?).

Steve

Last weekend, it was 100 to 105 degrees air temperature and I measured 135 and 145 degrees on the tires and 125 degrees on all four hubs. I was driving on the freeway at 65 MPH towing a 3326 King. All the water had been dumped, so I was not carrying a lot of cargo. Interestingly, my Envoy tires were 5 or 7 degrees warmer (150+). Measurement was with a Radio Shack IR digital thermometer.
Bob