axle hub tempature

[E2360]

When traveling I regularly check the tire temps with an infrared thermometer but did not check hub temps since they were covered with a plastic shroud.



Shrouds are not gone, what is the usual temps of a hub (9500 lb fiver) and how much variation does one tolerate between hubs?



Thanks,

 

[jelag]

Most chassis type greases used in wheel bearings have what is called a dropping point of between 275-325*... . Dropping point is a test on the ability of a grease and when it will fail with temperature and gravity will take over and the grease will flow away... .

With that said, I'd worry if and when I would see over 200*F. I check hubs, tires, when we pull into a rest stop... . I like to see the tires below 150* and if the bearing are set right I usually don't see hub temperatures over about 125-150*... . the exception to this is if I've just used the brake coming off the freeway into the rest stop... its not uncommon to see several hundred degrees in brake drum temperature and some of this heat will migrate to the hubs and bearings on long down hill runs... Even our large work trailers rated at 22K lbs never seem to run any warmer... .

I personally don't like to see more that +- 20* per tire and about that on the hubs... . we've weighed our 5er and know that both axles support the same weight within 200 lbs... and the whole trailer is about 13K lbs... 3 on the tongue and about 5K on each axle. .

We use a synthetic grease with a dropping point of 550* in the HD Clutches we build and we buy that by the barrel... . I just scoop some of it up when the drum is empty and take it home... . that's what I pack my bearings with... ... I was taught 2 ways to deal with preload... one using a torque wrench and the other a rule of thumb..... I've used that rule of thumb over the torque wrench all these years... and we've done well with that...

Remember all grease is, is a chemical that supports and holds oil for lubrication and its only as good as its ability to handle heat, and the other things that try and invade its world. .

Most new axles have a grease fitting on the end of the axle shaft for greasing them... . we end up selling a lot of backing places and electric brake systems because of 2 things... . either the bearings get no grease, and the bearings fail, and damage the shoes and backing plate, or they over grease and all the excess is purged from the bearings into the hub, out past the seal into the drum and backing plate... . remember that the wheel seals usually only have one lip... to keep water and dirt out and will let excessive grease push out past the seal... .

 

[E2360]

JIM:



Thank you for the great responce. You answered all my questions and then some. I was warned by my rv shop about the bearing grease fittings and "too much of a good thing"



Jim

 

[WMonroe]

My 5ver is not quite as heavy (7000 lbs) as what your dealing with but here is the experience i've had recently. I have started checking my hub temps every time I take the camper out. The majority of the driving i do with it involves some stoplight/stop and go type of driving before I park it. That type of driving combined with not taking my time enough (ie. not being afraid to use the brakes) would give me hub temps between 120 and 150* depending on how hot it is outside how hard I had been on the brakes. Recently I took a longer trip and after about an 90 minutes of mostly highway driving I pulled over to check temps and found they were running about 95*.

I have began to leave more room to coast when doing stop/go type driving and this has dropped the temp a little more.

The four hubs on my camper run within 10* of each other except for when I didn't have the brakes adjusted evenly. I had one drum just a little tighter than the other three which gave me about a 25* increase in the one hub. Backed it off a few clicks and now it runs right inline with the rest.

Hope this helps some.

Will

 

[jelag]

Will brings up and excellent point... ...

Hydraulic brakes allow for the same pressure on both front wheels, or both rear wheels as the master cylinder is a 2 chamber unit... so the same pressure means the same braking force... .

On electric brakes, they are each dependent on their adjustment and how good the electrical connections are... . a loose connection at the lower voltages that they run at means lighter breaking on that axle... thus less heat. . and the wheel that is working harder will have more heat and more wear... .

We own several work trailers and one of the things we do every 6 months or so is adjust the brakes... . they don't self adjust... .

We raise the trailer and put it on jack stands, and spin each tire adjusting the brake until we get a light drag, than back the adjuster off a click or two... .

When we pull the hubs to clean and re grease the bearings we check and service the brakes...

Where the factory put the electrical wire through the axle we remove that... throw away the scotch locks... . and use a good butt connector and shrink tube... the shrink tube we use is the same tubing used on wells, it has a heat activated adhesive in the tube for a water proof connection...

 

[kschitoskey]

Checking hub temp by hand

Great advice on this thread. I don't have an IR thermometer; when we're pulling our fiver, I go around and check each hub by putting my hand on each one. Not uncomfortable to put your hand on a properly adjusted bearing (<200 degrees). If one feels particularly hot I know I have a problem.



That being said, an IR thermometer is probably cheaper than a trip to the burn unit :-laf