Monday, May 28, 2012 at 10:34
From my background as a mechanic, I have seen alot of discussion, and missunderstanding regarding wheel bearings in both trailers and caravans.
As they often sit for prolonged periods of use, and are used occasionally, time can go by and the owner forgets that its been quite a few years since they were last looked at.
Worst case, the grease has dried out, and you only have the wax paste with little oil, or lubricating properties in it.
Or its been subject to water and has rusted.
Ok, normal wheel bearing service in a car is around 20 to 40 000 depending on the make, but is often neglected,a nd thus full bearing replacement was often the only way forward.
So you can begin to see that some trailers are way over serviced to their car that tows them, and can be neglected.
Often the cause of failure.
So if the grease is still fresh, free of contamininates and good for use lets move onto the adjustment of them.
Most often, it was taught to wind up
the nut tight to "seat" the bearings, ie make sure any grease that was cusioning the bearings when first packed and assembled was not going to give you a false feeling of tightness.
And then back off, spin hub, and then nip up to either minimal slop to the first nut flat to allow for the split pin, or some said to tighten up and preload the bearing to the next flat for the split pin.
Some trailers have only
the nut and its 6 sided, so there is quite a range between each flat of
the nut to enable the split pin to secure
the nut.
In some cases, its far better to have some movement in the bearing, than tighten up further to the next flat and overtighten the bearing with too much preload.
Just this can give different hub bearing temps.
Also slight brake drag can give differing temps, as
well as previously mentioned weights.
Some bearings have a locking collar for the split pin that fits over
the nut, enabling more accurate setting of
the nut.
Some bearings are designed for a certain amount of preload, where as others are ok with some slight movement.
Ideally, just tight enough to take out any movement, with minimal preload is the best rule of thumb for most if you dont have the specific specs available to you for your make and model.
Ok, now for how much heat is too much.
Bearings will get warm/ hot, its just a fact that they will.
What is normal operating temp?
Rule of thumb, is that if its too hot to touch for more than 5 seconds, its near or over 50degC.
Up to that is pretty much ok, Thats pretty much the hottest you want it to get, and to some, that feels too hot, if its radiating heat, and burns you as soon as you touch it, its too hot.
yeah, real scientific I know, but you will get warm to hot bearings, and there designed to run warm.
Hope this helps clear up some
grey areas of wheel bearings :).
Trains
Ps, remember that front wheel bearings in cars often operate at much higher temps due to the heat soak from the disc rotor, or drum.
Thus in the early days when disc brakes arrived, high temp wheel bearing grease was required, pretty much all wheel bearing grease is high temp rated now, at least in the auto scene.
AnswerID:
486978