Trailer Bearing Failure Big Time!

[old Jack]

It could be that the bearings were over-tightened, and thus overheated, causing the grease to go black. But whatever, new bearings are needed on the red side. I assume that the red grease was supplied by the brake shop.

If the bearing was overheating then the surface of the cup would have changed colour slightly. You can see that the cup has circumferential scoring as do the fillers in to cone.
This is classic lose wheel bearing witness marks as is the change in grease colour.

OJ.

[Morville]

I am usually quite pedantic about getting wheel bearings with no preload but also with no free play. It can be quite difficult with only six positions per turn of the nut. Some trailers have a cross cotter pin hole in the stub which gives 12 positions per turn, giving more precision. Our camper only has the one hole in the stub and I have considered drilling a cross hole. Since owning the camper I have made a variety of thin sheetmetal shims of various thickness to fit on the stub behind the nut to be selected so the nut can be tightened to just a whisker past fingertight to the next pin hole.
Peter

[old Jack]

Morville is right to be pedantic, trailer and caravan bearings are a common failure on country trips because they are a neglected essential maintenance items.

I have seen wheel bearing grease cook and wheel bearings turn blue from overheating after a few hundred kms of the parking brake being left on and then the trailer towed at 90-95kph.

Some further ready from Timken about bearing tightening procedures, it is 20 pages long but the first 6 pages are the most relevent to single row tapered roller bearings that trailers use.

https://www.timken.com/wp-content/up...Brochure-1.pdf item.

The above link emphasizes the high degree of skill and feel it takes to manually tighten a bearing correctly. It cannot be done with the wheel off the hub!

Sharkcaver is correct to highlight my tightening of the axle nut to align the split pin hole rather than loosen the nut after determining the correct amount of drag and bearing end float. I would do this only if the tightening would be less of a compromise than loosen the nut to align the split pin hole.
Even better is Morville's practice of using a shim washer to get it perfect.

Always replace the cup and cone as matched pair.

When removing and insert cups always heat the wheel hub up so the cups come out and insert easier.

Never use a hardened steel punch to insert the cups as this can cause the cup to crack or chip.

I get the old cup and grind the outer surface down where it contacts the hub so as to reduce the outside diameter. I then use this cup as an insertion tool when fitting the new cup, using a press is the best method but you can get away with tapping the cup in as long as you make sure this is done evenly and gradually. Again it it is best to heat the hub up, I use an electric heat gun for this and you only need to get the hubs up to about 150C. Caution you will need to use leather gloves to handle the hot hub.

OJ.

[nvll.mrrs]

Trailer bearings

I agree, was told once by an older mechanic to never dunk the hubs in the water when hot. The air in the hub has expanded with heat and when it cools suddenly it can only do one thing while under water when suddenly cooling, suck in water and if it's salt water even worse. Grease and water don't work to well together. When I trailed a boat I checked the hubs 6 monthly. No axle seal no matter how good can stop this happening. You must stop and let things cool down or get caps with grease nipples on and pump in marine grease till it comes out the seal and do it regularly. Trailer brakes add to the problem big time. I bought a near new trailer and had to bring it home, an 8hr drive, my nephew who is a mechanic happened to ring me as I was starting out, he said pull over in 30 minutes and put your hand on the hub then do it every hour after that. I said but its new, he said just do it half them don't get enough grease when being assembled.

[Morville]

I agree, was told once by an older mechanic to never dunk the hubs in the water when hot. The air in the hub has expanded with heat and when it cools suddenly it can only do one thing while under water when suddenly cooling, suck in water and if it's salt water even worse. Grease and water don't work to well together. When I trailed a boat I checked the hubs 6 monthly. No axle seal no matter how good can stop this happening. You must stop and let things cool down or get caps with grease nipples on and pump in marine grease till it comes out the seal and do it regularly. Trailer brakes add to the problem big time. I bought a near new trailer and had to bring it home, an 8hr drive, my nephew who is a mechanic happened to ring me as I was starting out, he said pull over in 30 minutes and put your hand on the hub then do it every hour after that. I said but its new, he said just do it half them don't get enough grease when being assembled.

I don't subscribe to pumping the hub full of grease until it comes out around the seal. Firstly with a regular trailer seal the lip faces inward so any positive pressure within the hub will make it seal better. The grease will only push out the seal or the grease cap. Secondly with the hub full of grease there is less room for any air expansion when the hub heats and again the inner seal or the grease cap will push off.
Peter

[Just Cruzin]

I don't subscribe to pumping the hub full of grease until it comes out around the seal. Firstly with a regular trailer seal the lip faces inward so any positive pressure within the hub will make it seal better. The grease will only push out the seal or the grease cap. Secondly with the hub full of grease there is less room for any air expansion when the hub heats and again the inner seal or the grease cap will push off.
Peter

Bearing buddies have pressure relief holes in the front of the hub.

[Trisome]

there is a different in grease that doesn't seem to be talked about here.
From memory its called dropping point and it has to do with the temperature the grease melts
or forms into drops. again from memory the best is around 190 degrees, where most grease
specs are much lower. might be a question you might like to ask of your grease supply point.
I found it is something you don't find at your superstore type outlets, the higher quality grease takes
the pressure of poor quality bearings. If you have better quality bearings as well there will be
no problem. suit yourself.

trisome

[Pajshomoneroguntero]

Thanks for all the feedback. OJ it's interesting you mention too loose. I wouldn't have thought I had it too loose. In fact it's reassuring that the technique I used is no different to what has been suggested. I take on board OJ's advice to potentially tighten rather than back off to the nearest pin hole. In my case I am reasonably sure I backed off to only experience a minute amount of float and then really only because I knew to look for it and it was in contrast to the pre-loaded state tightening to the next nearest pin hole. With the wheel on I don't recall noting any significant play maybe a millimetre at the tyre circumference.

Perhaps the bearings were destined to be stuffed in short order following Richard Cranium's pin punch installation of the race.

[geopaj]

It definitely could be a damaged bearing cup.

Is it consistently the same wheel/hub that your having trouble with?

If yes, given everything else appears to be ok, thinking outside the box, could there be an issue with the wheel or tire (ie badly out of balance which is putting extra forces into the bearing? - I always insist that my trailers run wheels/tires that have been balanced).

[old Jack]

It definitely could be a damaged bearing cup.

Is it consistently the same wheel/hub that your having trouble with?

If yes, given everything else appears to be ok, thinking outside the box, could there be an issue with the wheel or tire (ie badly out of balance which is putting extra forces into the bearing? - I always insist that my trailers run wheels/tires that have been balanced).

All good thoughts. Is the tyre out of round or the rim bent? Is the tyre wearing evenly?

OJ.

[Pajshomoneroguntero]

The wheel was on the other side (blue grease) for the run down from Cairns. The inside shoulder tread has been significantly worn obviously just prior to the bearing failure. I've rotated this wheel/tyre to the side it is on now(red grease). So very possible that it is in need of a balance. Could very well be stuffed too adding to the already $1600 for the $20 bearing fail
I'll endeavour to get a pic of the tread up soon.

[old Jack]

The trailer could also have a bent stub axle, this would show as uneven tyre wear and also load up the wheel bearings.

OJ.

[Geoff]

....A youtube vid of how to install theses seals implies that the seal is pressed against the axle flange or similar to hold the seal in place......

I've used marine seals for a few years now, and have found that whether the rubber component would bear against a shoulder or not depended on the axle. Some did, some didn't. Where they didn't, I used an old std seal or an appropriately sized o-ring to fill the gap behind the seal. Anything to ensure that the rubber part of the seal remained where it should. If marine seals were available, I would use them in preference over any other style.

FWIW, I don't use high temp grease. It's not recommended for trailers as the hubs don't get hot enough to warrant it

My 2c....

[Pajshomoneroguntero]

I've used marine seals for a few years now, and have found that whether the rubber component would bear against a shoulder or not depended on the axle. Some did, some didn't. Where they didn't, I used an old std seal or an appropriately sized o-ring to fill the gap behind the seal. Anything to ensure that the rubber part of the seal remained where it should. If marine seals were available, I would use them in preference over any other style.

FWIW, I don't use high temp grease. It's not recommended for trailers as the hubs don't get hot enough to warrant it

My 2c....

Thanks Geoff

[Pajshomoneroguntero]

Pic of the tyre. This is now on the red grease side rotated from the failed side (blue grease side). The wear was associated with the initial bearing failure.