Have you ever felt how hot your hubs are when you stop at the ramp??

Would be interested in knowing the issue u had to go to oil filled hubs....which are pressure sealed.
Bearing failures
1/ chinese bearings where they have a higher lead content in the steel alloys for cheaper tooling in manufacture
2/ chinese bearings with poor width measurement tolerance so when torque up the std spacer will have the bearing either fractionally loose or fractionally tight
3/ over tighten or too loose on install
4/ Transportation over long distance by rail... or badly balanced or flat spots on a tyre
5/ contamination..spot of grit or moisture either during install or thru seals
6/ incorrect grease or not  correct bearing grease
7/ long periods of sitting with weight on in the one place

Interesting steps you mentioned 4/ transport by rail & 7/ long period sitting - any idea what distance (is south island Invercargill to say Auckland  long enough as that would be common with Stabicraft etc?) and how long sitting in one place ie 4 weeks or 4 months or longer?

The rail issue originally surfaced in the USA shipping on rail from assembly plants to dealers, with bearing rumble on and shortly after delivery to the customer... I also understand from several leyland dealers in NZ in the late 60s and 70s.. early bearing failure was common also shipping from Wellington plants to Auckland by rail.

Sitting... it used to be common practice for caravan and boat owners in the 60s and 70s to chock axles in the off season. Many caravans would be sited at labour week end then brought home for winter at easter or Queens birthday... While on site they also chocked and levelled.... to prevent  tyre flat spots and bearing loading in the same spot.
Radials do not flat spot as such... pumping up to max pressure and running they will re form because of the softer walls... Cross plys will flat spot, when over inflated will feel ok , but when put back to normal running pressure will deform back.
I DO NOT KNOW if modern cross ply construction is still prone to this.

Flat spots... watch how tyres drag on a duel axle when turn a tight cnr....hit the anchors on a braked trailer, or forget to latch the brakes off when revering, espec up a hill.

So checking bearings....check for ANY play in the wheel.. should be NIL.....Spin the tyre, put your hand on the chassis or mud guard and listen / feel for ANY rumble....and feel the tread of the tyre as it spins for any out of round.

Chocking trailers is usually more easy than most think.
Drop the jockey wheel right down....couple axles under the rear of the trailer....now wind he jockey wheel up and the weight comes off the wheels, tyres bearings

"Would be interested in knowing the issue u had to go to oil filled hubs....which are pressure sealed."

My mate Pete has got rid of his oil filled bearing on his trailer in OZ, as they blew out too often on long (500km plus) hauls....not the bearings as such, but the see thru caps you use to monitor the oil.
Swapping out a set of bearings, my word, that was a fun thing to do at 1 a.m. on a servo forecourt at kalbarri two years ago.... :-)

I live out at Huia end of a windy hilly road on side of Manukau Harbour in Akld - not uncommon over summer season to see several trailers with snapped axles or detached wheel etc sitting by side of road with or without dejected owners

AND

Quality grease will not melt under normal use in bearings, even with disc brakes.

I recomn 99% these failures are Not due to being oil filled, or having not having buddies, snapped snapping wheel nuts, whatever... but simply down to lazy, to nil maintenance, expired WoFs and  incorrectly adjusted / installed bearing and elcheapo grease
I ask how many have a pot of quality Brand MARINE BEARING grease and a pot of QUALITY Brand MARINE LUBE grease sitting on their shelf in the workshop?
EG stuff like evinrude triple gaurd bearing  and triple guard lube.. on is red the other blue.
No? got a pot of the pale blue crap stuff they sell at mitre 10/ bunnings/supercheap?
Or have a couple grease guns filled with lube and bearing grease
How many, including your local automotive workshop actually have marine grade grease on the shelf?  OH that adds another $20 on the bill....over std auto grease.
Ask to see the pot of marine grease they have in stock...

Failures, like most failures are the human end of things... not the mechanical
And being human nature, when a failure happens its blamed on the 'tools' anything but the actual reason of failure.

Why can't they make trailer chassis out of C section rather than BOX section? would make it a lot easier to combat rusting.

Fishy11 wrote: fauxpas wrote: Why can't they make trailer chassis out of C section rather than BOX section? would make it a lot easier to combat rusting. Strength difference for starters.... If a trailer is well made, maintained correctly, and washed thoroughly you shoudln't be having rust issues.

Good observation.
I have Walu sitting on her O/E "C" section trailer supplied in Jan '73 and its been maintained correctly. .......ie; nothing particulary special other than regular wash-down, wobble rollers and s/s Duratorque carridge added.

We built tubular speedway chassis using s/s, however found they work hardend and cracked, due to vibration and continual stress......

Walu wrote: We built tubular speedway chassis using s/s, however found they work hardend and cracked, due to vibration and continual stress......

Would you not have thought of that beforehand? Like what would be the pros of running stainless? the chassis is going to be painted anyway.
Not 'hating' but it's pretty common knowledge that stainless isn't going to be as strong (for the same size, wall thickness, weight etc) especially in that scenario as mild steel or chromoly.