Rust inside??

[cjj216]

I have a single axle braked trailer with an Alko 1300kg axle, “waterproof” bearings etc.
I’ve had it from new and it’s coming up to 10 years old.
Launched and retrieved only 2 or 3 times a year.
Properly maintained.
Box sections flushed through thoroughly after every retrieve so all good with no rust anywhere.
Thing is, the only parts that aren’t galvanised are the suspension units - the black hollow tear drop shaped things you can see in the pic.
The black turned to rust within a year of ownership so each year I wire brush these units at the end of each season and paint them in that galv paint stuff.
I’m thinking that water must get inside these units when launched thus rotting them from inside out?
No way of knowing what’s going on inside these units so is it time to replace axle?
If I do, can these units be drilled and waxoyled inside?
It does 4x 300mile tows a year so safety is paramount.
However, don’t want to waste £500 if not needed.
As I say, on normal inspection, trailer is in top condition.

[simonl]

Are you sure the arms are hollow? I believe mine are cast, and solid.
A hammer should give you an idea of their integrity.

[spartacus]

Pretty sure they are solid cast iron.

[cjj216]

I have a smaller indespension trailer on another boat. That has solid cast units.
The al ko ones are Definitely hollow they are pressed metal in two halves and either crimped or seam welded together. Each year now the top layer of paint flakes off with rust.
I do give them a tap with hammer but I think it would fail on the road before the metal was that thin that a hammer would go through with a gentle tap.
I suppose the answer is to replace and then cut my old ones in half and see what’s gone on inside.
Expensive exercise though if all was fine!!
Would be interested if any owners of older
alko axles have experience failure of this part?
I’ve emailed alko to see what they say as the construction is still the same on new ones.

[Orwell boy]

Yes there definitely hollow ,however are you sure their 1300kg ,the last new axle i bought from al ko was 1000kg and had those hollow supports ,but i thought the 1300kg was different arm solid , anyway my trailer man said some do fill with waxoyl ,but i reckon breaking the galv by drilling will have a more negative effect , if their dry inside then dont see their going to be too much bother ,i reckon they are doing well at 10 years ,more than i thought when i saw them delivered to me ,i reckon they must be well sealed or they would have rusted through by now ,al ko axles do ride so much better than others though worth alot to avoid damage to your boat

[jeffstevens763@g]

On mine which were hollow I heated up denso petrolartum paste filled inside through the drain hole and coated inside it sets when cold just open the hole back up for drainage.

[cjj216]

Orwell boy - just checked. Mine’s actually a 1500kg axle! See pic.
Totally agree on the ride quality of the axle.
Also, when I bought the boat it was on this trailer and I didn’t like the idea of the “waterproof” bearings.
However, they’re easy to change with a press.
I have a set of drums with good bearings in that I put on for long distance towing (never been in water). 5 min per side to swap when I arrive at destination.
The drums I launch with have had the same bearings in for 5 years and spin up no problem. I reckon they’d be fine to tow long distance. Maybe they are waterproof!?
Not sure how? But my other trailer bearings wouldn’t last a season if they weren’t stripped and greased each year.
Back on topic.... only issue I have with the hollow units is there’s no way of knowing what’s happening inside. I’m just thinking they’re surely not water tight??....but then I thought that about the bearings!!🤦