Thread: Suspension Upgrade

Axle depending on what's there.

And brakes? Isn't 750kg the max gross weight for unbraked?

Sorry yes brakes are a given - was thinking more along the the lines of spring hangers and tow hitch - are there differences in these between 750 and 1000?

I note in the regs that it says for self assessment of a 750 Kg trailer the components must be rated at 750 or more. That seems to imply you can over engineer and still call it 750. (& safely carry up to a ton without straining anything)

I've not seen caveats about hitches.

Can't help with your other questions sorry.

Originally Posted by Wombat2

Apart from the springs what else would be needed to upgrade the rating of an existing trailer from 750Kg to 1000Kg?

On a single axle trailer, the axle bearing sizes are the thing that determines a trailer's carrying capacity, with springs coming a distant second. With the exception of some lightweight pressed metal couplings, couplings are rated starting a 2000Kg. The same spring fittings are used in kits up to 1500Kg per axle (3000Kg tandem).

Is the trailer currently registered?

I had a customer bring his trailer in to do an axle upgrade and retro-fit brakes. When all was finished, I rang Vicroads to enquire about changing the registration information to reflect the new carrying capacity, and their response was that they would require an engineer's report to determine that the trailer would be capable of handling the extra capacity. With an engineer's report costing more than the trailer's replacement value, we de-registered the trailer, gave it a new VIN number, and re-registered the trailer with its new carrying capacity.

I will add, that it was in my professional opinion that the existing trailer would handle the extra capacity, and in giving the trailer a new VIN number meant that my name was on record as being the manufacturer the trailer, and giving it that higher rating.

Thanks for the tip on registration - yes it is currently registered.
This is the trailer - 7X5



I want to fit electric brakes and figure at the same time I may as well take it up a notch or two. Without the cage and each end down it will just take an 800Kg Morris Mini if I need to on the rare occasion. I also have a bit of landscaping to do so lots of rock, dirt and soil to cart so it will get heavy quickly.

Looks a nice trailer David. Might be worth a phone call to QLD D.O.T. and find out what hoops they want you jump through to up the rated capacity.

Alternatively, you could just put the heavier axle and brakes on the trailer, and leave the 750Kg rating, but giving you peace of mind knowing that you can safely carry more than that.

While you're changing the axle anyway, have a look at what the extra cost is to upgrade to "Slimline" (Falcon bearings). It will give an axle capacity of 1450Kg, and even if you dont think you need that, the odd occasion you put an 800Kg car on a 300Kg trailer, you'll be pushing the friendship of a 1000Kg axle.

Thanks Yonnee- I've been looking at complete kits that supply double hole springs as opposed to the slipper springs I have fitted now. It would be easier to stay with slipper but if I change do I have to move the front hangers?

For the same size spring (width, thickness & quantity of leaves), Slipper springs are generally slightly firmer, have a slightly higher capacity, and will sit the trailer an inch lower than Shackle springs. Without the rear shackles, Slipper springs are virtually maintenance free.
If you do change, and you dont change your front hanger, you can expect the axle to be further rearward 1-2", however this can vary depending on whose springs are currently fitted, and whose springs you replace them with.

Looks like I have more to do than a spring upgrade. I bought this trailer off eBay sight unseen but checked out the manufacturer - Dunbier - big name in marine trailers and also make box trailers so I thought OK should be a quality build. I was working in Brisbane last week so my wife picked it up and I didn't see it properly until today. - bit disappointed with the build.

It's basically a bolt together job - 4 bolts hold the draw bar onto the body of the trailer and then it doesn't even touch the chassis frame.

You can see the floor (2mm) is pop riveted to the frame and screwed up the middle. The mudguards are screwed on. Draw bar is 60x40 RHS and the chassis frame is 40x20 RHS

The "removable" cage won't be a quick and easy job - 4 nuts and bolts down each side with a pile of washers on each to separate it from the body.

At least it's galvanized

Hj
looks like a china import...
the one big green shed sells...????
Tony

Originally Posted by antoni

Hj
looks like a china import...
the one big green shed sells...????
Tony

Plate says manufactured by Dunbier Braeside Melbourne

(It's basically a bolt together job - 4 bolts hold the draw bar onto the body of the trailer and then it doesn't even touch the chassis frame.

You can see the floor (2mm) is pop riveted to the frame and screwed up the middle. The mudguards are screwed on. Draw bar is 60x40 RHS and the chassis frame is 40x20 RHS)


Having spent 40 years in the steel fabrication game, in my honest opinion going by what you have said here, I would NOT do an upgrade as it would have been designed to JUST make the 750KG rating. The suspension (1000kg) would be to stiff and the trailer would shake itself to pieces as the whole thing is to light. If you know an engineer get them to take a look at it or ask Dunbier for an engineers report on the trailer.
Regards
Kryn

Right there Kryn - won't be rushing into upgrading - more like beefing up the existing structure to cope with its rated capacity.

OK - forget the suspension upgrade for now I've got to be sure this trailer will at least cope with it's original load rating and more.

As the drawbar is only bolted on it will be easy to get off and replace so I'm going for 75x50x3 RHS - tie it back to the front hangers and make it a little longer - 1500 as opposed to the just under 1200 it is now. (any point in going longer than 1500?)

Would a cross piece of 75x50 RHS inline with the front edge of the chassis be of benefit? or should I put it further forward and use it as a spare tyre support?

As for the chassis I'm open to suggestions without totally rebuilding it - currently it is 40x20x? I'm thinking of running a 'ladder' of 50x50x4 angle up the middle third - would that help spread the load?