Thread: Slipper to shackle springs

I explored the same issue a couple of years ago. I got rid of the short 5 leaf slipper springs and fitted Alko 4 leaf shackle springs + small shock absorbers and then removed the bottom short spring leaf so that it is now 3 springs. It carries about 750 kg -900kg all loaded. It rides the bumps and corrugations very well (Cape York Peninsular Development road) (lack of broken glass/crockery) ... there seems to be a lot of misinformation about 'offroad' trailer suspensions... they just shake themselves to bits when they're too hard...

Yeah, its the shake itself to bits thing i want to address before i have any problems.

Rick
you can go with some trailer companies idea of a spring???

On leafer trailers I have used:
-falcon wagon rear leaves
-hilux front leaves
-78 series rear leaves

If you can package them into your trailer the 78 series leaves with the two load leaves and then two intermediates removed: a pair of dampers will ride as smoothly as coil suspension

I would go falcon rears over hilux fronts if I couldnt package 78 series rears

Factory springs are generally very very good material to the point on factory leaves I never recommend or carry spare leaves - if the trailer is running ALKO or other trailer maker junk a spare leaf pack is very very good insurance!

Using factory springs is usually cheaper if you have the fabrication skills - all the above leaf options can usually be had for next to nothing - New shackles/ dampers and some fab work and you will have the trailer riding smooth in a weekend!

S

The falcon springs look like a good place to start. Long, common and cheap. Will have to get under there with a tape measure and see what lenghts i can fit.

Yes i can fab new mountings. While i have used factory trailer leaves and hardware before, i dread using the cheap junk again.

With the leaf packs you have used, did you set the shackle angle up as per a normal (car) setup or the odd angle they recomend for trailer packs?

my theory is vehicle makers have spent mega bucks making leaf spring rears both carry a load AND ride smoothly

this is why they dont use dicky 600mm long springs like trailer manufacturers - whose engineering expertise I think extends as far as "lets just make it cheap"

Set back the shackle for ~45 degrees at ride load and height
Gives maximum travel and smoothest ride

When using soft long leaves dampers become almost as important as a coil sprung design - try to get proper dampers as vertical as possible

S

Ok, just went for a crawl under it with a tape measure. Without moving the drawbar, an overly long spring will be out of the question. I could proberly squeeze in a spring with a length of around 480mm from fixed mount to centre bolt.

A sort through of my collection of springs and picked a set of Suzuki Sierra fronts, around 970mm long, military wrap on the shackle end. I have enough leaves to play around with the packs a bit. They are almost flat with little free camber, with mounts and the axle slung under the springs, ride height would change very little by the looks of it. I would have a matching pair of Sierra shocks floating around as well.

Do you think these would be long enough to be worth the effort? To go longer i would have to move the drawbar forward to gain space, which is not such a big drama i guess.

I cant imagine a very good shock arrangement with a spring over axle setup on a trailer.

Cut a hole in the floor pan
build a tower
call it a feature !!!!

S