blown4by replied:

I can't see why it would be illegal if carried out in a professional manner as underslung or overslung are just optional ways of mounting the suspension. You will need to check if the axle is cambered, if not you can just rotate it 180 degrees to get the spring centre bolt locating packer plates on top of the axle. If it is cambered you will need to grind the welds off the packers and mount them on top of the axle and re-tack them in place once the 'U' bolts are tight and you have centralised the axle to the width of the trailer. When you re-tack them you only need about a 6mm tack at the front and rear of the packers. Do not weld them at the sides because this is like welding "across" the axle which is not a good idea. They must be tacked in place because it is they that prevent the axle moving sideways when the spring centre bolt head is located in the hole provided in the packer and the 'U' bolts clamp the whole assembly together. You will be raising the centroid of the trailer slightly by doing this.

Dirty Dan replied:

Thanks for all the great info. Have heard of people doing this mod but wasn't sure if it was only legal to hang axle this way because it was manufactured like it from factory etc..... But I think your right, if it can be made hung either way to start with I can't see why It couldn't be changed around with no consequence.

96 GXL 80 series replied:

Dan,
it is better to have it set up that way as it takes the actual carrying weight off the "U" Bolts as the spring is sitting on top of the axel.

Most trailers are made with the under slung spring to cater for the average car or station wagon as a tow vehicle.

Happy New Year
96

rumpig replied:

i've done it to my caravan and gained 5" of lift, as far as i know i don't need to get it engineered. just make sure you get new u bolts when you do it, they are cheap as to purchase from a trailer shop and make sure you retighten them after a short drive

furph replied:

DD.
There can be pitfalls in this exersize:
Where the axle is over the spring the clamping plate is pulled up snug to the curvature of the spring by the U bolts.
When the axle is below, the clamping plate is tending to only bear against the top spring leaf at its ends, leaving a gap in the centre of the spring. Flexing of the spring pack as the axle pushes up can cause U bolt loosening and for the spring to break across the centrebolt line.
If you draw a single line sketch of the 2 setups you will see the difference.
The solution (as done on vehicles built with spring over) is to have clamp plates over and under the spring, machined with curves to match the springs.
furph