Thread: Campertrailer suspension mods

Spring under axle is standard, however spring over axle is legal and is normally used on high ground clearance trailers. There is absolutely nothing in VSB1 that comments about spring over or spring under. I have manufactured trailers with SOA and none have been faulted at registration.

Something worth thinking about, is the chassis strength in relation to single point loading as per air springs in comparison to 2 point loading as per leaf springs. This puts more stress into the chassis, so needs a stronger chassis. You will have to be there judge as to whether you have a strong or "enough" chassis.

Converting from slipper springs to shackles is a great idea for offroad. Slippers, especially when setup as SOA can take enough force for it to rebound and fire the slipper out of its mount - even with the spring poking through by 50mm which is how we set them up. The rebound is only controlled by the main leaf, not the whole leaf pack in many cases for light springs. You can get springs with a bend in the end of the main spring to prevent this, however I think that will hammer the mount and eventually rip the mount out.

Shocks for offroad are a great idea. I remember Vic Widman saying 20 years ago, it doesn't matter what suspension you have for offroad, it needs to have shocks.

I would also say, if you're running 4wd tyres, go straight to a 45mm axle and Ford type (ie 1350-1500kg) rated bearings so it doesn't fail.


What would I do

I would just run soft shackle springs, they tend to be very stiff from the factory, the above axle/hub setup and run very soft tyre pressures to suit the load - these absorb shock.

Originally Posted by Slunnie

Spring under axle is standard, however spring over axle is legal and is normally used on high ground clearance trailers. There is absolutely nothing in VSB1 that comments about spring over or spring under. I have manufactured trailers with SOA and none have been faulted at registration.

Something worth thinking about, is the chassis strength in relation to single point loading as per air springs in comparison to 2 point loading as per leaf springs. This puts more stress into the chassis, so needs a stronger chassis. You will have to be there judge as to whether you have a strong or "enough" chassis.

Converting from slipper springs to shackles is a great idea for offroad. Slippers, especially when setup as SOA can take enough force for it to rebound and fire the slipper out of its mount - even with the spring poking through by 50mm which is how we set them up. The rebound is only controlled by the main leaf, not the whole leaf pack in many cases for light springs. You can get springs with a bend in the end of the main spring to prevent this, however I think that will hammer the mount and eventually rip the mount out.

Shocks for offroad are a great idea. I remember Vic Widman saying 20 years ago, it doesn't matter what suspension you have for offroad, it needs to have shocks.

I would also say, if you're running 4wd tyres, go straight to a 45mm axle and Ford type (ie 1350-1500kg) rated bearings so it doesn't fail.


What would I do

I would just run soft shackle springs, they tend to be very stiff from the factory, the above axle/hub setup and run very soft tyre pressures to suit the load - these absorb shock.

Many thanks Slunnie, all excellent advice.

I don't think you can beat a good leaf spring set-up for simplicity in a trailer. The springs in our camper trailer are nice and supple and give a good ride over rough terrain. As Slunnie says, most trailer set-ups are way too stiff for the weight they carry.

I have been pondering building a flat tray style trailer to carry my new slide on camper. As most std trailer springs are very short and stiff, I had been pondering using something like rear landy springs, which are much longer and I can play with the leaf counts to get the ride I want? There is usually plenty of room under a trailer for a long leaf set-up.

Off topic, but I've read that the rules for trailer engineering have changed in the last few years? It is now no longer able to get a new build engineered without very specific physical load testing of the drawbar? That this testing requirement has effectively killed the ability to home build a one off trailer?

Chris