From the front of the trailer, mark 1875mm for the centre of the oscillator/rocker unit. This suspension offset is 75mm back from centre and unless you are fitting heavy rear hinging ramps or have a typical load which will add excessive weight to the rear of the trailer, this offset will suit most applications.
Set up your suspension rocker so the main rocker bolt centre is lined up with the suspension offset you have marked and clamp in position. Set up the front spring in its hanger and fit to the rocker unit.
Adjust the spring so that the tail of the spring can move freely when the rocker oscillates without binding or dropping out.
Make sure that the outside spring edges are flush with the outside edge of the chassis rail and once double checked, tack weld the spring hanger and suspension rocker to the chassis rail.
Once this is completed on both sides, position the slippers over the spring tails allowing for clearance between the spring and the slipper for the spring to move in and out when loaded.
Again make sure the outside edge of the spring is flush with the outside edge of the chassis and tack weld the slipper in place.
Once all components are in position, remove the springs and fully weld around the hanger, rocker, slipper and packers.
Now is a good time to measure up your axles - Click here for details on "Axle measuring".