The options are “overslung”, where the spring is mounted over the axle, or “underslung” where the spring is mounted under the axle. ... The difference in deck height between an overslung and underslung setup using straight beam axles is normally the depth of the axle and spring packer plus the full thickness of the spring.

Is underslung axle legal?

It is now illegal to build car trailers or any other trailer without spring suspension in NSW.

What is underslung axle?

Axles with springs mounted below the axle are referred to as underslung, and axles with the springs above are overslung. The difference between overslung and underslung (other than the spring position) is the location of the spring seat, as well as the orientation of the U-Bolt and other hardware.