What is a caravan chassis?
The steel frame everything else bolts to.
It is also the part you cannot change your mind about later.
The steel frame the whole caravan is built on, running the length of the van and carrying the axles, the drawbar and the body. How big the rails are and how the steel is protected against rust are two of the things that separate a van built for bitumen from one built for gravel.
- Job - carries the axles, the drawbar and the whole body
- Varies by - rail size, how it is braced, and how the steel is protected
- Weight - a heavier chassis leaves less payload inside the same ATM
What the chassis is
The chassis is the steel frame a caravan is built on.
Two main rails run the length of the van, cross members tie them together, and the drawbar runs forward from the front of it to the coupling.
The axles, the suspension and the body all mount to that frame.
Rust protection is the difference you cannot see later
Steel gets protected in one of two broad ways.
Hot-dip galvanising lowers the finished frame into molten zinc, so the coating reaches the inside of the rails as well as the outside.
Paint and powder coat cover the outside only.
The difference shows up where water and grit collect and stay: inside the rails, at welds, and around any hole drilled after the coating went on.
Coastal air and long stretches of wet dirt road are where it is tested hardest.
Heavier is not automatically better
A deeper, thicker chassis carries more and tolerates corrugations better.
It also weighs more, and that weight sits inside the van's ATM.
Every kilogram of frame is a kilogram you cannot pack.
Two vans with the same ATM can hand you very different payloads for that reason, so it is worth reading the chassis and the payload figure together rather than one at a time.
What to look at on an inspection
- Welds - flaking and surface rust at welds and at drilled holes
- Rails - straightness, and any sign the underside has been struck
- Drawbar - rust where the stone guard and gas bottles bolt through
- Coating - whether the protection went on as a dip or as a surface coat