Why caravans should have a wheel at each corner

Have you ever wondered why caravans have their wheels clustered around their middle? I have.

Most trucks and cars don’t and unlike them, the basic configuration of caravans has many dynamic disadvantages.  

Having a large, slab-sided body overhang its fulcrum makes a conventional caravan inherently unstable and much more susceptible to side winds and buffeting from passing trucks.  

Trying to pivot the van around its centre point means that you are working against, rather than with, its tyres, scrubbing them sideways and generating friction each time you turn.  

Because of this overhang, your caravan also has to be higher at the front and rear to avoid contact with the road surface, such as when entering service stations in tropical Australia, or steep driveways at home. Raising its centre of gravity also adds to instability.

Because the chassis has to support so much unsprung weight, heavier gauge steel has to be used to support the overhanging superstructure.   

On off-road caravans, you need a more heavily-raked rear end to ensure body clearance in undulating country, or when crossing creek beds.  

Layout restrictions

Inside, clustering the wheels in the van’s midriff poses layout restrictions.  

Unless you raise the caravan’s floor above them (further raising its centre of gravity), the wheel-boxes intrude heavily into interior space. This has resulted in what is considered a typical Australian layout, with the lounge and kitchen amidships, spanning the wheel-arches.  

The problem is even worse in off-road caravans, like the one I owned, as a raked rear-end further limits layout options. In our case, a transverse queen bed disguises the upswept rear floor.  

And what about towing stability? We are forever being lectured on correct ball weights, the need or otherwise for weight distribution hitches, sensible distribution of weight and the effect of all these on the tow vehicle’s payload.

Thinking outside the box  

So, let’s let’s slip our minds into neutral and think differently – ‘outside the box’, if you like.  

What about a caravan with a wheel at each corner, not unlike those portable ‘homes’ that grader drivers and road construction crews tow around with them? Or even the truckies’ favourite – the ‘dog’ trailers   

A wheel at each rear corner would eliminate the issue of ‘overhang’, on or off-road, while the front wheels could turn using a centrally-pivoting A-frame. Or, while we’re at it, perhaps dispense with all that complexity and mount a single wheel at the front.  

Like most things in this world, these ideas are not new and if you check out popular caravanning forums you’ll see a lively exchange and discussion about these concepts.

However, with caravans getting larger and heavier as we attempt to replicate our comfortable homes in remote areas, perhaps it’s a good time to re-ignite the discussion.

The upside for cornering

The advantages of moving the wheels to the corners of a caravan are many…

For a start, with appropriate suspension, you increase stability and resistance to side winds and buffeting. As the rear is doing little work, you could save further space and cost by using a simple leaf-sprung solid axle.

And as these wheels don’t need to turn, you could have them covered largely by removable ‘spats’ like those fitted to the Series I Jaguar 2.4 models of the late 1950s.   

The front wheels could utilise car-like independent suspension, camber and castor to ensure they deal with bumps, and allow the van to follow the tow car faithfully. If you have two wheels at the front, you would probably connect them via a pivoting A-frame-like set up; if you opt for a single wheel, things would be even simpler.   

Three wheels even better  

Personally, I favour the idea of a three-wheeler caravan, with a single wheel steering the front, but using large diameter wheels all-round to minimise disturbance from the road surface. Maybe even torsion bars that would allow the suspension to be wound up or down, depending on the roads you planned to travel on.  

Either way, the caravan would be easier to turn, as the front wheels would point in the required direction and the rear wheels, being so far back, would be subject to less side-loading than a conventional tandem-axle caravan.  

Another big advantage of a self-standing caravan with wheels at its extremities is that it would have a very small ball or coupling down-load. Without having to worry about eating into your payload, this potentially could open the way for smaller vehicles to tow larger caravans.  

Storage between trips would also be much easier. The A-frame could be folded back against the body when not in use and even locked in this position for secure storage. A pop-top family caravan with this feature could potentially fit in a normal garage.

More interior options

Inside, the ‘wheel-at-each-corner’ concept opens up a range of new layout opportunities.  

One of the problems with today’s caravans, is that the market’s demand for a separate shower, toilet, vanity and laundry has led to caravans becoming longer, with all these features usually accommodated in an across-the-body bathroom.   

This in turn has placed more weight rear of the axles, while fitting the rear entry door favoured by most buyers pushes the axles further forward on the chassis, reducing ball load and potentially affecting stability.   With this new caravan layout, the weight of the bathroom could be concentrated more safely within the caravan’s wheelbase.

Beauty or safety?  

Of course, I hear the chorus of nay-sayers telling me that this sort of caravan would be ugly. Do you seriously think that our current caravans are beautiful?  

When visualising the sort of vehicle I’m talking about, post people think of those road construction vans I mentioned earlier. But who said this type of caravan has to be a box?   

Some years ago, I reviewed the Echuca-built prototype Aerovan that effectively added a domed fibreglass roof and curved front and rear fibreglass modules to what was essentially a rectangular composite-walled box. Some people said that it resembled a double-ended horse float, but I thought it looked pretty smart. Anyway, you’ve got the idea.   

So, let’s start re-thinking the caravan. There are arguments against the wheel-at-each-corner concept, but most are based on market acceptance rather than dynamic issues that smart minds could overcome.  

What do the experts think?

We spoke to some industry experts and truckies; many of which encourage a closer look at the radical wheel-at-each corner caravan concept, as a way to reduce caravan accidents and improve road safety.

Suspension expert Deon Van Deventer, told Caravancampingsales that the ‘wheel-at-each-corner’ caravan concept was both feasible and overdue.

“There’s no doubt in my mind that a well-designed and manufactured dog trailer/caravan will leave its traditionally styled compatriots for dead,” he said, citing superior stability and control as major reasons.

“The design itself is inherently more stable with the load being supported in four corners – no coincidence that motor vehicles, freight trailers and road trains all resemble this layout.

“It is much less sensitive to imbalances in load distribution within the van, an issue that is the primary cause of many caravan handling problems, ending all too often with disastrous consequences.”

Van Deventer said anti-sway systems provided vital back-up, but they could not cure a poorly-designed van nor prevent sway from starting.

“All it will take to get something going is a bit of collaboration between a components supplier and a caravan/trailer manufacturer,” he said.

Truckie and road safety advocate Rod Hannifey is another fan of the concept, and even supplied some real-life photos of a New Zealand-based caravan from a few years ago built with dolly front wheels.

“There are no doubt obvious benefits from the concept you propose, but I think the biggest issue would be getting the right weight distribution and handling,” Hannifey said.

“Backing of dog trailers would be beyond many as few can back a van now it seems and whilst some dogs have lock pins, this helps when empty and may work with vans, but they can take years to master and so for the odd tripper, perhaps too hard.”

RV safety expert Colin Young, who at one time was involved in a trailer project in the USA involving both pig and dog trailers, said handling and stability could be far superior with dog (wheel at each corner) trailers, but the critical issue was the body twisting on anything but smooth and level roads.

“The main disadvantage, safety-wide, of both dog and pig (wheels at the centre, e.g. conventional caravan) trailers, compared with 5th-wheelers, is the fact that the articulation point is mounted quite some distance behind the rear axle of the tow vehicle, so that when you turn one way, the front of the 'van has to travel the other way,” he explained.

Tony Thomas, of Caravan Relocation services, was also enthusiastic about the concept, believing any manufacturer that “embraces the wheel-at-each-corner’ idea with lots of research and development and comes up with a great looking caravan will be on a winner”.

Thomas said that over the past decade he had noticed how the axles of many single or tandem-axle vans had been pushed back even further, increasing ball weight substantially.

“With these new utes that are legal towing 3.5 tonnes, yet weigh little more than two tonnes, it has become a case of  ‘the tail wagging the dog’ and this in my opinion, along with driver inexperience, causes many caravan crashes.”

Ex-truck driver Terry Seymour agreed with many others that reversing would pose a major problem with the wheel-at-each-corner design.

“I drove trucks for 50 years including road trains for the last six years and with dogs it was a whole new world learning to reverse,” Seymour said.

“If you think the caravan public have problems now, introduce a dog combination and half their holiday will be taken reversing!”

But not everyone agreed.

“Brilliant idea; backing up no problem,” commented caravancampingsales reader Colin Royston. “Do what good truckies do; uncouple and connect to the front of towing car and push it anywhere you want – just have to buy another tow ball.”

Another reader Andrew Morom put forward a simpler solution.

“For those that think it is impossible to back with a double pivot, just do what the trucking industry has done – fit an electric pivot lock on the turntable and then it only has the one pivot point at the tow hitch,” he said.