DIY: Easy rider
Finding the ideal caravan suspension and brake setup.
Finding the ideal caravan suspension and brake setup
Despite there being much more advanced suspension systems, many caravans are still equipped with beam axles, leaf springs and electric drum brakes. This setup is simple and durable, and is well-suited to heavy-duty applications, but there are other ways of doing it.
If you already have the typical caravan setup and simply want better body ground clearance and approach and departure angle clearances, then an axle flip-over conversion will suffice.
The most important thing about this modification is to not do the work yourself if you are not the technical type. Give it to a qualified mechanic who is familiar with caravans and you will also avoid safety and legal consequences down the track.
Most caravan beam axles have under-slung leaf springs – meaning the springs are bolted on with U bolts and attach underneath the beam axle.
Some like the idea of taking off the axle and fitting it under the springs; yes, you’ll increase ground clearance but this is not recommended, as you open up the risk of the axle coming loose on its U bolts and disappearing down the road. What’s more, the underbody clearance won’t change as the beam axle is the same distance from the ground, so you’ll still have clearance problems on high-crown dirt tracks.
The only option – with a typical caravan axle, at least – is to flip the axle over to gain more clearance. You’ll still have the safety net of the axle being contained within the leaf springs, and you’ll also gain more ground clearance than an underspring conversion, as the wheel stubs will sit below the axle rather than above it.
While the axle flip job adds a relatively modest increase in van body height (depending on the axle, about 50mm), watch for unintended consequences including handbrake cables and brake electrical
connections that are too short (these may require replacement). An annexe that no longer reaches the ground and a drop step that leaves too much of a gap to the ground are also potential problem areas.
To see if your van will have these problems, it helps to jack it up first to the expected height increase and see how it measures up.
There is also the matter of van stability – as you are increasing the centre of gravity you could be making it less stable than it was.
Another type of beam suspension is the torsion beam type. While quite simple and compact, these are generally only seen on some lighter vans as they don’t tend to be as good as leaf springs for heavy hauling.
Simple, plain beam axles and leaf springs, when correctly set, do a great job of load sharing, absorbing road shocks – on smoother roads, at least – and generally prove the most cost-effective and durable caravan suspension setup. If you’re unlucky enough to break a leaf spring, they can be relatively easily repaired to limp home or replaced with a new one. It’s for these reasons that they’ve proven so popular.
But if you’ve found yourself tempted to venture down more high-crown dirt roads, or even if you’re just heading along paved roads that are rough enough to throw your van and its contents around, it might be time to look at independent suspension.
Of course, modifying your own beam-axle van with independent suspension is expensive and would require engineering certification so, instead, it is more a consideration for when you are buying your next van.
The independent suspension generally carries less unsprung weight than a beam axle, so it absorbs bumps more quickly and smoothly, and it does
not rely on the springs to locate the axle, reducing the chance of bump steer, that is, transferring some of the shock loading on the opposite wheel causing it to move. These advantages all permit the independent suspension to provide a better ride.
There are a couple of independent suspension arm designs and four different types of spring that can be used.
Independent suspension has typically either a trailing arm design, or an A-arm design. These suspension arms use torsion bar springs, coil springs or leaf springs.
If you wanted the supplest, money’s-no-object suspension setup for your caravan, air springs and A-arms are the way to go. However, load sharing of the van’s weight is not as good as a linked independent (or beam-axle – roller-rocker type leaf spring) setup for tandems.
That’s the theory but, like so many of these choices, it comes down to the design integrity of the setup. If it’s poorly designed and installed, it’s not going to improve on a basic but well-engineered leaf spring beam axle setup.
Many vans have basic, electrically-activated magnet drum brakes. These brakes, like the beam axle and leaf springs, are relatively simple but some people find they’re not the most effective or satisfying brake system to use. They’re not always trouble-free either, but that’s most commonly due to poor maintenance or abuse.
Electro-hydraulic disc brakes give a better brake ‘feel’, better retardation and fade-resistance than drums but, like the independent
suspension, you’re paying a lot more for the privilege.
The override (inertia) hydraulic brake system can be used for trailers up to 2000kg, beyond which the legal requirement for breakaway brakes obviates the ability to use this design. But it’s not perfect, as you don’t have any control over the trailer brakes from the driver’s seat (other than slowing the towing vehicle, obviously) and the trailer brakes’ activation is delayed by the time required for inertia to act on the hydraulic ram on the coupling. This leads to a rather jerky braking action.
The law doesn’t stop you using override brakes on a trailer heavier than 2000kg Tare, as such, it’s just that it is a legal requirement that the driver has the ability to control the caravan brakes independently from the driver’s seat and also for the caravan to have a breakaway system – and there aren’t any means of doing these things with the simple override system.
The next option up the ladder are electrohydraulic brakes, which use electric activation of a hydraulic system, meaning you get the instant response when braking and the stopping power of disc brakes. This system is controlled at the vehicle with an electric brake controller, and can have a breakaway system installed just like a van with electric brakes. This system is not cheap either, but if you want the best, you have to be prepared to pay for it.
Top left: A conventional leaf spring over- slung beam axle suspension setup. Above: flipping an axle can be done but it shouldn’t be underslung.
Clockwise from top left: Torsion spring beam axles are quite rare on caravans; independent trailing arm suspension with coil springs and dampers is the ultimate setup; override brakes are the default basic braking system but are not seen much these days; electric drum brakes are the standard caravan brake setup; beam axles with coil springs gives a good ride quality but isn’t common anymore.