Every caravanner knows that uneasy feeling. Often with little or no driver input or warning, you feel the tail of your van begin to wag. Instinctively, you turn the wheel to correct it and, if you are experienced, you won’t overreact. However, if, like many late-onset caravanners, your first towing experience is with an 18-22ft behemoth hanging off your towbar, there is a shallow knowledge pool to draw on and panic reactions can take over.
Enter Dexter Axle, the largest player in the brake and axle business in North America. Fanned by concern that some of its brake business might leach to a market rival, Dexter has created its own stability control – Dexter Sway Control (DSC).
It was launched on the Australian market in August last year and is becoming an increasingly familiar feature, or option, on Australian caravans.
Instead of braking all two, four (or six) wheels together on an errant caravan once sway is determined, the Dexter system applies the brakes on either side of the caravan selectively to bring it under control. In this respect, it is more like the skid and traction control systems used on many of today’s cars.
The degree of braking force applied is also different. Al-Ko’s ESC applies a pre-set maximum force short of lock-up to all brakes simultaneously, with that customised calculation based on the specific caravan’s pre-determined weight, size and even its tyres once unacceptable lateral G-forces are detected. In contrast, DSC can deliver up to 100 per cent of brake force, even up to the point of wheel locking.
ONE SIZE FITS ALL
DSC is a one-size-fits-all system – it counts wheel revolutions and then selectively applies a progressive proportion of whatever brakes the trailer is fitted with and can also be fitted retrospectively to many older caravans. So it is not size or load sensitive, which means it works regardless of how much stuff your caravan is carrying, how well (or badly) you have loaded it and whether your water tanks are full or empty.
Another big difference between the systems is that DSC draws its power from the caravan’s battery and, hence, does not have to be plugged into the tow car for its anti-sway feature to work (although it needs the trailer plug to power its electric brakes in the conventional way), whereas Al-Ko’s ESC draws its power from the tow car for both the brakes and its ESC.
The final feature unique to DSC is that it not only monitors trailer ‘yaw’ – the side-to-side movement, left to right – but also vertical movement. This permits DSC to switch off when offroad conditions are encountered, avoiding ‘nuisance’ braking than can occur if the lateral sensor decides the sideways movement that might occur on corrugations or rough terrain is trailer ‘sway’.
ON THE ROAD WITH DEXTER
So how does DSC work in practice? Very well, it seems, based on our experience in Van Cruiser’s latest 5.53m (18ft 2in) Interceptor Bumble Bee, which became the first caravan in Australia to be fitted with DSC as standard in October last year.
Weighing up to 2660kg fully-laden, the semi-offroad Bumble Bee is at the upper limit of the weight we usually see in a single-axle caravan. That single axle also makes it more ‘lively’ than a tandem-axle van of similar size, rendering it the perfect candidate for DSC.
Quick to react
However, the problem of demonstrating the system’s effectiveness on the road is that it reacts so quickly that potentially dangerous situations are nipped in the bud before they become an issue.
The best example here is when you’re being overtaken on a freeway by a large B-double truck, particularly when there’s a decent side wind blowing on the overtaking vehicle’s side. The flat wall of the caravan is already under wind pressure when the larger overtaking vehicle not only removes it, but also substitutes a vacuum in its place, suddenly drawing the two vehicles together as though magnetised.
With DSC active, the slight twitch from the Bumble Bee was quickly addressed and the overtaking manoeuvre was completed without drama. In fact, I’m sure many inexperienced caravanners might not even be aware that it happened, as the small ‘grab’ on the opposing tyre might just as easily have been a bump in the road.
AUTOMATIC ON AND OFF
The real interest for a van such as this, that might easily travel main outback unmade roads, is DSC’s automatic on-off feature. Behind the wheel, we were unaware of whether DSC was active or not when we tackled a badly corrugated section of unmade road on Victoria’s Mornington Peninsula and, in my view, this is something that needs to be addressed.
The green ‘system on’ light on the van’s A-frame changes to red when vertical movement is encountered and power is automatically disconnected to the DSC. But other than riding on the A-frame, there’s no way the driver can tell the system’s status under these conditions. It’s a matter of trust.
The full feature appeared in Caravan World #537 May 2015. Subscribe today for the latest caravan reviews and news every month!