ESC vs DSC: Sway control system test
We carry out the first real-world marathon test between the Al-Ko and Dexter sway control systems.
If you have never experienced that uneasy, cheek-tightening feeling of caravan sway, you probably haven’t been towing caravans for long enough.
The laws of physics tell us that a trailer weighing several tonne, hanging off your towball, will make itself apparent one day, in one way or another – through overtaking trucks, side winds, avoiding roadkill or other road users.
But there’s no reason to panic. If you are an experienced vanner, have ever ridden a trail bike, or have rallied or rally-crossed, you will have coping strategies which include making quick corrections in slow motion.
If you haven’t, there’s now Al-Ko Electronic Stability Control (ESC) or Dexter Sway Control (DSC) to help. One or the other now come standard on many vans or can be optioned at a cost of about $1100. And both do much the same job of bringing an errant caravan to heel, albeit in different ways.
Which sway control system should you use?
So which is better for you, your level of experience and the type of caravan travel you do? We set off to find out. In what was, unquestionably, the longest comparative test of the two rival systems, we took two similar Bailey Rangefinder caravans towed by identical Toyota LandCruiser 200 Series Saharas about 8300km across Australia from west to east, incorporating more than 2200km of unsealed roads ranging from well-graded outback highways to corrugated roads, plus smooth and broken bitumen.
Al-Ko ESC was born from mechanically-operated Al-Ko ATC, which has been used on almost all European caravans for the past eight or so years and operates with override brakes.
ESC, which operates through the caravan’s electric brake system, was developed in Australia and, after its launch in late 2012, was quickly adopted by the caravan industry. A prime mover in its rapid take-up was the belief by the industry that it would help combat the inherent fear of loss of control that many new caravanners had and may, therefore, encourage people to invest in larger caravans. The industry also believed it would encourage more women to tow and would lead to more couples travelling further afield more often, although there are no statistics to confirm its impact in these areas.
Most caravan manufacturers now offer ESC or DSC as either standard fittings or options on larger vans, usually above 2t Tare.
From the outset, Al-Ko insisted that ESC had to work in conjunction with the Al-Ko electric brakes and axles that, until then, were fitted to many Australian caravans.
Drawing its power from the tow vehicle, via its conventional 12-pin plug or a separate Anderson plug, ESC activates all four caravan brakes evenly when two accelerometers in its caravan chassis-mounted ‘black box’ sensor decide that the van’s ‘yaw’ (side-to-side movement) verges on hazardous.
DEXTER SWAY CONTROL
Although well-established in the US, Dexter Sway Control is the new kid on the block in Australia, arriving two years after ESC in the third quarter of 2014.
Unlike ESC, DSC draws its power from the caravan’s battery and does not have to be plugged into the tow car for its anti-sway feature to work.
Again unlike ESC, it also monitors vertical movement as well as trailer ‘yaw’ through its motion sensor, permitting it to switch off when severe offroad conditions are encountered, to avoiding nuisance braking. It then switches back on once it detects no further vertical movement over a similar five-second period.
The idea is that you will retain – or regain – DSC if you travel on relatively smooth unmade surfaces, when speeds are likely to be higher, but will not have wheels locking selectively on rough ground.
DSC also has a ‘Sleep Mode’ – after 30 minutes of no activity (movement, braking, etc.) it goes to sleep, reducing power consumption to a negligible level, but wakes up as soon as the brake pedal is touched.
As we were planning to join Bailey Australia on its pioneering 8300km West2East test run of two new locally-designed and built Rangefinder caravans, we saw the perfect opportunity to line the two systems up for the longest real-world caravan sway control test ever conducted.
THE TOW CARS
We approached Toyota Australia, which was delighted to make two identical, brand-new LandCruiser 200 Series Sahara diesel models available as tow tugs for the vans.
The two caravans were as even as we could make them – an 1820kg Tare weight 6.66m (21ft 10in external) Rangefinder Gemini family bunk van and a 1970kg Tare weight 6.93m (22ft 9in external) Nebula ‘couples’ van. The empty ball weights were both 160kg.
Each van had its twin 105L fresh water tanks full and each carried some cargo properly distributed.
The Gemini was fitted with a conventional 50mm ball hitch and Al-Ko axles, brakes and ESC, while the Nebula was equipped with a 360° Vehicle Components DO35 offroad hitch and Dexter axles, brakes and DSC.
However, a key difference between the two vans that slightly blurred our findings is that the Gemini had a front island bed/rear bunks/ensuite layout, while the Nebula’s layout was based on Bailey’s best-selling British caravan, the Pamplona, with a large front lounge, rear bedroom and a bathroom immediately over the axle line. This means its axle set and wheels must be slightly forward, so its rear overhang is a little longer than the Gemini’s. As a consequence, the van is inherently more ‘frisky’ than the Gemini and more likely to wag its tail when affected by road surface or side winds.
ON THE ROAD
Leaving Shark Bay, WA, the western-most caravan-accessible point of Australia, we spent the first 1300km of our test on good quality bitumen. Despite cruising at up to the 110km/h speed limit, the Gemini’s ESC never announced its presence. However, travelling at speed in blustery conditions approaching the end of the bitumen at Laverton in central Western Australia, we felt an occasional but gentle ‘hiccup’ in the Nebula rig.
It was so gentle and short-lived that we initially thought it was the Toyota’s diesel engine coughing down a dose of dodgy fuel but, eventually, we realised that it was only noticeable when either one of the two less-experienced caravanners in our party was at the wheel, although there was no evidence of dramatic trailer sway.
We concluded that the DSC sensed this nervousness, which was heightened by the Nebula’s ‘axle-forward’ stance. This happened far less when the more experienced drivers were in charge, as they were less tense at the wheel and worked with, rather than against, any perceived sway.
If you are looking for an absolute hands-down winner here, you may be disappointed, but here is a summary based solely on our experience:
Both systems could save your life in a critical situation
Neither system should endanger your life by acting inappropriately or unexpectedly
Both systems will work with, not against, your tow car’s skid and/or trailer sway control, if fitted
Al-Ko ESC cuts in later and harder than DSC on extreme caravan sway on bitumen, leaving something in hand for the experienced caravanner
Dexter DSC intervenes earlier and more gently on bitumen, taking over sway control from the less-experienced caravanner
ESC did not activate annoyingly on unsealed roads and mild corrugations, making it a good system for on-road caravans encountering unsealed roads in generally good condition
DSC remained active on unsealed roads and mild corrugations for longer than we expected and did not switch off until a series of noticeable corrugations was encountered. When it did switch off, it was ideal for heavy corrugations, making it a good choice for offroad caravans on such roads.
So, based on the above, we concluded that ESC’s later intervention might suit an experienced on-road caravanner (who is probably going to encounter fewer critical sway situations).
On the other hand, DSC is the sometimes-welcome ‘nanny’ that many inexperienced caravanners will find great comfort on major sealed and unsealed roads, yet will leave the offroad traveller to their own devices when the going gets rough.
The full feature appeared in Caravan World #543 November 2015. Subscribe today for the latest caravan reviews and news every month!