Like many southerners, we’re caravanning north to warmer climes, cruising at a true 90km/h. We have our new Trakmaster Pilbara caravan in tow behind a Land Cruiser 200 Series diesel to escape Melbourne’s encroaching winter. And so, it seems, is everyone else!
Most of us are time-poor, with more things to see and do in less time. Fortunately, the availability of tow vehicles that can match other highway users for speed has raised realistic highway speeds for caravan travellers.
Whereas caravanners were once ‘roadblocks’ that travelled at a maximum of 75-85km/h, they now move 10-15km/h quicker on average – usually on better roads – but are still among the slowest vehicles on the highway.
But is towing at such speeds a good idea, not just from the safety aspect, but how it hits your hip pocket?
Ignoring the obvious increased risk of losing control due to fatigue or through a sudden avoidance manoeuvre, there are practical reasons why towing above a true 90 km/h is not a good idea, regardless of the speed limit.
Let’s deal with your hip pocket first. A large caravan usually requires a large tow vehicle and together they have to move a lot of air to maintain cruising speeds.
While our Land Cruiser has relatively low friction highway-pattern Dunlop GrandTrek tyres, and those on our Trakmaster are only moderately meaty General Grabber AT2s, many rigs have rubber more suited to mud than bitumen. This means they are more prone to overheating due to tread-block movement, even in the high 20°C ambient temperatures we are experiencing during our travels, but which in mid-summer may be close to 60° on the road.
In these conditions, those big-block tyres will build up even more internal temperature as their tread blocks squirm. So the hotter it is and the faster you travel, the greater the potential for tyre failure, particularly if your tyre pressures are not at their optimum. If they are like those on many caravans, they will be more than five years old; the rubber will have been exposed to UV rays, gone hard, and thus will be more prone to heat gain and failure.
Towing At Speed
Now let’s talk speed. All engines have an ideal operating range where the torque, or pulling power, is at its peak. In most diesels, peak toque is delivered between 1700 and 2200rpm, but depending on your car’s gearing, maintaining this in top gear may mean travelling faster than is ideal for fuel economy.
The latest Land Cruiser 200 Series that we’re towing with has the same 4.5L twin-turbo V8 diesel engine of its predecessor, but it has been tweaked so that peak torque is now reached from just 1600rpm. This means that you can tow a caravan weighing up to 3500kg in fifth gear instead of sixth more economically at a lower speed, whereas with the previous engine you had to travel faster to stay in the engine’s ‘sweet spot’.
Don’t fool yourself: holding it in sixth gear at a higher speed to make the most of that extended torque range will cost you at the pump. It might only be one or two litres per 100km, but that $3 or so can add up to a significant amount if you are on a big lap of the continent.
Even more important in remote areas, such as the ones we are planning to explore during our trip, is that extra fuel burnt will reduce your travelling range in between tank fills. This becomes critical in areas where pumps can be 500-600km apart.
My suggestion is simple: wipe off 10km/h.
By towing at around 10km/h or more below the prevailing speed limit, you will not only save fuel, but blend into the traffic better, allowing faster vehicles to overtake more safely and not holding up fast interstate overnighters and B-doubles on hills.
By following this rule, you will also travel more safely. Many travellers have little or no experience of towing, let alone steering a heavy tow vehicle and wind-affected and often poorly loaded caravan for many hours on end on unfamiliar roads.
So when the rear of your van is sucked into the vacuum of a huge B-double truck as it passes, or when you get the wobbles from a sudden side wind or a change of road surface, things will happen slower and more controllably if you are not travelling so fast.
Here, fortunately, advanced technology such as AL-KO’s ESC (Electronically Stability Control), is available to come to your rescue if things go wrong.
By detecting a dangerous level of sway and applying your trailer or caravan brakes progressively to minimise its ‘wag’, ESC works as an unseen but welcome guardian angel to come to your aid automatically when you most need it.
We have sway control on our Trakmaster, but if it comes into play we know that we are doing something wrong: we are going too fast; the caravan is badly loaded; or we are not concentrating.
However, there will always be situations where, no matter how prepared and experienced you are, you may need to take action to avoid the mistakes of others, or unforeseen road hazards, so there is every reason to have sway control fitted to your current or next caravan.
Off the bitumen there’s another real hip pocket problem associated with high towing speeds: stone damage.
Experienced travellers can tell at a glance how fast you’ve been travelling by the pockmarks on the front of your van. Most manufacturers’ front stone shielding should cover you for up to 60km/h on an unsealed road, with the line of stone damage rising about 20cm for every 10km/h above that. It’s easy for your speed to creep up on a long stretch of unsealed outback highway, but you will pay for it, whether in stone damage, or with the impact that an unexpected pothole can transmit to your caravan.
Lots of checkerplate secured to the front of your may not be the answer as it has been known to reflect stones back onto the rear window and tailgate of the tow vehicle. A padded zip-on ‘bra’ (fitted optionally by manufacturers such as Bailey on its locally built Rangefinder caravans), a truck-mesh shield on the A-frame, or an after-market stone shield that deflects stones off your tyres – in short, something that will catch or deflect stones at the slowest possible speed – will all help.
But if you are travelling slower, so are the stones…