DRIVING/TOWING - TOWING
The correct towing technique can make the difference between the holiday of a lifetime or a nightmare.
We’d just fuelled up at the Marla Roadhouse, after a run up the Oodnadatta Track and were enjoying a cuppa and a bite to eat, when in pulled a brand new Ford Territory, hauling a sparkling two-axle caravan. We made some obvious remarks about new retirees while we watched them fuel up and head off, up the bitumen.
A few minutes later, we headed north as well, but we hadn’t gone far before we came across slowing traffic and flashing lights. Tell-tale skid marks and dirt scattered across the road suggested mayhem and then we came upon the wreck.
The retired couple’s new Territory and van looked decidedly used, after a major roll-over, with most contents spread out over the desert landscape. The occupants weren’t hurt, but they were badly shaken by an experience that took only seconds and must have felt like an eternity at the time.
We surmised that the driver was distracted and the vehicle wandered onto the dirt verge. At this point, the skid marks indicated panic braking that caused the wheels running in the dirt to lock and a sudden jack-knife, followed by a roll-over, was inevitable.
You can’t blame motorists entirely for the generally poor standard of trailer towing in Australia. Contributors are State and Territory governments that have consistently avoided making motorists test for special licences to tow trailers. If you want to tow a trailer behind a heavy truck you need proof of solo-truck-driving experience, professional training and a special licence, but anyone can hook up a caravan behind a 4WD.
On top of that there’s an Australian Design Rule that covers truck-trailer braking balance, but motorists are free to dial up what they feel is the ideal braking balance between a 4WD and its trailer.
One of the most potentially dangerous manoeuvres you can perform with a trailer is washing off speed in a hurry.
‘Jack-knife’ is a well-known term, but is often misunderstood. A jack-knife occurs when the rear axle of the towing vehicle locks up and skids sideways, letting the trailer and the tow vehicle slam together like a pen-knife blade being folded away.
Jack-knife occurs in an eye-blink and normally cannot be corrected by the driver.
ABS is a handy tool for avoiding Jack-knife.
‘Trailer swing’ is different and occurs when the trailer axle locks under braking, or slides sideways because cornering speed is too high. Trailer swing can be corrected by easing up on the brakes and steering straight ahead, if possible.
Braking should be done with the vehicle and trailer in a straight line, wherever possible, because any angularity can upset the alignment of the combination.
Heavy braking when towing should be avoided, because a 4WD and a big trailer don’t make a very stable combination. You can avoid most heavy braking situations by anticipating road and traffic conditions.
Most new trailers come with electric trailer brakes or hydraulic over-run brakes that allow adjustment for brake application timing.
If you’re unsure how to adjust the reaction of your trailer brakes, ask your trailer supplier to explain the process.
Brake adjustment needs to be maintained and your supplier can advise the best way to achieve this. If your trailer pads or linings are worn or aren’t adjusted the braking effect will be delayed, weakened, or even non-existent.
Check out this accident video and you’ll see how anticipation and ABS/ESC braking might have avoided a disaster.
Keep It Smooth
Anticipation is the key to smooth trailer towing. In towns, a red light is a potential green one and, more significantly, a green one is a potential red one. Your aim should be to keep the combination moving, by easing off the accelerator on the approach to a red light, anticipating the change to green.
Don’t race towards a green light and then have to brake suddenly when it changes to orange.
Hill starts take time when you’re towing, so you can avoid them sometimes by trickling slowly up a hill, rather than sitting on the tail of the vehicle in front. With some luck the red light at the crest will change to green before you get to the tail of the traffic column.
Smooth driving is vital on the open road, as well, letting you maintain a steady speed, with a minimum of braking and hard acceleration.
Overtaking other vehicles when towing is a much slower operation than when you’re running solo. Allow plenty of time for your journey, so you’re not pressured into risky overtaking manoeuvres.
It’s quite common to find a big truck up your clacker when you’re towing. Most 4WD drivers with trailers don’t run as fast as truckies, who are used to the road and have time pressures on them. Leave your ego at home and let the trucks go by.
On an uphill section that slows a truck, which has already overtaken you, don’t overtake even if you can, because you’ll have him back on your tail when the road levels out again. Just tuck in behind him on the hill and enjoy the scenery.
When running off hills, use the gears and engine braking – even in an auto – to control your speed. You’ll reduce brake wear in the process.
It doesn’t take long to find out how your trailer ‘tracks’ behind your 4WD. After a few right-angle corners and roundabouts you’ll know from looking in your mirrors how much ‘cut-in’ the trailer has when cornering and you’ll make a steering allowance for it when turning.
On the open road most corners have wide radii, so cut-in isn’t a problem. The important factor in these conditions is judging the appropriate cornering speed and steering wheel movement so the combination travels smoothly around the corner. It’s important to avoid steering corrections mid-corner, because a 4WD and trailer won’t behave as predictably as a solo 4WD will in the same conditions.
Dirt or muddy roads magnify the instability of a 4WD and trailer combination, because the grip levels at the tyres are markedly reduced. It’s time to drive like you’re on ice, building up and washing off speed very gradually and avoiding any sudden manoeuvres.
Driving your trailer in off-road conditions is a potentially disastrous exercise. We’ve lost count of the abandoned trailers we’ve come across in the scrub. Most of the drama is caused by drivers who don’t appreciate what the trailer is experiencing.
Off-road trailer hauling is largely a matter of suiting horses to courses: leave hard-core travel to trailers with rugged construction and low payloads and confine lightly-built caravans to low-speed, moderate driving conditions.
Slippery, downhill slopes are a potential disaster site and are best avoided. You may well need to ‘belay’ the trailer using an uphill vehicle’s winch, to stop it overtaking the towing vehicle.
Overtaking when towing used to be impossible in the days when tow vehicles lacked power and torque. However, modern towing 4WDs have ample power and torque to give performance similar to that of yesterday’s unladen vehicles. That’s where the trouble starts.
If you’re towing with a turbo-diesel wagon that has more than 200kW of power and 500Nm of torque you have enough performance on tap to travel at 160km/h. Hopefully, you’re not that stupid, but the potential is there.
Nearly all drivers feel unsatisfied if they’re being ‘held up’ by a slower-moving vehicle. When overtaking isn’t an option that means ‘putting up with it’ until what looks like an overtaking opportunity appears. Then the Red Mist settles over the eyes and the foot goes to the floor.
Often, this manoeuvre is undertaken safely, but sometimes it isn’t and the consequences usually involve multiple vehicles.
Before any overtaking manoeuvre a towing driver needs to think about the purpose of the move. The first question should be: do I need to overtake?
If you’re ‘forced’ to travel at 10km/h less than your desired cruising speed; what will be the consequences? In one hour of travel, you’ll be 10km short of where you would have been at the higher speed. Is that critical to the rest of your trip? On the plus side, you’ll almost certainly save some fuel by travelling at 90km/h, say, than at 100km/h.
Incidentally, that ‘lost’ 10km can be covered in a little over six minutes of travel time. Hardly worth risking an accident for, is it?
When we’re ‘stuck’ behind someone who’s travelling more slowly we discuss alternatives to overtaking. Is it time to have a cuppa? Is it close enough to lunch time? Do we need a ‘comfort’ stop? Are we going to exit this road in a short while?
How many times have you been overtaken by someone who risks life and limb – including yours – only to pull over into a rest area or turn off the road a short time later. How about the loony who overtakes and then slows down once in front of you?
Before pulling out in any overtking manoeuvre, check your mirrors carefully to ensure that you also aren’t about to be overtaken.
Use your indicators to signal your your intention to overtake, but don’t trust the ‘safe to overtake’ blinker singals from the other vehicle: make sure you can see that’s it’s safe.
When being overtaken by another vehicle, you must consider the other party and realise that speeding up in such a situation is illegal, because of the fact that it risks lives. It’s in your own interests to let the passing vehicle get by as quickly as possible.
As a courtesy, you should gently slow down, once the overtaking vehicle is beside yours, to make the overtaking manoeuvre quicker and safer. That slowing may need to become braking action, if the overtaking driver has miscalculated.
Before any overtaking manoeuvre it’s highly preferable that the driver of the vehicle being overtaken knows your intentions. If the vehicle displays a CB channel on the rear, call it up. A truck can usually be reached on Channel 40.
Speaking of trucks, if you happen to be in road train territory – that’s anywhere west of the major east-coast truck routes – be extremely careful when overtaking one on bitumen.They’re up to 50 metres long and can be travelling at 90-100km/h.
Don’t even think about overtaking a road train on gravel, unless the road is very wide and not too cambered; the wind is blowing dust away from the trailers, leaving you a clear view of the road ahead and the truck driver has responded to your radio call.
Even then, you’re likely to drive through a stone shower, so weigh up whether it’s worth it.
Most towing drivers know that the combination of vehicle and trailer doesn’t accelerate or brake like a solo vehicle. However, they’d be horrified to know just how long they need to be on the ‘wrong’ side of the road during a typical overtaking manoeuvre.
The Caravan Council – www.caravancouncil.com.au – has kindly provided the following calculations that show how long you’re exposed to a potential head-on collision.
The drawing depicts a car-caravan combination [V1 & V2] over-taking another vehicle [T] . The drawing is not to scale, as LA and LD are relatively much longer than LV and LT.
The most influential factor in determining “L” is the speed of “T”, which sets the required acceleration and speed of “V” – in order to over-take safely, and move back into the left lane.
The relative speed between “V” and “T” is also instrumental in determining the over-taking distance required: along with the time spent in the “wrong” lane.
Of course, the “LA” and “LD” distances and times are much longer than these “just to clear” figures
The distance just to clear a 5m-long vehicle (with a 15m-long combination), allowing a total [LA + LD] Safety Factor of eight times the length of the combination, is, in this example, 120 metres. At the following relative speeds the ‘exposure’ varies greatly:
30 km/h (9 m/sec) 20 + 120 metres Time Taken: 16 seconds
20 km/h (6 m/sec) 20 + 120 metres Time Taken: 23 seconds
10 km/h (3 m/sec) 20 + 120 metres Time Taken: 46 seconds
As the speed of “T” increases, the ‘exposure’ increase at an exponential rate.
Note that ‘air-drag’ increases with the square of the speed and the available acceleration rate is reduced; the ‘inertia’ of the combination also increases with the square of the speed and, more alarmingly, the engine power requirement increases with the cube of the speed.
Many 4WD drivers have a fear of reversing trailers. The fear usually comes from a lack of experience, so the easiest way to eradicate that fear is to practise
reversing in a controlled environment – a deserted shopping centre car park is ideal.
There’s no point practising reversing looking backwards through the rear window – you must use the door-mounted mirrors. There’s no point developing a reversing technique based on screwing around in your seat and looking through the back window, because if you have a full load in the back of the wagon
you have no vision. Similarly, if you’re towing a caravan, you can’t see anything but the front of the caravan through the back window.
Reversing using your mirrors is simply a matter of practice and, like riding a pushbike or skiing, once gained, the skill stays with you.
Some newer vehicles have ‘trailer assist’, which is a reversing program that takes the guesswork out of this sometimes difficult exercise.
Use the Mirrors
The door-mounted mirrors are your only reliable means of seeing backwards when you’re towing a trailer that blocks your rear window view. Most 4WD mirrors are set wide enough to give adequate rear vision along the sides of a camper van, but if they’re not they can be supplemented by clip-on extensions
that are wider-set than the standard peepers.
Concave ‘spotter’ mirrors are useful, because they give a wider view to the side and the rear than standard mirrors. They distort distance in direct proportion to the increase in viewing area so they’re not reliable for assessing distances, but are a boon for obtaining the big picture.
Spotters normally provide a viewing area that includes the trailer tyres, so they’re handy for checking tyre condition as you trundle along and for positioning the trailer wheels when reversing or when off road.
It’s vital that whatever you’re trailing – boat trailer, caravan or camping trailer – remains balanced, with any payload evenly distributed fore and aft of the axle(s). You shouldn’t load heavy objects – spare wheels, batteries, gas bottles and water tanks – in places other than those selected by the trailer maker for that purpose. Heavy items not only have the potential to cause damage to the trailer chassis and bodywork but can cause severe loading balance problems.
Excess weight on the tow ball can stress the coupling and the tow bar, while also overloading the rear suspension and lightening the load on the steering axle.
Too little weight on the tow ball can cause trailer swing and, in extreme cases, lighten the rear axle of the 4WD to the point where it lacks grip.
Instability is certain in both these poor-loading cases.
If you want check the safety and legality of your towing combination, check out our calculator.
Trailer Tyre Pressures
The weight on a trailer axle and the size of the tyres dictate what pressure should be inside its tyres. Speed is another factor, but if you tow at speeds over 110 km/h you’re in no man’s land.
The friction between the tyre tread and the road and the friction caused by flex in the tyre casing cause heat build-up in a tyre.
The correct air pressure guarantees sufficient air volume to prevent too much flex and tread-road friction, but too much air pressure makes a tyre rock hard and liable to carcase fracture. The harsh ride of an over-inflated tyre can also cause damage to the trailer and its load.
A full-sized 4WD tyre mounted on a lightweight camping trailer axle may need only 18 psi pressure, while a small-diameter boat trailer tyre may need 40 psi. It’s a matter of taking advice from the trailer maker and your tyre supplier.
When in conditions that dictate a drop in the tyre pressures on your 4WD, drop your trailer tyre pressures by the same percentage.
It’s surprising how many 4WD owners try to tow, winch or snatch a bogged vehicle and trailer as a single unit. If the trailer is uncoupled the 4WD often can be simply driven out. Then it’s time to recover the trailer.
A trailer is easiest extracted by attaching a tow rope to the drawbar and pulling it free, gently. The jockey wheel is nearly always an obstruction, so leave it folded away. You can keep sand and mud out of the trailer coupling by wrapping the coupling tightly in a heavy bag or tarpaulin.