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Size does matter and needs to be considered on and off road

We take driving for granted, but large 4WD vehicles demand specialised on-road and off-road skills and an appreciation of the effects of weight and a high centre of gravity.

Safely driving a loaded campervan or motorhome for days or weeks on end over corrugated dirt roads, dodging skittish kangaroos and suicidal emus, is no mean feat.

Add to that the different off-road techniques necessary to conquer slimy clay climbs, steep, rocky descents, giant sand hills, deep mud ruts, icy or croc-infested creeks and incoming beach tides and you have a pretty respectable list of driving skills.

The job isn’t made any easier by the fact that all 4WD van and cab/chassis manufacturers state a single gross vehicle mass (GVM) figure that presumably applies for on-road and off-load conditions. That’s not what the makers of military off-road equipment do.

Most rubber-tyred military vehicles are rated with an on-road GVM and a separate, lower off-road GVM. The need is obvious, when you consider that in some off-road situations, most of the vehicle weight can be on one side, or on one end.

Taking a 4WD light truck – Isuzu NPS, Iveco Daily, Fuso Canter, and Hino 817 – loaded to 6-7.5 tonnes with a high centre-of-gravity (CG)motorhome body into steep, soft or slippery off-road situations is asking for trouble.

Having driven these vehicles with loads on board, we reckon the safe off-road weight for these machines is no more than 4.5 tonnes.

The Mercedes-Benz Sprinter 4WD, VW Crafter 4Motion and 2019 Daily 4WD van-based campervans are more side-slope stable, but also should have restricted off-road GVMs.

We think that all load-carrying 4WDs should have to be plated with an on-road GVM and an off-road GVM.

So, with your weight hopefully under control, we’ll concentrate on some on-road driving techniques.


Be prepared

Before departure it’s important to tie up all the loose ends at home. If there’s a definite departure date for a big trip then plan as if the departure date were two days prior.

The days before departure become inexplicably short and Jobs That Must Be Done take longer than the Best Estimate. Get done with all the city-based work and personal commitments before leaving home.

You can’t drive in a relaxed manner if you’re not sure that the vehicle, its on-board equipment, necessary spare parts and all camping and recovery gear are in top condition. That way you’ve done everything possible to guarantee reliability and reduce hold-ups.

Tyre pressure monitoring is absolutely essential for safe operation of camper vans and motorhomes. Most tyre ‘blowouts’ are caused by an initial, undiscovered leak that reduces pressure and causes the tyre to flex and overheat. Detecting that original leak is what tyre pressure monitoring does.

Everything needs to be packed securely and safely, so there’s little chance of gear coming adrift. Only then is it time to get behind the wheel.

Allow extra travel time if you’re making a rendezvous – have several hours leeway if the meeting point with other travellers is a day’s drive away, or a few days’ extra travel time from the east coast if the meeting point is in Western Australia.

Allowing more time means that you don’t have to drive with ‘pedal to the metal’ to make up time. Cruising along at 95-100km/h in a fully loaded campervan or motorhome isn’t too demanding, but hammering along at illegal speeds is not only potentially expensive and dangerous – or even fatal – but certainly
doesn’t encourage a relaxed state of mind – yours or your passengers’.

Heading off to the bush without a relaxed attitude is a waste of time, money and scarce resources. Up-tight drivers and passengers are the main reasons many dream trips turn into nightmare journeys.

We’re told that if you ‘see’ yourself in a future situation – on top of the dais at an Olympic medal presentation, for example – then you can plan how to get there. If you can ‘see’ yourself and your family back home safe and sound after a long bush trip that vision can be constructive while you’re planning and doing the journey.


Saving on fuel

Up to around 60km/h the largest demands a campervan or motorhome makes on its engine are sufficient horsepower to overcome the rolling resistance the tyres make with the road surface and enough power and torque combination to get it up hills.

Above this speed zone things change: wind resistance horsepower demand increases and by 100km/h is the major power requirement.

Many campervans and motorhomes have trip computers that give a read-out of current fuel consumption, making it easy to find the economical ‘sweet spot’ when touring.

Around town, it’s easy to waste fuel with unnecessary acceleration. In all but unforeseen emergencies, if you have to jump hard on the brakes you’ve wasted fuel. By anticipating traffic flow you can use gentler acceleration that requires only a fraction of full-accelerator fuel demand.

There are some economy driving practices that can make a noticeable difference to your running costs. When your vehicle has to climb a hill there’s a grade resistance horsepower requirement added to rolling resistance and wind resistance horsepower. Let the speed drop off on steep hills and you’ll save
on fuel, as well as on mechanical stress.

Off road you can reduce fuel consumption by keeping revs to a minimum. Use the highest gear that will get the job done, particularly in soft sand.


Living with trucks

Back in the olden days of underpowered
trucks it was easy to pull away from trucks on grades, but now that truck power to weight ratios are typically 8+kW per laden tonne that’s not so easy.

You don’t have to be a rocket scientist to work out that any conflict between a truck and a campervan or motorhome will favour the truck: it’s a simple momentum equals mass times velocity equation (M = mv). So the best place to be is out of the truck’s way.

You can try the high-speed approach to this problem, by blasting past any truck you come across, but this method is in itself potentially dangerous and can be expensive: in fines.

An alternative is the go-slow, no-ego method, where you keep your speed at, say, 95-100km/h in a 110km/h zone. Given that trucks will be cruising at 105km/h they’ll pass you easily enough – on a four-lane road. On a two-laner it’s not so easy and you’re likely to have a rear vision mirror full of truck grille and bull bar.

In these circumstances the go-slow, no-ego truck avoidance driving method requires you to wait for a section of road with a wide shoulder and pull over, letting the ‘Duel’ truck driver get past, after which you can resume your journey.

The go-slow, no-ego method is cowardly, but it works.

The real-world addition to a given trip time isn’t as much as you’d think, because there’s no such thing as a perfect journey: town and school zone speed limits, road works, rest stops and vehicles even slower than yours conspire to extend trip times anyway.

Setting your cruising speed 10 percent below the legal limit won’t extend your trip time by 10 percent – real world experience indicates only around four percent, or less than 20 minutes in an eight-hour driving day.


Look where you want to go

Try this experiment: walk along
a crowded street against the flow and try to avoid walking into people. Tricky isn’t it. We’ll bet that many times, when you make eye contact with an oncoming pedestrian, you both finish up wrong-footing each other, or even coming to a stop, face to face.

Just as when you focus on the eyes of an oncoming pedestrian, if you concentrate your eyes on something when driving: that is what you’re most likely to hit. If you stare at an obstacle, your vehicle will seem to be ‘drawn’ to it.

Stare at a pothole and you’re certain to hit it; or concentrate on the double lines at the apex of a corner and you’re likely to run over the lines.

You should note the obstacle you want to avoid and concentrate on the safe course around it. Your peripheral vision will track the obstacle, but you’ll avoid it.

You can also use peripheral vision to monitor your instruments, simply by noting the needle positions when everything is OK. Your peripheral vision will pick up any unusual readings.



Good anticipation separates experienced drivers and bush travellers from the pack, who jump behind the wheel first, then think about what they’re going to do next.

Our judgment of speeds and distances is generally slightly wrong, according to the Mercedes-Benz research. We tend to underestimate our speed and overestimate the distance we are from an object. That can be a deadly combination, particularly when fatigue and speed-acclimatisation are dialled in.

Anticipation is vital to safe and smooth car driving, but is even more important when it comes to steering a campervan or motorhome. The best road-mannered large vehicle can’t match a sporting car when it comes to response, handling and braking, so planning takes on more importance.

Anticipation properly starts before you get into your vehicle. You need to think about the likely road conditions and the state of the machine.

Extra care is needed if the roads are wet, gravel, or heavily trafficked, or if your vehicle is loaded differently from normal.

However, perception of future problems can sometimes interrupt reaction to more urgent situations: a driver concentrating on a narrow bridge in the middle distance can fail to ‘see’ a stop sign immediately ahead; or if he’s concentrating on a red light a kilometre ahead he can drive through one that’s
much closer.


The ‘Two-Second’ gap

An important contributor to safe driving is leaving sufficient space between your campervan or motorhome and the vehicle in front. If you’re right up on the bumper of the vehicle in front, you’re not leaving sufficient space to allow for any changes. Your only reaction trigger is the brake light in front of you.

Dropping back and leaving at least a two-second gap may open the way for lunatics to cut in, but that’s the occasional price you’ll have to pay for much more relaxed motoring for you and your passengers.

At advanced truck driving schools they often do a little test with professional drivers. When asked what they hate most about city driving, full-time drivers invariably complain about people cutting-in in front of them. To this response the instructor says:

“How much time do you lose every time people cut in – forcing you to brake, downshift and lose momentum?”

The replies vary widely, but the class usually settles into a consensus of about half a minute each occurrence.

“And how many times a day does this happen?” the instructor asks.

Again the replies vary, but the consensus is a maximum of 20 times each day.

“So, in a typical working shift of 10 hours, you lose at most 10 minutes? If this is the biggest problem you’re facing, life’s not so tough after all!”


Handling intersections

The best way to motor smoothly in traffic in your campervan or motorhome is to judge traffic flow and blend in. There’s no skill in rushing up to a red light and braking heavily, but there is in trimming speed early and judging the right approach speed and gear so that you are still moving when the light turns green.

Traffic lights should always be approached with the idea that a red light is a potential green one, but – more importantly – a green one is a potential red one. If you’re looking sufficiently far ahead – and a high driving perch allows you to do that quite effectively in heavy traffic – then you’ll know how long the light has been illuminated.

Traffic light sequences have been worked out so that a vehicle can stop safely within the amber light period, but that calculation is blown out the window if you’re 20 km/h above the speed limit when you spot the change to orange. Try getting off a red light camera charge by saying that the orange light didn’t last long enough!

You can ‘read’ intersections and roundabouts. When approaching a roundabout, for example, it’s best to reduce speed before the intersection to the speed you estimate you’ll be able to use through the intersection. After you’ve cut speed to that level select the gear you can use through the intersection.

By approaching a roundabout in this manner you’ll need only to steer and look as you drive through, instead of braking and gear changing while steering with one hand.


Read the road

‘On-road’ is a generic term that describes surfaces from corrugated, formed-earth graded tracks to concrete multi-lane freeways. Obviously there are different techniques needed to
handle these two surfaces and the myriad types in between.

Reading the road is vital and this ‘reading’ takes into account not only the road but also the vehicle you’re driving. Obviously, a rally car will travel over rough roads much faster than a fully-loaded campervan or motorhome.

There’s a comfortable speed at which you can run over corrugations with the least amount of vibration feedback, but that ‘sweet spot’ cannot be too fast, or you risk losing control.

Generally, around 60-80km/h is as quickly as you’d want to travel on corrugated surfaces and severely corrugated roads may knock your speed well below that. High speeds result in shock absorber ‘fade’ and when the shockers give up so does your steering and braking control.

How fast you can travel on good surfaces is usually down to factors other than road quality. A loaded vehicle will handle differently from an unladen one and speed should be trimmed to suit. Your braking distances will also be affected and that’s another reason for slowing down.

Vision is critical for safe cruising, yet it’s surprising how few drivers slow down at night time or when the road is wet. Night driving in the bush is fraught with danger and dusk is even worse – a good time to make camp until the morrow.


Control fatigue

Fatigue is a killer on our roads. The authorities blame speed for being the number one killer, but fatigue or lack of driver attention is at least as significant. The best driver in the world isn’t much use in an emergency if he or she is nodding off behind the wheel.

Taken together, 84 percent of the events triggering accidents are attributable to the driver, says Mercedes-Benz. Accident statistics accumulated by the company prove that 45 percent of all accidents could have been avoided if the drivers involved noted critical events prior to the accident, then acted without distraction and with correct driving technique.

Ensuring driver attention is best done by having regular breaks and two-hour stints are a good habit, especially if they’re punctuated by a driver change.

One aspect of fatigue that doesn’t seem to get much focus in road safety campaigns is dehydration. Sitting in a heated or air-conditioned campervan or motorhome is a recipe for fluid loss, but because there’s no physical exertion involved it’s easy to miss the onset of dehydration. Water is the best cure and coffee and sugary drinks are the worst.

It’s essential to carry plenty of water inside the vehicle and everyone should drink regularly.


Make allowances for size and weight

Even with the best available camper vans and motorhomes, there are inevitable compromises.

The most obvious compromise is weight: making a large vehicle that can accommodate up to four adults from crawl to 120km/h means building-in distortion-resistant bodywork and chassis; rugged suspensions; traction control; powerful powertrains; strong gearing and big ABS brakes. All that adds up to a four-tonnes-plus vehicle.

When you’re driving a heavy vehicle around town you need to be aware of the momentum that builds up. Drive it like you could an MX5 and you’ll wear out tyres and brakes in short order. On the positive side, the weight can be an advantage, levelling out bumps that have lightweight machines jumping about.

The correct way to drive a heavy vehicle is to build up speed gradually and anticipate where you’ll have to slow down, backing off the gas pedal well in advance. Used wisely, your vehicle’s weight can help produce smooth, jerk-free progress in traffic.

This smooth driving style has measurable fuel economy savings as well. Fuel consumption is related to the rate at which the engine is worked: accelerate hard and drive at high speed and your vehicle will drink fuel faster – much faster.

You can easily gauge whether you’re driving smoothly and with anticipation by checking how often you have to brake. Braking should be necessary only when something unforeseen happens, such as someone cutting in front of you, or when bringing your slowing vehicle to complete stop.

The downside of a tall vehicle is a higher centre of gravity, so the roll-over threshold comes at lower speeds and cornering forces than happen with an MX5. Where a light, low vehicle tends to slide if cornered too enthusiastically, a taller, heavier vehicle tends to trip over.

All new campervans and motorhomes have ABS brakes and some have dynamic stability systems that depower the engine and apply selective braking if the vehicle gets ‘out of shape’.

Those systems are a great safety benefit, but some drivers use them as cornering aids, relying on the vehicle’s control systems to correct over-enthusiastic driving behaviour. What these drivers forget is that dynamic stability control systems rely on tyre grip, at least on some wheels.

If pushed too hard, a heavy vehicle may well lose all grip on loose or slippery surfaces and a short, sharp shock is bound to follow.

Reversing anything with a rear blind spot is a potentially dangerous manoeuvre. If you can’t see everything behind your vehicle get out and have a look. The exercise won’t hurt.


What to do when things get out of shape

Drivers react in a way that they think will get the vehicle back in the groove, but the high failure rate of these manoeuvres suggests that most are doing the wrong thing: instinctive though
it may be.

Let’s look at a common scene: a loaded vehicle is travelling on the crown of a dirt road, flanked by table drains that have been cut deep by a grader. For some reason the vehicle wanders off the crown.

Action: the driver pulls against the steering wheel in an effort to get the vehicle back up on the crown, but it continues to run down the camber of the road, so the driver applies more and more steering effort.

By the time the front wheels hit the table drain they’re cranked over, trying to turn the vehicle to the right, but instead they dig into the soft stuff, the vehicle trips over its own front wheels and rolls to the left. It’s simple physics.

Another common reaction when the vehicle wanders off the crown is to jam on the brakes. With ABS the rig will probably come to a standstill in the table drain, but without the braking stability of ABS or ESC, it’s likely to lock one or more wheels, reducing road grip and a roll-over is likely.

In low-speed manoeuvres, such as trail or sand driving, it’s easy to get into a downhill sideways-slide situation, when the tyres lose grip on muddy or loose surfaces. The instinct to stay in the middle of the track no matter what causes many drivers to turn the front wheels up the hill and a side slope-induced roll-over follows.

The correct procedure in all these side-slide situations is to ‘steer into the slide’. This action preserves vehicle direction and, to a large extent, its degree of heel.

A vehicle that runs straight-on into a table drain or down a steep hill is much less likely to roll-over than one which meets the bottom sideways. Sure, you might find yourself bogged, but that’s better than being on your lid.

Your loaded vehicle’s weight acts through its centre of gravity – that point which is the centre of balance of the loaded machine. The aim is to keep an imaginary pendulum hanging from the centre of gravity within the width of the vehicle. If it swings outside the tyres a roll-over is imminent.


Beware the ‘renter’

We came across one Britz ‘renter’ on the wrong side of the Strezelecki Track corner – probably because he couldn’t remember what side of the road he should be driving on.

The incident ‘only’ cost us a tyre, when we were forced into the gibber pile at the road’s edge and we cheered ourselves with the knowledge that it could have been much worse.

We had a second instance of this behaviour when we stopped for a feed at Stuart’s Well, south of The Alice (great hamburgers, too).

As we left, a ‘renter’ came in the driveway. We steered left, he steered right, we steered further left, he steered further right, until we were facing each other and it dawned on him that maybe he should steer left. He grinned in apology and we grinned back.

The problem of European drivers jumping into right hand drive vans is getting worse, so the educational steps the vehicle rental companies are taking are obviously insufficient. We’re told that rental customers get a thorough run-through on vehicle systems and driving techniques, but it’s not working.


Off road driving

The first consideration is ground clearance. Japanese light-truck and Iveco Daily 4×4 based motorhomes don’t have a problem, but the Sprinter and Crafter do.

Lift kits are available for both these vehicles and those who want go go off-road regularly should opt for a lift.

For occasional off-road use these low-slung vans and cab/chassis are OK, provided you’re very careful in stony country, where a large rock or a shelf could damage engine or transmission sumps.

All 4WD motorhomes and campervans with dual rear tyres are liable to find rocks jammed between their rear tyres. This can destroy both tyres, or, worse, can fly out of their jammed position at on-road speeds, causing vehicle damage or injury to people travelling behind.

Reducing tyre pressures is essential for off-road driving and assessing how much pressure can be tricky in the case of motorhomes. Rather than suggest a target pressure we think it’s easier to opt for a target tyre contact patch size, because an increase in contact area is what you’re after.

The ideal contact patch length is around 300mm (one foot).

Remember, though, that tyres deflated to maybe half their normal pressure are safe at only 40km/h or so and won’t respond to braking or steering as accurately as they do at normal pressure on a high-friction surface.

Most of the serious accidents in dune country involve roll-overs or head-on collisions. It’s easy to roll over if you get side-on across a steep dune. It’s easy to have a head-on collision if you speed up dunes without checking if there’s an oncoming vehicle.

Desert travellers should always have tall ‘masts’ tied to their roo bars, mounting bright red or orange pennants. These help you be seen by oncoming vehicles on dune crests. It’s also essential to set your CB radio on ‘scan’ so that you can pick up transmissions from other convoys that might be oncoming. When you get response, you can exchange GPS co-ordinates, so you know where the oncoming vehicles are.

The best off-road vehicles are lightweights, so don’t take anything you don’t need on a trip. Every kilogram is pushing your tyres into the sand and making the little mound of sand in front of each tyre that much taller. You have to power over those little hills all the time you’re running in sand, so the heavier the vehicle the more the engine has to work.

Clay pans are common in Central Australia and should be treated with a great deal of respect. Many have hard crusts that are solid enough to walk on, but will swallow a heavy vehicle with ease. Getting out of a claypan bogging can be extremely difficult.

Don’t even think about venturing off road without a long-handled shovel; an as-new snatch strap; a pair of shackles that actually fit your front and rear recovery points; a sturdy jacking plate (to prevent your jack heading to the centre of the earth); a tyre pump; an accurate pressure gauge; emergency water and food; and warm clothing.

Sand driving should be a pleasant experience for everyone. That means keeping up momentum without excessive speed or engine revs. The right gear ratio is one that lets the engine work in the middle of its operating range – too many revs and you tend to ‘dig in’ and too few will see the engine ‘lugging’.

In soft sand, low range is a better option than high range. If you select low range you can use the higher main transmission ratios most of the time, but if you need a lower gear it’s a simple downshift to get one. Start off in high range and you’ll be in the bottom of the main box already and a fast downshift into low range is impossible.

If you have manually-operated traction aids, such as across-axle diff locks, use them for straight dune and rocky climbs, but flick them out of mesh when you’ve reached the next flat surface. Steering is difficult on hard surfaces with a rear diff lock engaged and impossible with front and rear diffs

When driving in soft sand it’s important to keep engine revs and the water pump spinning in the mid range, or you risk overheating the engine.

If you cease moving forward, get off the gas pedal, don’t sit in one spot spinning your wheels, or you’ll just dig yourself in deeper.

Keep it straight when climbing or descending dunes or rocky climbs – side sloping hurts. Don’t brake when running down dunes or muddy slopes, or you’ll end up on your lid. Don’t ‘gun it’ too hard up steep sand hills or you’ll get out of control if you hit a decent bump on the slope.

When you do get stuck – we all get bogged sometimes – don’t panic.

Even if you plan to get pulled out with a tow rope or snatch strap, use your shovel to make gradual ramps in front of each tyre.

If you’ve been stubborn about tyre pressures, drop them and try driving out.

Sand ‘ladders’ can be very helpful if you have to get out of a sand bogging by yourself. Some designs have inbuilt shovel action at one end, to help make a smooth ramp in front of each tyre.

Snatch straps work well at very low speed and with very little slack – you don’t need a racing start from a point where the two vehicles are bumper to bumper.

The vehicles should be spaced so that there’s an ‘S’ in the middle of the snatch strap on the ground about one metre in length.

The towing vehicle should move off at normal pace in the highest low-range gear it can use and the bogged vehicle should do the same. Get people clear of the recovery area, in case the strap or an anchor point lets go.

It’s safest if the snatch strap is hooked on to both vehicles without shackle attachment, but some recovery points are too small for that method. Use the biggest shackle that can fit into your recovery point.

Don’t hook a snatch strap over a tow ball: loop it around the towbar; or to the pin that locks a tongue trailer coupling in place.


Mud plugging

The main attractions at off road competition events are usually the mud holes, because people just love seeing competitors deal with bottomless black ooze. It’s not so amusing, however, when you come across the same sort of stuff on an off-road trip.

Mud driving used to be part and parcel of off-roading, but mud is rarer stuff now – and not just because of drought. The reason we encounter less mud these days is that most roads and trails are closed quickly by councils or other authorities in response to wet weather.

However, one day you’re going to encounter a muddy situation, even if it’s only the steep bank on the other side of a water crossing, made muddy by water pouring from vehicles as they clamber up the slope.

Another common mud situation is caused by overnight rain, turning yesterday’s dusty tracks into strips of mud.

A sudden downpour on a country road or bush track can create a driving hazard, because clay or dirt surfaces turn into a paste that has the friction quality of soap.

You need to drive very carefully in these circumstances, staying up on the ‘crown’ of the road, to avoid sliding into the table drain. Keep it smooth.

The dark grey soils that are common around rivers, creeks and channels – even dried up ones – are notoriously difficult to handle when wet. The best driving option in black soil country is: don’t. Wait a day or so, if you can.

Another possible mud situation is a section of track that runs across low-lying ground and has filled with water. Before driving into it, have a good look for signs of damaging debris, such as bits of tree branch or sheets of iron that other travellers have used to extricate themselves. Clear this tyre-destroying material first, or make sure you can drive around it.

Driving up a muddy slope is similar to driving up a sand hill, because both surfaces cause wheel spin that needs to be controlled. A short, muddy slope doesn’t usually pose much of a hazard, but a long climb can be fraught with danger.

Tyre ruts normally serve to keep your vehicle aligned up the slope, but a climb without ruts offers no guidance. It’s possible to power slide off such a track, into trees, or over a steep edge.

It’s essential that you engage whatever traction aids you have – centre diff lock or across-axle locks – before you attempt the climb.

As with sand driving the trick is to maintain momentum in the highest gear that delivers enough power, without going so fast that your vehicle leaps all over the place.

Another common factor between sand and mud driving is the need to lower your tyre pressures. Lower pressure means a larger tyre contact patch that should provide more grip and a more flexible tread area that can mould itself over irregularities in the surface.

Although climbing a muddy slope is similar to conquering a sand hill, coming down a greasy slope is quite different from surfing the other side of a dune. Sand slows a descending vehicle, but mud does not. The momentum you needed for the climb is your enemy on the descent. Many a vehicle has come down a mud slide too fast and wrapped itself around a tree.

You need to come down a slippery hill with great caution and at the lowest possible speed. Keep your traction aids engaged and avoid heavy braking that could lock wheels and start an uncontrolled slide.

For serious mud work you can’t beat driver-controlled, across-axle differential locks, or self-locking diffs. With the centre diff locked and front and rear axles locked up your wheels will rotate at the same speed, regardless of tyre grip. This ensures forward progress in all but the deepest quagmire and prevents damaging slip and grip wheel spin that can snap axles, diffs or CV joints.

Back in the olden days we used to carry mud chains, but these are frowned on by track maintenance people, except at The Snow.

Keep it safe and have fun!



























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