Every 4WD, no matter how high it rides, has limits to its ground clearance and to the depth of water it can drive through. You will need to develop a sense of what those limits are for your vehicle. In general, the biggest wheels and the shortest wheelbase give the best ground clearance. Short-wheelbase vehicles are also able to turn more tightly than long-wheelbase ones, making then more manoeuvrable.
Remember that ground clearance doesn’t remain constant. If you drive over a hump, the front wheels will be on one side of it while the rear wheels are still on the other. If the hump is steep enough or you are driving a long wheelbase 4WD, your vehicle may get grounded on it and turn into a seesaw, with all four wheels hanging in the air. The technical term for what rules whether or not you will get stuck is the ‘ramp angle’, and it is measured from the chassis at the centre of the wheelbase down to where the front and rear wheels touch the ground. Obviously, the shorter the wheelbase the smaller this angle will be, and the steeper the hump that can be tackled safely.
Another thing to watch out for is any overhang at the back of the vehicle, such as a bumper or tow hitch. If you start up a steep slope, this overhang might scrape on the ground and get damaged. Worse still, if you are reversing down such a slope, the overhang may crunch into the ground at the bottom and hold you fast.
Also at issue is the amount by which the axles can ‘articulate’, or move up on one side and down on the other side of your vehicle at the same time. On undulating terrain, articulation governs how well your vehicle can keep its wheels on the ground and thus retain traction.
No matter where you choose to venture, each new landscape will present its own unique set of properties. Even familiar places can assume an unfamiliar guise following rain or excessive use. The fundamentals of successful off-road driving are to be found in the ability to recognise each situation for what it is and tackle it accordingly.
Remember, whatever the terrain, 'nice and easy' does it. If someone is ahead of you, learn from them. Learn which way works (or doesn’t) and use their experiences to help you. On the other hand, if you’re the first to undertake the challenge, plan your actions beforehand and don’t be afraid of making several attempts. Better to get across safely in one piece than be marooned miles from anywhere. If you think an obstacle or a tricky piece of terrain is about to test your vehicle’s limits, get out and check it on foot first. This way you will be able to find the best route, and also find any particular hazards that you need to avoid.
In very rough uneven terrain, use low-range four-wheel drive. This will lower ground speed, reducing the vehicle’s bounce, and will give better steering.
• Select the appropriate gear before attempting any obstacle.
• Don’t change gears in the obstacle unless it is into reverse to back out.
• Drive steadily with a sensitive right foot on the throttle.
• Keep good throttle control to reduce wheelspin.
• When wheelspin occurs, always decelerate; never accelerate.
As an old 4WD colleague of mine always says, ‘Go as slowly as possible, and as fast as necessary.’
The driver of a 4WD cannot see under or on the left side of the vehicle so use your common sense and do not drive in conditions that you are uncomfortable with.
Use one of your passengers outside the vehicle to act as a marshal to help negotiate difficult sections. If they place themselves where they can see all four wheels and check the ground clearance, they can guide you through. It’s better for the marshal to use hand and arm signals rather than calling out: that way the marshal’s instructions are easily understood amid engine noise.
When reversing your 4WD use a marshal or get out and have a careful look at what is back there. Many drivers have damaged the rear and underside of their vehicle or dropped off a bank because they made an assumption that turns out to be incorrect.
Training the marshal
Your passengers may have no appreciation of any of the finer points associated with four-wheel driving; so if you want to use them as marshals you will have to explain to them exactly what you want them to do. They must be able talk to you and tell you what is going on where you can’t see. To be able to do this you must have the windows open on both the driver’s and passenger’s side of the vehicle. If they are required to give hand signals make sure they stand in a position where they can both see what is going
on and be able to be seen by you. Where they are required to give you an indication of how far you can reverse your 4WD ask them to hold their hands apart and slowly bringing them closer together as you reverse, finally clapping them together indicating you should stop. It is absolutely useless having a marshal 20 or 30 metres away from your 4WD with his hands in his pockets yelling at you to ‘stop’ just as you are about to drive over a bank.
If you intend to take a friend, partner, wife or husband out on a regular basis, give them some training on a simple little track close to home.
DON’T GET STUCK BY A HIDDEN HAZARD
Avoid hazards. It sounds obvious – but not all hazards are obvious.
Long grass, tussock, thistles, and other groundcover can hide logs, big rocks, ditches, or short vertical banks. The result of striking a hidden hazard can range from simple tire damage, to a front suspension removal, without even undoing the bolts! It is when this happens that seat belts suddenly prove their worth.
It’s not always possible to know where these hazards are – there is always an element of luck in four-wheel driving – but experience and keen observation will help minimise the risk.
The general lie of the land, noting the direction of likely water run off, will tell us where to expect a drain, ditch or washout. Vegetation is a good indicator. A line of weeds and bushes growing more vigorously than the general groundcover can indicate a waterway. And small banks often stop wind blown seeds, encouraging the growth of intermittent shrubs or trees.
Knowing the geology of the area will highlight the possibility of scattered rocks, and old stumps or other signs of early logging should sound warning bells about fallen logs. Look out for old fence posts and steel standards as it has been common practice for old fences to be partly ripped out and the wire left on the ground to get wrapped around a wheel or prop shaft. This is the time when you need the big wire cutters. It is possible to get long grass and weeds wrapped around the prop shaft also.
But the best way, as always, is to take it slowly - even have someone walk ahead if conditions warrant.