Four-wheel drive vehicles can master seemingly impossible terrain with ease, but they can get hopelessly stuck in a flat field of grass. While the vehicle and the choice of tyre are absolutely critical to successful off roading, it is ultimately the skill and competence of the driver that decides between an enjoyable drive and embarrassing failure. Here I explain the essential basics to put you on the right track to tackle some off-road situations with confidence and in safety.



Intro

The starting point is to thoroughly familiarise yourself with the vehicle by reading through the owners manual. Some vehicles are permanently in four-wheel drive mode, others have the option of selecting two or four-wheel drive according to the terrain. The manual can often tell you things about the vehicle that you probably didn't need to know before now. For fuel economy reasons alone it is preferable to select two-wheel drive for everyday road driving if possible, unless weather conditions dictate otherwise. Check if the vehicle has free wheeling hubs, and thoroughly understand the procedure for engaging, if applicable, and selecting low ratio transmission where fitted.



Hilly Stuff

Steep hills are the most common off road hazard and are potentially the most dangerous. Always travel in a straight line up or down a hill and check in advance to ensure that there is a clear exit at the top or bottom. There's no use powering to the top of a steep hill to find an obsicle in the way! When tackling an uphill section normally you would select second gear, engage the low ratio gearbox (if fitted) and use a short run up to gain a little momentum before you hit the hill. Try to gauge it so that you crest the hill at walking pace. This is the speed you should adopt for general off-roading in the interests of the vehicle, comfort and safety.



Never try to change gear or direction once committed to a hill, and be prepared for the loss of vision as the sky fills the windscreen on a steep climb – that’s the reason you checked the hill beforehand. If you lose forward momentum, hold the vehicle on the brakes, quickly select reverse gear and let the engine braking control the descent while you look over your left shoulder holding the wheel with one hand to avoid oversteering. Do not use the accelerator or try to control the decent with only the brakes.



Driving a steep downhill section needs first gear, again in low ratio (if fitted). Again check the terrain in advance making sure the hill isn’t so steep that the front of the vehicle will bury itself in the ground at the bottom. This is especially important if your vehicle is normally road-going as bumpers and splitters can reduce the attack angle considerably. If possible remove any front and rear trim before hand to prevent it being lost while off road. Take your feet off the pedals and let the engine braking take you down the hill at a constant speed, keeping in a straight line.



Try to avoid travelling along a side slope. If you have to keep as low down the slope as possible and be prepared to carefully turn downhill at the first hint of a problem. Never try and turn up hill as this will shift the centre of gravity in such a way that you may roll over. If in doubt don’t do it.


Ditches and Mounds

Approach ditches or mounds at an angle to allow each wheel to tackle the obstacle individually, making the best use of the available ground clearance. If the obstacle is severe it can cause the vehicle to become cross-axled, with the diagonally opposite wheels coming clear of the ground - resulting in no drive.



It is rare that this would cause you to become stuck, but it can cause quite a shock as you come back into contact with the ground. This is one occasion where the axle differential locks come into their own as they put power to the two wheels that still have traction.




Mud and Ruts

Ruts deeper than the clearance under the vehicles axles will quickly have you stuck, so try to straddle them. If the ruts are shallow it is as easy to follow them. Avoid the temptation to fight the steering wheel or try and climb out of a rut. All this does is cause traction problems and damages the sides of the rut - and potentially your tyres. Always keep your thumbs clear to avoid injury if the wheel spins suddenly.



Deep mud is one of the few conditions when a little speed is called for. Build up speed gently before entering the mud and be prepared for sudden deceleration on contact. Stay in gear and take as straight a line as possible to firmer ground. Attempt to gauge the depth of the mud and be prepared for the worst. If in doubt, reverse before it’s too late. Often if you become stuck you will be able to get back out the way you went in if you catch it quickly enough. If on exiting the mud the tyres are clogged gently apply some throttle to clean the tread and restore traction.




Crossing Water

4x4 vehicles can frequently tackle water several feet deep, but always try to judge the firmness of the underlying surface before crossing. Water should never be driven through fast. A steady speed that creates a gentle bow wave is the best method in order to minimise drag and avoid flooding the engine. Always remember to drive a short distance with the footbrake lightly pressed on leaving the water in order to restore braking efficiency.



It is worth finding out where your engine air intake is located and how high up it is, as ultimately this will determine how deep you can go. In most cases it is alot lower than you think!



Also remember that water may well enter the cabin as they are not water tight. As modern 4x4's often have alot of electrical components inside the cabin water that is deeper than the door sills is best avoided.




Tyre Pressures Off Road

In most conditions the vehicle can be driven off-road at the same recommended tyre pressures as on tarmac. However in really muddy, low-traction conditions it can be beneficial to lower pressures to achieve better grip. This is because the tyre will deform due to the vehicel's weight - creating a bigger foot print on the ground. It is vital that extreme caution is used in these circumstances, as it is possible the tyre can detach from the rim if pressures are too low. Always re-inflate the tyres to the correct pressure immediately on returning to tarmac. Serious injury may result from a tyre coming off due to under inflation.