Preparing well avoids 4WD misadventure

01-10-2008 | Tim McVeagh

Some people have the luxury of planning their first off-road driving experience while others are thrown in the deep end due to conditions or circumstances beyond their control.

. Planning a trip allows time for the vehicle to be prepared, a buddy vehicle organised and allows the driver to choose suitable weather conditions and terrain.

For those thrown in the deep-end, any vehicle preparation will be a bonus. Beyond that, drivers will have to rely on common sense and any previous experience.

Whether the introduction to off-road driving is planned or forced, some background knowledge will help equip the novice driver for what may lie ahead.

Firstly get to know the vehicle.

Four wheel drives (4WD) may be anything from a basic "mule" still in farm service, to a much more complex SUV. Either way, instruction from someone who knows the vehicle will flatten the learning curve.

Many of the traction and braking devices on modern 4WDs operate automatically and need no specific input from the driver.

But other vehicles may have equipment that is manually operated by the driver to reduce the risk of becoming stuck.

Free-wheeling hubs allow the front wheels to "free wheel" when in two-wheel-drive, which reduces tyre wear, fuel consumption and mechanical wear. The hubs must be engaged for 4WD. In some vehicles this is done automatically by selecting 4WD.

In more basic vehicles the free-wheeling hubs need to be engaged manually at each of the front wheels. To engage them, rotate the hubs from "4x2" to "4x4".

Centre diff locks on full-time 4WDs engage the front and rear axles. These must be used where traction is limited to maximise off road capability.

Manually operated diff locks for individual axles will lock both wheels of an axle to help negotiate particularly slippery terrain.

Knowing when and how to use these features will reduce the chance of becoming stuck when the going gets rough.

In addition to the usual vehicle emergency equipment, to prepare the vehicle for off-road conditions include a tow strop.

A purpose-made snatch-strap makes vehicle recovery more effective and reduces the stresses inflicted by a less elastic tow-line. Chains and wire ropes are not suitable for vehicle recovery.

Suitable shackles can be bought from a 4WD specialist, as some shackles can break and become lethal missiles.

Most off-road drivers will get stuck at some stage. If you are the sole vehicle, then shovels, jack, and winches may get you out. If you are with other vehicles, then towing is a common option, but one fraught with danger for the unwary.

Use tow hooks for vehicle recovery, not tow balls. Tow balls can break and catapult at high speed in the direction of the other vehicle.

Most importantly, make sure everyone is well clear of the stuck and recovery vehicles and the winch and tow ropes between them.

Also include a shovel or spade in the vehicle kit, as digging may be the only way to release a stuck vehicle. A high-lift jack will allow a bogged vehicle to be raised. Take a tyre pump if tyres are to be let down to increase traction.

Before setting off tell someone where you are going and your estimated arrival time. Make a phone call, text message, email or leave a note, but let someone know where you are going. These few minutes could reduce search time by crucial hours, if the worst happens.

Reducing tyre pressure increases traction, particularly in mud. 140kPa; (20psi), is a safe pressure for less serious off-road driving.

The tyres should be re-inflated to their usual road pressure when heading back onto road surfaces.

Engage 4WD, or lock the centre differential in a full-time 4WD before the going gets tough.

Four-wheel drive allows better traction, steering and braking. Change back when driving on hard surfaces to reduce tyre and mechanical wear.

Engage low ratio for slower going. Lower gears are needed for more challenging tracks. Running in a higher gear in low ratio also means that first gear/high ratio is not getting a hiding.

Steer the vehicle in rough terrain with thumbs outside the steering wheel to avoid injury in the event one of the front wheels hits a solid object such as a boulder or stump. The steering wheel can rotate suddenly and very quickly.

Different terrain and surfaces such as sand, mud and steep hills require different driving techniques.

"Time and tide will wait for no-one", so getting stuck on a beach can have dire consequences for the adventurous but inexperienced 4WD owner.

Drive in hard sand where possible as it takes less effort to drive over and at best can be quite similar to driving on a road.

Constant progress is better than stopping and starting, as wheels are more likely to dig in when starting off. When driving up or down sand hills, drive straight up, or straight down to reduce the risk of rolling.

Check the tides on beaches and estuaries before setting off.

Rumour has it that many years ago one new car never made it home from the show room to a Wairarapa sheep station only accessible by beach, when the owner was caught by the incoming tide!

And remember that beaches are classified as roads and all road rules apply.

Mud is a fact of life for most NZ farmers through winter, but also provides hours of entertainment for the recreational four-wheel driver.

Getting stuck may not have the same consequences as getting stuck on a beach, but can be equally frustrating.

Steering is less positive in muddy conditions, especially on side slopes and hills, so be prepared for the vehicle to slip and slide and be conscious of where it could slide to. Keep the vehicle moving to reduce the risk of bogging.

Momentum, (a product of weight and speed), is often an important factor in getting through a difficult section of the route.

Soft mud surfaces may be over a hard base, or over more soft mud. So wheel spinning will dig you down to get traction on the hard base underneath, or alternatively dig you deeper into the mire.

Wheel spinning is loss of traction so should only be used as a technique to dig down to a firm base.

Use a higher gear at lower revs, rather than a lower gear at higher revs, to reduce the chance of breaking traction, (wheel spinning).

Stay in wheel ruts if the ruts go where you want to go and they are not too deep. Deep snow should be avoided if at all possible.

When driving in snow follow in the tracks of previous vehicles, as they have already compacted the snow and this allows more positive traction.

Chains will increase traction significantly in snow, so fit them off the road in a safe place.

Low gear should be used for going downhill and only use brakes when necessary.

And remember that snow can build up under the bonnet. This may affect electrical gear and freeze up around steering equipment, so keep the mechanicals free of snow.

There is a risk of rolling a vehicle when driving across a slope. This can happen unexpectedly when, for example, a downhill wheel drops into a hole.

To minimize risk use a low gear and drive slowly. Avoid dips and holes on the downhill side of the vehicle, as these can suddenly increase the tilt of the vehicle.

Look out for alkathene pipes in paddocks, which can cause the vehicle to suddenly slip sideways. And most importantly, if the vehicle becomes unstable, turn downhill as quickly as possible.

To reach the top of a steep hill without incident, select a suitable gear before starting to climb the steep bits, as changing gear on a steep slope may mean coming to a stop.

It's a lot harder to get going than to keep going on a steep slope. If the gear you pick is too high, then the vehicle may easily stall; if it is too low, then you may wheel-spin, or not be able to gather enough speed.

Drive straight up the hill where possible rather than across and up, where rolling the vehicle is more likely.

Failure to make it up a steep incline may be due to loss of traction wheel spinning), or stalling the engine.

Wheel spinning is more likely on soft ground. Let the wheels spin a little to dig in, which will stop the vehicle from sliding back down the hill.

If you power on, you may make further progress up the hill, or you may lose control as the vehicle slews around.

Best to "dig in", then turn the engine off, without touching the clutch and put the foot brakes on.

This will hold the vehicle in place while you gather your thoughts. After making sure the reverse path is clear of vehicles and people, put the vehicle into reverse gear, while still holding with the brakes.

Turn the front wheels to the correct position then release the brakes and start the engine at the same time, - no clutch and no accelerator.

Use brakes only when necessary to slow the engine down. This procedure should be practised on a gentle slope.

Where the vehicle has stalled, the procedure is the same, although an attempt may first be made to start up the slope in a lower gear.

Driving down steep hills can be the most dangerous aspect of off-road driving, as vehicles can often get away on drivers.

Use low ratio, and a low gear. If the gear selected is too high, then the vehicle will tend to run away.

If the gear selected is too low, then the vehicle will tend to break traction and slide. Drive straight down the hill rather than across it and wherever possible follow wheel ruts.

Use brakes only when necessary, braking lightly to avoid locking up the wheels.

Water crossings can be dangerous and should only be attempted if there is no alternative, and only after careful consideration.

The depth, flow, and firmness of the riverbed or bottom should be assessed. Even heavy SUVs can be swept away by a moderate current. In a river, this may mean being swept into deeper, more turbulent, or more dangerous water.

The safest place to cross a river will be at the top of a rapid, as this will be the shallowest.

Use a low gear in low ratio, creating a small bow wave, which will keep the engine relatively dry.

Avoid changing gears while wading, as this can let water into the clutch mechanism.

Where the riverbed is loose, a vehicle will readily dig itself down and "belly" if it is allowed to wheelspin.

So if you stop making forward progress, stop and try to back out.

After coming out of the water pump the brakes when under way, to dry them out.

Four Wheel Drive Clubs offer advice and assistance to novice drivers, safety in numbers, access to private and restricted land, social and serious competition and companionship with others of a common interest.

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