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4WD: A deflating experience
Appropriate skills and technique are required to negotiate power sapping soft sand. Picture: Copyright GBTW

Experienced motorists know sand driving requires skill and correct application of fundamental rules of flotation and momentum.

Simply put, if you adjust your tyre pressures you can aid the flotation of your vehicle across the sand. Add sufficient speed to maintain forward motion and you minimise gravity's ability to pull you down into the soft stuff.

No, your two-tonne vehicle doesn't become lighter, nor will it tread water - unless you're Jeremy Clarkson and wasting someone else's money creating a Toyota.

What I'm referring to is the effect from increasing surface area in contact with the ground. Most people can recognise a flat tyre - reduced pressure collapses the sidewalls outwards, making the tyre appear fatter.

But bulging sidewalls do very little, regardless of whether tyres are skinny or "fatties". What is far more important is that lower tyre pressure gets more tread in contact with the ground by lengthening the tyre's footprint.

The result is better distribution of the vehicle's weight over a larger surface; just like an Eskimo wearing snow shoes, rather than sinking through the snow on a pogo stick.

Check for yourself - place a piece of dowelling in front of a fully inflated tyre where it meets the ground and one at the back. Measure the distance between the sticks. Deflate your tyre and repeat the process. As a rough indication, the footprint of a tyre at 15psi is about twice as long as one at 50psi.

How low should you go? It depends on the vehicle, tyres and rims, load being carried and softness of sand. Your local 4x4 specialist is a great source of knowledge based on practical experience. Both Coopers and Mickey Thomson produce a glovebox guide to tyre pressures for various terrains.

Before you plunge into sand, always deflate your tyres to an appropriate pressure for the conditions. As a general guide the "right" pressure is between 16 and 22psi, because sand compaction can vary immensely from near- solid road base to powder.

Too low will risk rolling a tyre clean off a rim; worse than being bogged. But if the alternative is to abandon the vehicle to the incoming tide, deflating tyres to 8psi is worth the risk.

The speed required to maintain momentum also varies. Smashing through dunes is environmentally irresponsible and your passengers may send you their physio bills.

Too slow and you'll spend more time digging than driving.

Maintaining the right amount of momentum is key to successfully negotiating softer conditions, but the rule of thumb is - as slow as possible for control but as fast as necessary to maintain forward motion.

Take off and accelerate smoothly to where you feel comfortably in control.

If you feel yourself starting to sink then don't jab the pedal to the metal because your wheels will dig in and down you'll go. Instead, smoothly increase the pressure on the throttle to keep up momentum.

Before heading into the sand, check beach conditions and tide movements with a ranger or experienced local. Pick your path intelligently on the beach.

There is an element of art to sand driving. Even the best, applying both scientific principles and experience, still get stuck in the sand sometimes.