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4WD DRIVING SKILLS

SNOW DRIVING

The white stuff is pretty, but it can be scary, too

Snow driving falls into two categories: getting to the snowfields on plough-patrolled bitumen roads; and dirt road and trail driving. Both pursuits have their hazards.

snow drivingDriving a well-maintained 4WD on patrolled roads above the snow line shouldn't be a hazardous occupation, if you follow some simple procedures. 'Take it easy' is the overriding rule.

We know it's expensive going skiing and to get your money's worth you want to power into the powder as soon as you can, but once there's snow, slush and black ice around it's time to get off the loud pedal and plan every manoeuvre carefully.

Minimise braking and avoid sharp acceleration, because even a traction and stability controlled 4WD can get out of shape if its tyres can't grip properly.

Black ice is the principal hazard on bitumen roads. Black ice forms after sun-melted snow flows across a road and freezes when the temperature drops overnight. It's called 'black' because it looks like a flow of melted bitumen.

Black ice has about the same co-efficient of friction as glass, so when your tyres run across it they have no grip at all and you're temporarily out of control, regardless of stabiity control (ESC), traction control (TC) or any other traction aids you have on board. Thankfully, most such ice patches are short, but sometimes they're long enough to send vehicles into the shrubbery or worse.

Black ice is an obvious night hazard, but is a daytime risk on shady stretches of road that haven't had any warming, melting sun.

black iceOn plough-patrolled roads be very careful where you park your 4WD. Don’t stop in positions where your vehicle can be struck by an out of control machine.

Also, don’t park on the road edge where snow ploughs are likely to be working, because if your vehicle is buried by a heavy snow fall the plough driver won’t be able to see it. Plough blades are uncompromising.

Don't turn the heater up full blast and strip down to a T-shirt when you're snow driving. If you have to get out of the car you'll get cold as you scramble into winter-weights and maybe fall over as you hop around trying to pull on your boots.

It's a better proposition to have mild heating inside the 4WD and keep your boots and woollies on. That way, if you have to get out it's only a matter of pulling on a hat, gloves and a parka and you're comfy.

Also, in the event of an accident that stalls the engine and renders you unconscious, hopefully you won't freeze to death before someone finds you.

Dirt road and trail driving above the snow line is usually limited by road closures, but some private roads remain open.

Never drive on closed roads: firstly, because they've been closed for a good reason and, secondly, no-one will look for you there, if you become stuck and your tracks are blanketed by fresh snow.

In good weather conditions unsealed surfaces provide less tyre traction than bitumen roads, but have even less grip when they’re snow or ice covered. Any climb or descent is fraught with danger.

You should judge carefully the need for off-road driving in the snow.

 

Chains and snow tyres

In Europe and the USA many people fit snow tyres for the winter. In far-northern zones these tyres are often fitted with steel studs, to enhance grip.

Proper snow tyres are very rarely seen in Australia, because they're designed with very soft rubber tread compounds that are for use in constant low temperatures. They also have multiple sipes (small cuts) in the tread pattern. These tyres aren't suitable for use in moderate and high ambient temperatures, because they will tear and wear out very quickly.

The most common snow tyre compound and pattern seen in Australia is 'M&S' - mud and snow - which is a compromise tyre that can be used at higher speeds, on gravel roads and in higher temperatures.

Regulations in Victoria and Tasmania require all vehicles to carry tyre chains in snow-affected areas. Mount Hotham in Victoria even specifies that these chains must be diamond-pattern, despite the fact that many new vehicles don't have clearance between tyres and suspension components to fit them.

In NSW, 4WDs do not have to carry chains. However, we reckon you should have chains for any vehicle travelling into snow areas.

You need to check your owners' manual to find out what type of chains can be fitted to your 4WD and if you need to fit four, not just two.

The advantages of chains are clearly shown in the following European traction and braking tests.

A traction and braking test performed by chain-maker, Pewag Austria, demonstrates how important tyre chains are when snow and ice cover the roadways. New snow tyre technology has improved performance dramatically, but, as OTA's own testing has confirmed, when it comes to maximum grip nothing comes close to good tyre chains.

 

Traction and climbing ability

Conditions: hard packed snow, -5C, slope 22 degrees.

A - Tyre chains on all four wheels; B - Chains on one axle; C - Studded snow tyres; D - Snow tyres.

Snow tyres managed 27 metres before spin-out occurred. Studded snow tires managed a two-metre increase. Snow tyres with one pair of tyre chains saw the vehicle reach the 32.5-metre mark. A dramatic increase in traction occurred with two pairs of tyre chains: 60 metres, or almost twice as far as with one pair of chains.

 

Braking and stopping distance

Conditions: hard packed snow, -5C, speed 25km/h.

A - Chains on all four wheels; B - Chains on one axle; C - Studded snow tyres; D - Snow tyres.

The best stopping distance in this test was 5.5 metres, with tyre chains on all four wheels. With chains on only one axle the stopping distance was almost twice as long, at nine metres. Snow tyres, studded or not, needed a 12-metre stopping distance.

 

Vehicle Preparation

If you're heading for the snow you need tyres with better than one-third original tread depth. Barely legal ones that just pass the match-head depth gauge test are best kept for next summer's beach forays.

Don’t have warm-climate diesel in your tank, because it’s likely to plug your filter with wax crystals. Fill up with winter-grade fuel near the snow fields – it’ll be more expensive than city fuel, but it’s formulated to reduce waxing.

snow drivingIt may seem odd to be worried about your cooling system when you're headed for the snow line, but water occupies its maximum volume just before it freezes. This expansion is powerful enough to crack engine blocks and cylinder heads.

The cure for frozen cooling systems is the correct coolant mixture specified by the engine maker. However, coolant mixes have finite lives and some types lose their anti-freeze properties in year or so. You may need to have the system drained and replenished before winter sets in.

Some vehicle makers specify a different oil grade for winter and summer, but this is usually intended for vehicles that are stationed through the entire winter in cold regions. It's unlikely your vehicle needs a different oil grade for occasional visits above the snow line during winter. It's the same situation with transmission oils.

Oil won't freeze in Australian winter temperatures, but it does become sluggish. An oil change before heading to the alps means that your oil isn't full of contaminants and will flow more freely when cold. Anything you can do to lessen the chill factor - parking under cover, for example - will help.

If you're spending a lot of time in freezing conditions you can make your engine's life easier by using a heater - either the type that warms from under the sump, or one that fits into the cooling system or slides down the dipstick hole.

snow lightingMotorist assistance organisations are always busy in winter with vehicles that won't start. Cold weather often sounds the death knell for aged batteries and wet conditions test faulty connections.

You don't need a dud battery or dodgy electricals in the snow, because it's not just inconvenient when your 4WD won’t start - it may be life-threatening. Any battery that's three or more years old is suspect.

Electrical connectors and wiring looms, from the battery posts right through to the tail lights, are worth a check, before you venture into the icy bush.

Lights are vital, for seeing and being seen, in foggy conditions. Make sure yours are functioning properly and that you have spare globes on board.

 

 



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