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What makes a good off-road vehicle?
Advice

What makes a good off-road vehicle?

Adventuring to some of the more remote parts of Australia typically requires a car that’s designed to do more than get you to the shops or the summer holiday house.

That’s where a proper off-road vehicle can make all the difference. But spotting one isn’t always easy.

While car makers have embraced the popularity of SUVs wholeheartedly, they’ve also done a good job of implanting the butch 4WD looks onto cars that aren’t designed to venture far beyond the bitumen.

And the badge isn’t always enough to tell the story. For example, until 2012 the Nissan Pathfinder was designed to go off-road, but the car that’s been sold since is then more about the city and suburbs.

So here’s a guide to some of the things to look for when shopping for a proper 4WD.

Ground clearance

The higher the car is above the earth below the less chance it has of scraping or getting stuck. Most four-wheel drives have more than 200mm of ground clearance, with some approaching 300mm. That compares with around 130-160mm for passenger cars and up to 200mm for many road-biased SUVs. Ground clearance has a big bearing on how far you can go without risking impacting the undercarriage.

Check the angles

Four-wheel drives open up a whole new book of jargon, including things such as approach and departure angles and rampover. They’re all important numbers that work with the ground clearance to help the car clear obstacles. As the name suggests, the approach angle denotes how steeply you can attack an obstacle.

The bigger the number the less chance you have of scraping the bumper. Similarly, the higher the departure angle, the less chance you have of snagging the rear bumper. Almost all 4WDs, though – especially utes – have a departure angle that’s lower than the approach angle. And if you’ve fitted a towbar that’ll likely reduce it more.

As for the rampover, if you imagine a pointy peak on the top of a hill, it references the angle of that peak you can drive over before scraping the underside. While ground clearance plays a big part here, so does wheelbase: the more distance you have between the front and rear wheels, the more likely the car is to catch its underside.

Wheel articulation

The ability for the wheels to move freely up and down within the wheel arches can make or break an off-roader. Most passenger cars and city-focused SUVs have minimal travel, or wheel articulation. That’s because they don’t need it; they need to soak up bumps and keep the car flat in corners and that’s about it. But with a four-wheel drive the suspension needs to work to keep the tyres in contact with whatever it is you’re trying to drive over.

Whether it’s a hole or log or rock, the ability for the suspension to mould around it and keep the tyres in contact with the surface gives the car more chances of finding traction, something a lot harder if wheels are hanging in the air. Traditionally that’s the reason hard core off-roaders have stuck with live axles (a beam connecting the left and right wheels), rather than the independent suspension systems common on road cars.

But many modern four-wheel drives use an independent front suspension system with a live rear axle, while others – including Land Rovers and Mitsubishi Pajeros – use independent suspension all around.

Protection underneath

All cars have some sort of protection underneath, but in most instances it’s plastic that is designed mostly to smooth the airflow to improve aerodynamics and reduce fuel use. Proper off-roaders protect key components such as the engine, transmission and fuel tank with more serious metal coverings. It means they can typically deflect a scrape or hit underneath, especially if it’s at low speed (most off-roading is done at slower speeds).

People who are very serious about their four-wheel driving may fit even stronger and more serious underbody protection. But at the very least you want metal protecting the critical components.

Tyres

Tyres are one of the most important parts of a four-wheel drive. And that starts with the spare. If the car you’re looking at doesn’t have a full-sized spare wheel then it’s probably not designed to do serious off-road work.

When in remote areas or rough tracks, tyre damage can occur quickly and unexpectedly, so it pays to have a spare that can keep you motoring. Most modern 4WDs have road-biased tyres designed to grip well in a range of conditions. Stepping up to a set of all-terrain tyres typically brings better puncture resistance and can aid with traction on gravel, mud, sand and more.

There will be compromises though, often relating to how noisy the tyres are or the grip they provide on the road. So weigh up the pros and cons. At the very least make sure the car you’re looking at has tyre pressure sensors. If it doesn’t, buy a set of aftermarket tyre pressure sensors so you can get an early warning of a slow leak. They can be invaluable in remote areas.

Dual-range transfer case

Hard core off-roaders will tell you a dual-range transfer case is what defines a proper 4WD. That’s not entirely true. A dual-range transfer case provides a separate set of gear ratios that make all the gears lower. So first gear, for example, will have the engine spinning much faster at 5 or 10km/h when low range is engaged. It’s designed to help with engine braking down a hill and allow slow speed crawling. It also makes it easier to get up very steep hills that may have been impossible for the engine if relying on regular gear ratios.

While most proper off-roaders have a dual-range transfer case – either selected via a second gear lever or, in newer models, a button or dial – it’s not mandatory for good off-road performance. Most Volkswagen Amaroks, for example, don’t have a dual-range transfer case, but they’re very capable 4WDs.

Locking differentials

Traction is king in a 4WD. And while car makers are increasingly turning to electronics such as traction control to adjust which wheels the engine sends torque to, it’s not perfect. For traction control to work, for example, it first needs to detect wheelspin, which in some instances could be enough to get you bogged. That’s where locking differentials come into play.

A differential is the thing that accounts for the difference in distance travelled between left and right wheels (AWDs and some 4WDs also have a centre differential to account for the difference in distance between front and rear wheels). Without a differential the car will be harder to manoeuvre and tyre wear is increased because the left and right are spinning at the same speed. But with a locked differential – or up to three locked diffs on a 4WD – the wheels can spin at exactly the same speed.

It means all four wheels have to be spinning before the car will stop moving. The added finesse of being able to feed on power without the wheelspin required to trigger traction control makes locking diffs very effective when traction is limited.

Recovery points

If you’re going to get into four-wheel driving, you’re going to get stuck – eventually. Sorry to be the bearer of bad news, but it will happen. That’s where recovery points come into play. Most proper four-wheel drives have at least one basic tow point front and rear to allow a car to be extricated from a bog. But check the load strength and rating of those recovery points, because for more serious 4WD recovery you’ll need rated tow points, which could mean bolting something on afterwards.

Snorkels and more

Most proper off-roaders are rated to drive through somewhere between 500mm and 900mm of water. Cars with a higher rating typically have their air intake under the bonnet positioned so that it is less likely to suck in water (something that can kill an engine). Or they could have a snorkel, which can raise the water fording depth even higher.

Make sure you know where your car’s air intake is and what it’s depth rating is. And don’t go being optimistic; if it’s 480mm deep and your car is rated at 500mm you need to be very, very careful and ensure you enter the water at the correct speed. Water crossings can be dangerous, especially if the water is moving.