What you need to know about Off-road vehicles
Four-wheel drive once meant rugged offroad vehicle. Now, a whole range of vehicles including sports cars feature four-wheel drive. Joe Kenwright tells you how to pick the real offroaders from the pretendersEven the experts are finding it hard these days to pick the genuine offroaders when so many straddle the fine line between butch highway cruiser and serious off-roader. Although you can no longer tell by looking at them, you can tell by what they can do and that's determined by what's under the skin.
What defines an offroader?
All rugged offroaders once had a separate chassis. Most still do but more are being built without a chassis. When they have to be heavily reinforced, these new chassis-less designs can be just as heavy as a separate chassis design. A genuine offroader is usually up to 200kg heavier than a light duty equivalent.
The presence of a chassis in most offroaders causes them to stand much taller than other vehicle types. However, the absence of a chassis allows the overall height to be dropped so there are exceptions. High ground clearance and skid plates protecting vital organs are still a reliable indicator.
- Wheels are usually taller with higher profile tyres than road vehicles.
- All should have dual range transmissions.
- Most have short or upswept front and rear overhangs with few parts hanging below the bumpers.
- Spare wheels are often mounted outside or inside above the floor out of harm's way and where they can increase clearance underneath.
- Critical water entry points such as the air intake, axle breathers, battery, power steering, alternator, starter motor, dipstick, master cylinders and key electricals such as engine computer should be mounted high and out of harm's way.
All offroad models once had the same simple part-time 4WD system that locked the front and back axles with a solid centre connection. Although more sophisticated systems are now commonplace, all genuine offroad vehicles should still have a centre diff lock function that replicates the original part-time system. - Serious offroaders once had beam axles front and rear for greater suspension articulation and constant ground clearance. Several of today's models have sophisticated independent suspension and self-levelling to replicate these advantages but they can be a compromise for constant heavy duty work.
Before you buy...
To steal a George Orwell phrase, some offroad vehicles are more equal than others. How quickly and safely they get you to your offroad activities and what they can do once you get there varies widely.
Spend less money and you will need to make a choice between a compromise for everyday running or a rugged offroader that can be a pain to live with on a day to day basis. For example, the differences between a Jeep Cherokee and a Toyota LandCruiser Troop Carrier highlight the extremes in the middle price range yet both can claim to be offroad vehicles.
As you spend more money, the manufacturers employ a bewildering range of technology to allow a vehicle to be an outstanding highway cruiser as well as an unstoppable offroader. Various Lexus and Range Rover models highlight how clever some of these all rounders can be. Buyers need to assess whether they want to be dependent on this level of technology in remote territory far away from specialist servicing.
The ability of an offroad vehicle is not just a product of its four wheel drive, extra ground clearance, drivetrain and ruggedness. The architecture of the body is critical. Long overhangs front and rear can affect a vehicle's ability to clear obstacles. A long nose will dig itself into a hill before the wheels can climb it. A long tail can suspend a vehicle and lift its rear wheels off the ground during a descent or climb. These abilities are measured in entry/approach and departure angles. The greater these angles, the better for offroad use.
The longer the wheelbase, the more likely the middle of the vehicle will end up suspended on a high point. The measure of a vehicle's ability to clear a hump is called ramp, breakover or crossover angle. Again, the greater the angle, the better for offroad.
All of these angles can be increased by simply raising the vehicle but this can generate stability issues and increase a tendency to roll. How offroad vehicle manufacturers achieve these angles while meeting other targets for passengers, luggage and handling explains the huge differences in these vehicles.
The serious offroad vehicles have relatively short wheelbases and short overhangs which can restrict cabin and luggage space. If the wheelbase is shortened too much, the overhangs will have to be increased to restore cabin space. Long wheelbase offroad vehicles usually have short overhangs but the ride height will need to be raised to achieve the same crossover ability as a short wheelbase equivalent.
Because it is so difficult to achieve optimum angles in all three measurements, the most expensive all-rounders are now featuring adjustable suspension to provide extra clearance on demand.
If you are thinking of buying an offroad vehicle for towing but never intend to go offroad, think again. Many serious offroad vehicles are already struggling to maintain reasonable performance and economy while carrying their own weight. Hitch a heavy caravan, boat or trailer up to some and there may not be enough grunt left for towing. Even if the engine will scream its lungs out as long as you are prepared to feed it fuel, it is the expensive transmissions that will fail if you get this equation wrong. A light commercial or local ute may do the job better.
When buying a used offroad vehicle, be aware that most buyers would have paid the extra when new for a heavy duty application of some kind. Checking the underbody, diffs and driveline is more important than for most other purchases. Because this is not always possible in an urban environment, it could be worth getting it checked by a repairer who specializes in this type of vehicle.
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