SUVs are sophisticated off-road vehicles that utilise technologically advanced four-wheel drive systems. So before you buy one, consider whether you need that expensive technology.
On the plus side, four-wheel drive vehicles are safer as they split power between the axles, giving enhanced straight-line tracking and extra agility through corners. When slip is detected, a four-wheel drive vehicle's centre differential distributes torque to the axle with the most grip. This means reduced understeer or oversteer and improved grip in situations where a two-wheel drive car would be sliding.
This is how Audi took the rally world by storm when it introduced its Quattro 4x4 cars onto the circuit in 1981. Audi has continued to develop its Quattro technology and offers it on cars like its impressive All-Road A6-based estate car. Along with Audi, Subaru has a tradition of all-wheel drive and offers 4x4 in cars like the Impreza. So, if it's the safety of improved traction you're after, you can get the benefits without buying a large SUV.
But 4x4 vehicles, while offering greater safety are more expensive to buy, service and run as more fuel is needed to drive all four wheels.
Four-wheel drive SUVs come into their own when towing, but consider first where you will be travelling. If you are going from caravan site to caravan site, a diesel-powered car may be more suitable. Diesels benefit from increased torque at lower engine revolutions meaning the engine is more able to cope with the extra demands of towing.
In addition, cars are more stable than SUVs, which are high-sided and generally have a higher centre of gravity. This means that while they offer improved visibility, they are less stable, especially when swerving at speed.
However, for those towing horseboxes or speedboats there is often the need for four-wheel drive, especially in wet fields or sandy beaches. In this case, a 4x4 SUV is the ideal choice. Ensure first that the SUV has the ability to power all four wheels. It may seem obvious but an increasing number of so-called soft roaders, such as the Nissan X-Trail, are available with just front-wheel drive.
There are two types of 4x4s: part-timers that switch between two and four-wheel drive, and permanent four-wheel drives that continually power front and rear axles. If you spend most time on the road, a part-time 4x4 is the obvious choice because of its lower running costs.
If towing, look for SUVs that provide an automatic holding for hill starts. Subaru's hill-holder clutch has proved especially popular as it prevents rolling backwards when pulling away on a gradient. Also if you intend to do a lot of towing, look for SUVs that have self-levelling suspension systems, which maintain a constant ground clearance even when the vehicle is fully laden with passengers and luggage.
For towers and serious off-roaders, a dual-range gearbox may be required. On manual five-speed vehicles, a dual-range gearbox essentially turns the vehicle into a 10-speed model - five high-range gears for normal use and five low-range for situations where extra engine control is needed for crawl climbing or when pulling a caravan off a rain-soaked field.
Most SUVs use viscous coupling or electronic limited slip differentials and electronic braking systems to ensure power only goes to the wheel or wheels with traction. For serious off roading, one should go for a vehicle that has a differential lock so that power can be sent to, for example, both rear wheels, regardless of whether they both have traction, which is important when tackling deep snow or mud.
There is a trend towards using sophisticated electronics to determine the optimum off-road vehicle set up. The Land Rover Discovery 3 with its terrain select system, for example, allows the driver to select one of five terrain settings from a centre mounted dial. Simply select the condition that matches your off-road route and the electronics will set up vehicle, suspension, engine and throttle settings.
Hill descent is also standard on most SUVs. These systems use engine braking and ABS to prevent wheel lock and vehicle runaway when tackling steep downhill off-road gradients. A superb system, but are you really going to need it?
If you're in the market for an SUV, buy with your head and not your heart. Otherwise, you may be paying for costly but redundant technology.