Reality check on 4WD
I don’t take it personally, but despite spending most of my life testing cars, disappointingly few of my friends want my advice about which one they should buy. Many call thinking that they do, some even sincerely believe it, but in the past 20 years or so that I’ve earned my living this way, I reckon fewer than a dozen have actually bought a certain sort of car on my say-so alone.
I take this as a compliment. It means, I hope, that I have chosen to spend my time among people who know their own minds and therefore what is right for them rather better than me. So when they ring and appear to ask for a view, what’s actually happening is they’ve already decided what to buy and want me to validate that decision. If I don’t, it comes down to my professional opinion versus their gut feeling, in which case I don’t have a chance.
Which, I guess, is why so many of them insist on driving around the place in cars with four-wheel drive, from hulking great SUVs to small and compact family cars. My contemporaries and I are of an age where most of us have small children and we all know the instincts that drive us to do what we can to keep them safe. And, so the thinking goes, if you want to stay safe on the road, buy something with four-wheel drive because it will give you much more grip and therefore reduce the chance of you falling off the road.
Which would be a fine explanation were it not for the small but inconvenient truth that it’s almost complete rubbish.
I am an ardent supporter of primary safety in cars – that is a car’s ability to avoid having an accident in the first place – even if massively influential bodies like Euro NCAP appear not to be. When Max Mosley stepped down from its chair his stated reason was as follows: “The next big area of progress is the avoidance or mitigation of an accident before it happens. Getting this active safety right is a major challenge and will require more time from the chairman than I am now able to give.” That was four years ago. Since then has Euro NCAP announced so much as a single test of this most important aspect of car safety? It has not. In the meantime, cars have grown ever heavier as their manufacturers chase the secondary and passive safety targets set by Euro NCAP which are known to go down so well in the showroom.
If and when it finally gets around to it, it will be interesting to see how these four-wheel-drive cars fare, for while there is all the evidence in the world to put beyond any doubt the fact that measures like anti-lock braking and electronic stability control save lives, if there’s anything similar that applies to four-wheel-drive cars, I’ve not seen it.
On the contrary, and perhaps unfashionably, I think there’s every chance that out there in the real world beyond the science laboratory, four-wheel drive is as likely to get you into trouble as extricate you from it. Here’s why.
If, for the sake of simplicity you assume a 50:50 front to rear torque split, the advantages of four-wheel drive can be described as follows: it halves the traction requirement placed upon each tyre. And because lateral and longitudinal acceleration trade off each other, this means that you can apply more power nearer the lateral adhesion limit of the tyre before it will start to slip. So far so good.
The problem is that these advantages are only apparent if your foot is on the accelerator and, unless you are an unusually skilled or talented driver, the first thing you’re going to do at the first sign of trouble is take your foot off the accelerator – at which point your car becomes no-wheel drive like any other car on the road. And if, up until that point, you’ve been charging around in adverse conditions, revelling in all the extra momentum your four-wheel-drive system has allowed you to accrue, all you will have achieved is to raise the speed at which you finally fly off the road.
As you can see, what four-wheel drive does best is instil a false sense of security. Almost all of us will at some stage have accelerated away from a wet roundabout in a four-wheel-drive car and marvelled at how the car has stuck to the road. It gives you great confidence in poor road conditions which I am not sure is a good thing, particularly as while your traction may be better than that of an equivalent two-wheel-drive car, your brakes most certainly are not.
I’m guilty of it myself. I own a Land Rover so ancient I passed my test in it and on one occasion when seemingly snowed in, I decided to try and make it to the local village to buy some entirely unnecessary provisions. It felt fun, intrepid even, until I discovered ice under the snow and damn near turned the thing over. It didn’t keep me safe at all. What would have been safe would be having a two-wheel-drive vehicle, not even thinking of going out, and staying home by the fire.
Of course there are times when the purchase of an all-wheel-drive vehicle is eminently sensible. If you live down a muddy track, tow racing cars or work for the emergency services such cars more than justify their extra expense, mechanical complexity, fuel consumption and emissions. But for the rest of us it is perhaps worth just pausing before plunging and asking if the reality of four-wheel drive in any way matches its carefully marketed perception. And the answer to that, in almost all cases, is a loud and emphatic ‘no’.