Why do large four-wheel drive (4WD) cars, which presumably do more rough road and off-road motoring, last so much longer or better than street cars which are used almost entirely on tarmac? Mr Average
4WD workhorses have to be built stronger (in several ways) to do what they are designed and intended to do. And because they are purpose built for their “heavy duty” task, they are less stressed by it.
The conditions they operate in may be severe, but they are mostly well within the vehicle’s capacity. Driving up a steep and boulder-strewn track is like...popping down to the shops.
Street cars are also built for their intended conditions and tasks, but our roads and “ordinary motoring” conditions require them to operate much nearer and sometimes beyond the limit of their design (which is compromised by weight-saving for performance, running economy and price).
That is one reason big 4WDs are likely to last longer – though case-by-case durability of any type of vehicle also depends on the quality of design, materials and manufacture, the diligence of maintenance, driving style, type of use, and the external conditions of operation (what loads they carry, what roads they use). But there is more...
All mass-production cars are designed to be multi-purpose. The majority of customers want them to seat several passengers, carry some luggage, handle safely, ride comfortably, be adequately swift, accelerate brightly, cruise at good speed on highways, cope with some imperfect surfaces, be manoeuverable, fuel efficient, reliable, durable, fixable, and so on.
That’s the baseline of what they all are expected to do, and what designers and manufacturers provide...in different shapes and sizes, to differing styles, different degrees and at different prices to cater for a range of preferences and lifestyles. In that respect, the highest number of customers occupy a broad “middle” ground.
And that middle ground recently got a whole lot bigger with the development of the SUV - more versatile than a street car, less specialised than a go-anywhere 4WD. And SUVs are very evidently the latest and fastest-growing bestsellers. Most are not (!) toughened workhorses.
But there is still room and demand for more specialised designs, with more extreme purpose-built capability: more sporty or more muscular, more economical or more powerful, smaller or bigger, simpler and cheaper or more opulent and indulgent. Slightly, moderately or extremely...in one direction or the other.
The challenge is that when you make one aspect of a car’s character “better” the laws of physics tend to make another aspect “worse”. A car that is stronger will be heavier. A car that is powerful will consume more fuel. And so on. There is technology to avoid that, but then something else has to change: the price.
There are vehicles which go both ways...to an extreme. They can do 200 kph down a highway and (!) drive off-road up the side of a mountain. There are such cars are in our showrooms...but in Kenya, cars that can do that cost as much as building a bespoke three-bedroom house, complete with executive furniture and fittings!
There is a x 20 difference between the price of the cheapest new car that ticks just enough boxes to find a buyer, and top-of-the-range mass-produced do-it-all King of the Road. That’s what it takes to avoid the “worse” effects of making everything “better”.
4WD workhorses are not in that super league, but they are at the muscular end of the multi-purpose spectrum. Dig a little deeper and you will find most big 4WDs have diesel engines, which are lower-revving than the petrol engines of their street-car cousins.
That means they have less horsepower (for acceleration) but more torque power for hard pulling or climbing. They don’t have to charge at obstacles and take a thumping; they pick their way across terrain like chameleons. Gently. And with a low-range transfer box and grip shared between all four wheels, their transmissions give their engines an easier task.
Because they do a higher proportion of their work in remote areas, they tend to be checked and serviced more diligently, and – to ensure reliability in the wild - faulty parts are more likely to be replaced than fudged fixed.
They tend to have bigger wheels and higher-profile tyres that cushion them better on rough surfaces, they have longer suspension travel and double-strength springs and dampers, they have steel girder chassis (not a moncoque shell), their body panels are thicker, and all the linkages are significantly fatter and more robust.
In fashion terms, 4WDs are denim and leather. Street cars are cotton and silk. So, pick the cloth that suits your purpose. And expect one to last a lot longer than the other.
