Insight: why the weight of your car is so important

Magic wands don’t exist, at least not outside Hogwarts. Progress has to be fought for and won. This is especially true in the field of automotive engineering.

But what if there was one thing you could do that just made everything better for cars – one act that instantly conferred superior acceleration, higher cornering speeds, better handling, improved braking, lower fuel consumption and fewer emissions of every single kind? And what if, as it did so, it also used far less of the world’s finite natural resources? Would that not be as close to a wand fit for a wizard as can exist? Well, it does exist and it has been known about for as long as people have been making cars. It can be defined in three simple words: make it lighter.

Lotus founder Colin Chapman was by no means the first to understand the concept, but he pursued it with greater vigour than anyone up until that time. His maxims such as ‘Simplify, then add lightness’ and ‘Adding power makes you faster on the straights; subtracting weight makes you faster everywhere’ are among the most famous in our business. He didn’t just use fewer and thinner materials, but he also used them cleverly, understanding, for instance, that single components could be made to multi-task, such as using driveshafts as suspension links. And now, as then, the principle is sound: a 376bhp BMW X5 M50d and a 134bhp Lotus Elise Sprint have quite similar power-to-weight ratios, but I know which I’d rather drive.

Which is why, one day, someone will sit down and write a book about why and how it all went so horribly wrong – how the mass of cars grew so much that over 20 years some had ballooned to weigh almost half as much again as their forebears.

As I see it, there were essentially three reasons. Most obviously, people wanted more content in their cars, whether it was designedin luxury such as thicker seats or additional soundproofing, or addedon gadgetry like higher-specification entertainment. The scales don’t discriminate: it all adds weight.

Second, car manufacturers suddenly discovered they couldn’t sell their cars unless they scored highly in crash tests, so they started designing them specifically to pass these tests. Oddly enough, I don’t remember any communication of the fact that the weight added by this process made them more likely to have the crash in the first  place. In medicine, prevention trumps cure every time. In marketing, it barely gets a second glance.

The third reason is a consequence of the first two, because once you’ve built your car to be comfortable, luxurious and safe (at least when it crashes), you discover that it has become rather heavy and, therefore, rather slow, and the customer won’t like that. So do you reduce the weight? Of course not, because it is far, far cheaper simply to add power. But if you add power to a car that’s already heavy, it becomes heavier still because it’ll probably need a bigger engine, and certainly beefed-up suspension, wheels, tyres and brakes. And that, right there, is the vicious circle within whose perimeter the industry lived for far too long.