A Bentley Continental GT weighs almost the same as an Ariel, BAC, Caterham and Lotus put together. How have modern cars grown so heavy?

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.

I use the past tense because there are signs that it is starting to break free. Now that cars are taxed on CO2 emissions, the avoirdupois of modern cars is starting to hit the customer where it hurts and weights are slowly starting to come down. But the massive reductions that are required will come only when cars are taxed on their actual emissions, not those achieved in laboratories employing every single trick in a frankly bulging book of ways to make your emissions look better than they are.

 

The wheezes are plentiful and helped hugely by tests that bear no relation to how cars are actually driven. We all know about the illegal dodges thanks to the scandal that engulfed Volkswagen and implicated many others, but legal ones include making no-cost options out of equipment that should be standard (but can therefore be omitted from testing), making sure the tests are carried out on low-rolling-resistance tyres, matching gearshift strategies to the test protocols, having a default ‘eco’ engine map that drivers switch out of the moment they climb aboard and so on and on and on.

In the meantime, more progress is being made by some than others in the quest to shift the flab, although before we start handing out prizes, it should be said that these tend to be the manufacturers most needing to progress. The entry-level version of the previous Land Rover Discovery weighed 2570kg, the new one just 2105kg, despite offering only a fraction less power and, of course, a wildly improved power-to-weight ratio. That’s a 465kg saving and there are entire cars out there that weigh less than that.

But there are no shortcuts to reducing weight and the process costs money that is very hard to recoup from the customer: it’s very easy to sell the value of an additional 100bhp, very hard to sell the subtraction of 100kg. Which, of course, is why manufacturers have to be threatened at legislative gunpoint before they’ll make the changes required.

Those changes involve using not just less material, but also different material. Much of the weight reduction achieved by Land Rover has come from using aluminium instead of steel for its structures. But aluminium is more expensive to buy and use in production, exotic materials like carbonfibre even more so. So manufacturers must also be forced to think more laterally, like Chapman all those years ago, and get clever in ways never required before.

Ultimately, however, weights will only start to tumble across the board if it is what the customer wants. And what will bring about that change in attitude? Education and incentive. If it becomes understood that lighter cars are inherently better cars and can be safer, too, and if cars become taxed on their real-world emissions, then weight will start to fall – and fall fast. And just as heavy cars got heavier because of all that was required to support their heft, so light cars can get lighter, a circle not vicious but virtuous. The result will be cars not just more frugal, but more fun, too, and to the benefit of everyone from the most diehard petrolhead to the most ardent environmentalist. Such changes cannot come soon enough.

Read more

Lightweight car tech: do car makers mean lighter, or just less heavy?

2017 Lotus Elise launched with new lightweight Sprint edition

Our Verdict

Bentley Continental GT

Full of character and still able to impress, particularly as a V8

Join the debate

Comments
23

8 July 2017
Good article, next you could do one about the virtues of reducing unsprung weight - few people seem to know about this. Carbon fibre is the future, does anyone know why its STILL so expensive - its only strands of carbon (which is plentiful) covered in resin (which is cheap), its been around for years, I think the price is being kept artificially high. Dont agree about the whole real world emissions/economy testing thing, I cant see any way that you can test cars outside in the real world on equal terms, well not until we find a way to control the weather and of making EVERY driver in the world drive exactly the same way at all times. The solution is for authorities to do ALL the testing and for consumers to be informed that the figures are guidelines only.

9 July 2017
The issues that make carbon fibre expensive are:
a) long cure time for the resin - means you need a larger factory whilst it cures
b) high labour intensity for laying up complex shapes
c) Variable quality as "hand made"

All of which can almost certainly be overcome/improved a lot with investment in manufacturing process and methods but so far the "cost of weight" hasn't been high enough to justify such research - however it is now happening with the premium germans (especially BMW) leading the way

8 July 2017
I totally agree with typos1 that real world testing is a waste of time and effort - what's needed is a more demanding lab test that's more in line with most peoples' car usage. Hopefully the upcoming World Light Duty Test Cycle (WLTC) will address this.
Regarding why cars have become so heavy, well it's because people want cars which are refined, well equipped, safe and above all cheap. Fuel continues to be very cheap (in relative terms) and the focus on CO2 has resulted in a shift to diesel rather than lighter more efficient petrol cars. Performance and driving dynamics just aren't important for most people. It might help if magazines like Autocar placed more emphasis on car weight in tests and features, using actual test data rather than manufacturer's own figures (which can be manipulated for homologation purposes).

8 July 2017
How hard can it be for road testers to record actual fuel consumption and, in the case of the long term tests, give an indication of the type of use? They should all do it. If you want to be really accurate, check the odometer against mile posts and make any adjustments for manufacturer's built in "optimism" and measure fuel by the brim to brim method. Also find a place where you can weigh them in road ready condition; Lamborraris are famous for being weighed practically on the moon.

8 July 2017
To start with it's not that easy to brim a modern car, since tanks have an expansion space designed to prevent brimming (so preventing fuel loss during a hot day when the tank is full and the car not used). Ideally then, you should fill the tank at the same fuel pump with the car in the same position and stop when the pump clicks off. OK I'm being fussy but unless such procedures are followed it would need around 1000 miles travelling to minimise such errors. Then, ideally the measurements would need a temperature correction, since fuel consumption improves about 1% for every 3deg C increase (so almost a 10% difference between summer and winter). And you're right about odometer correction. I can recall a certain French car whose distance recorder over read by 6%, so "perceived" consumption would have been better than the actual figure by this same amount. Who said that cheating was new?

8 July 2017
saying "it's just" doesn't make it easy or cheap to produce! other things must be taken in to account too, such as repairability after a crash, resistance to minor impact damage such as grouding it out a bit or some decent stone chips; steel/aluminium are ductile and tolerant, cf is brittle and gets annoyed by such things. then there's fatigue, which steel isn't too bothered about but cf is. fire resistance. the list of issues goes on.

if the manufacturers were actually interested in making things notably lighter, why would they continue to think of things to weigh them down with?

8 July 2017
saying "it's just" doesn't make it easy or cheap to produce! other things must be taken in to account too, such as repairability after a crash, resistance to minor impact damage such as grouding it out a bit or some decent stone chips; steel/aluminium are ductile and tolerant, cf is brittle and gets annoyed by such things. then there's fatigue, which steel isn't too bothered about but cf is. fire resistance. the list of issues goes on.

if the manufacturers were actually interested in making things notably lighter, why would they continue to think of things to weigh them down with?

8 July 2017
can this quirk of the website be sorted out please?

8 July 2017
Suzuki has the most success in reducing weight on their mass produced cars. Mazda is trying very hard but their cars are not as light yet.

10 July 2017
Yes the latest hybrid Suzuki Swift Boosterjet is under 900kgs

Pages

Add your comment

Log in or register to post comments

Find an Autocar car review

Driven this week

  • Porsche Panamera Turbo S E-Hybrid
    First Drive
    25 July 2017
    New top-of-the-line Porsche hybrid, though fast and flexible, is simply too heavy to strike the same sweet sporting compromise as its siblings
  • Caterham Seven 420R Donington Edition
    First Drive
    25 July 2017
    Limited-edition road-legal Caterham track car is a superbly enthralling drive, with enough creature comforts to be used on the road as well. Even more addictive than most of its rangemates
  • McLaren 570S Spider
    First Drive
    25 July 2017
    McLaren has created its most attainable drop-top by removing the roof from the 570S coupé, but none of the car's talent has come away with it
  • 2017 Range Rover Velar
    First Drive
    23 July 2017
    The Range Rover Velar is the most road-biased car Land Rover has made. So does it still feel like a proper part of the family?
  • Seat Ibiza
    Car review
    21 July 2017
    A model upon which Seat has staked its future, the new Ibiza must now deliver