Over the years there has been a creeping, unnoticed, pervasive shift in a critical aspect of cars. It's an evil that harms performance, worsens fuel economy, and has a negative affect on braking and cornering. Car companies spend millions of dollars trying to keep it under control, but each year it seems to escape the hatchet a little bit more.
And what are we talking about? Vehicle weights, that's what.
Heavier and Heavier
Do you realise, for instance, that the weight of the just-released Subaru WRX STi is about the same as that of an HZ GTS V8 Holden from 1978? Don't believe us? Well, the Holden was quoted as 1475kg, and Subaru suggest that the STi weighs-in at 1470kg!
So yes, that full-size Holden from yesteryear is within a bee's dick of the weight of the 'little' pocket rocket. But hey, how different are their dimensions, anyway? The Holden was 4844mm long, the STi is 4405 - that's 439mm (17 inches) difference in length. Width? Well, the Holden was 1877mm wide, while the STi is 1730mm, a difference of 147mm (5.8 inches). So, despite the fact that lots of 'little' cars have actually upsized their dimensions enormously over the years, the STi Impreza is still thankfully much smaller on the road than the old Holden.
Smaller, but it weighs about the same.
And what about little cars way back when? The AlfaSud Ti from the early 1980s weighed 895kg; the equivalent - say, the Alfa 147 of today - weighs 1270kg. That's 42 per cent more!
Going up a size, the Datsun 200B from '78? A Jenny Craig success story at 1090kg, or the Celica from the same year? - a very similar 1055kg. The current Celica is one of the few cars not to have put on a disproportionate amount of weight - it's about 1150kg. (More on the lightweight Toyotas in a minute.)
Even the biggest, heaviest, V8-engined luxury cars of 25 years ago didn't actually weigh all that much - the Mercedes Benz 450SEL tipped the scales at 1765kg. These days you'll find a Mercedes S430 weighing about 100kg more - but to the company's credit, that's not the enormous percentage increase that's seen in other classes of cars. But the stretch limo BMW L7 is probably actually closer to the concept of the old 450SEL - and the BMW weighs 2.2 tonnes.
So what about coming a bit closer to the present time? When it was introduced, the VN Commodore had a specified kerb mass of around 1350kg - very light considering the smaller VL (depending on the trim level) weighed only about 50kg less. These days, a similar base Commodore is about 1580kg - but it's a bigger car, too. Still, that's nearly a quarter of a tonne heavier...
Back in 1988 the stumpy-tailed Honda CRX scaled just 960kg; these days the lightest Civic is 1155kg. The very special Insight, though, is just 827kg.
It also makes pretty interesting reading going back to look at the kerb weights of cars that in the past were dismissed as porkers. The 7M-GTE-powered Toyota Supra Turbo was always castigated for its weight... which was 1590kg. That's within 20kg of a current BMW M3... and how many people have been coming out of the woodwork to say how overweight the Bee Em is?
The Mitsubishi 3000GT? No lightweight at 1720kg, but remember that includes four-wheel drive - and is only 20kg heavier than a current Holden Maloo R8 Ute.
In fact, talking about utes - well, we all know that they're a helluva lighter than the sedan equivalents, don't we? Well, according to Holden, the current exec auto 3.8-litre sedan weighs 1526kg. And the equivalent ute (the 3.8, rather than the SS shown here)? Just seven kilograms lighter!
Why Do They Weigh More?
So what is it that's caused such a dramatic increase in weight over the years - especially of the smaller cars? There are two main reasons - safety, and equipment levels.
A new car these days typically is fitted with power steering, air-conditioning, at least one airbag, and ABS. Twentyfive years ago, there were few cars in the world that came with all that equipment! And, to an extent, these items will all have a similar mass, irrespective of the size of the car to which they are being fitted - one reason that smaller cars have got heavier quicker.
Another reason is that smaller cars are intrinsically more dangerous in a crash - there's less room for the panels to crush (absorbing impact energy) before the cabin starts to get squashed. So the strengthening required in smaller cars to give greater safety again has given them a disproportionate increase in mass.
And when you turn to typical family luxury cars, you can really see where that weight has grown. Two, three, four - or even more - airbags (complete with their associated wiring loom, trigger control units and sensors), electric windows and mirrors, navigation screens, sound systems with six or seven speakers and an electric aerial, climate control systems complete with internal flap motors, cruise control systems - it goes on and on. Try to pick up the complete wiring loom of a late model car and you'll be literally staggering - 30 or 40kg isn't unusual.
Another eye-opener is to lift a recent car's electric seat - when there are separate electric motors from tilt, lumbar, front and rear height, and fore/aft adjustment it's not unusual to find that it's difficult for one person to lift the thing. The DaimlerChrysler seat pictured here even has ventilation fans incorporated into it...
Four-wheel drive cars - like the aforementioned Impreza STi - add an extra differential, driveshafts and a tailshaft, often in addition to a more complex gearbox. Talking about gearboxes, every ratio that's added to a manual or auto box will increase the mass of the system. Over the last 35 years we've gone from four speed manual boxes to five and six speeds, while auto transmissions have risen from three to four to five speeds.
Another major factor in the increase in vehicle mass has been the vast improvement in NVH levels - that's noise, vibration, harshness. From the simplest, old-but-effective techniques of simply adding sound-proofing, right through to tricky bits and pieces like hydraulic engine mounts, they all add weight. The current AUIII Falcon, for example, has a sandwich construction firewall - two layers of steel with a sound-deadening agent between. Effective - but heavy. Even when using sophisticated noise mapping techniques like those shown in this diagram, it's almost impossible to have a lightweight car that is also quiet and has low NVH - perhaps in the future, active sound cancellation may provide that answer.
Getting it Off
Manufacturers are very much aware that every extra kg they add means that on-road performance will suffer. They are especially concerned with the negative affect on fuel consumption, and spend enormous amounts of money getting the mass down as low as they can. But the money inflow is vital - it's no surprise that when in a moment we look at some of the real lightweights of today, the companies that have built them are either very engineer driven - or cashed up.
A number of techniques are being used to decrease mass. Steel - previously almost universally used to form monocoque bodies - is being replaced in small mounts with aluminium, magnesium and plastics. There is already about 3.6kg of magnesium used in a typical current car. The steel producers are also fighting a rearguard action - quite successfully, too. The use of tailored blanks (where sheets are made from different thickness steels - the meat going where the strength is needed) and of high tensile steels has reduced the weight of the bare body quite substantially - but self-evidently, only in cases where these techniques are being used. The laser welding of these special steels also has mass benefits.
The hydroforming of frames (where water pressure is used to balloon out metal into shapes otherwise difficult to get without increasing mass) is also becoming widely adopted.
But again, each of these techniques costs money.
The Lightweights
But not all cars these days are disproportionately heavy for their size. Given their equipment and safety levels, there are some real lightweights out there.
Some of the real cheapies are pretty lightweight... but that's because - like those cars of the '70s - you wouldn't want to have a crash in them. And air con and all the rest are either optional or not there at all.
The Peugeot 206Gti at 1050kg is one of the lightest current cars on the road, pretty well lineball with the Renault Clio Sport at 1055kg. Even better than that is the Toyota MR2 Spyder - exceptionally light at 975kg. Of course, if you want to go minimalistic, the Lotii are super lightweight (Elise - 710kg and Exige - 724kg). Also worthy of highlighting - especially considering their exemplary safety - are the A-Class Mercedes. The larger engined A190 weighs 1155kg.
The Lancer Evo 6 at 1280kg is no less than 190kg lighter than the new Subaru STi (but then the Lancer panels flex awfully easily, too), while the 1085kg Mazda MX5/Miata is commendably light, considering its relative soft-top stiffness. The Porsche 911 Carrera 4, especially taking into account its body rigidity and four-wheel drive, is surprisingly light at 1375kg.
For its size and carrying capacity, the Toyota Tarago is a lightweight at 1614kg (consider the Chrysler Voyager's beefy 1848kg), with many Toyota and Lexus models being relatively light. At the opposite extremes, the Echo is only 865kg and the LS430 1830 kay-gees. OK, so 1.8 tonnes ain't light, but remember that the big Lexus
is big and carries every safety and convenience option you can poke a stick at...
And if you want to go to the other extreme, look not towards cars but at trucks masquerading as carriers of people. The heaviest luxo Pajero is just over two tonnes, while - making a liar of us - the Lexus LX470 4x4 squashes the scales to the tune of 2.5 tonnes!
For more information on lightweight technologies:
Laser Welding
Hydroforming - Part 1
Hydroforming - Part 2
Magnesium - Coming Soon to a Car Near You
Footnote: The vehicle masses quoted in this story have been assembled from a variety of sources - manufacturer's data, magazine figures, new car buyers' websites. It's not hard to find three or four slightly different figures for any one car, so all of these figures should be taken as approximate only. We're happy to correct any figures that are wrong if the correction is derived from a weighbridge measurement of a dead-standard car.
