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  • MilesDriven

Heavyweights

Is a future full of heavy cars inevitable

White Porche closeup

It's a problem that any engineer no matter what they are building will face, the more mass something is, the more mass needed to support it. Breakthroughs are celebrated, every time a material comes along and is stronger but also lighter there is an immediate attraction, cost usually becomes the balancing act.

Automotive engineers and even casual enthusiasts will be no stranger to carbon fibre, especially since many supercars now come with an option package just to show off the bare weave of the material. Aluminum is less exotic but has also found its way into headlines in the last decade with commercial vehicles like the Ford F150, and luxury vehicles from Jaguar and Land Rover all using it to trim off some of the bulk their models were gorging their way towards.

Weight is a fairly simple enemy, it doesn't breathe fire or know karate, but it does hinder a car in every single way, whether it's making it slower as moving more mass from a standstill is more energy consuming, or stopping all those kilos. But why does it matter to you, after all, cars have been getting heavier for decades, and yet today they are the most fuel-efficient, safe, and powerful they have ever been.

The problem comes when energy is considered in scarcity, if you having a racing car, being a lightweight has a plethora of obvious advantages, cornering speed and being later on the brakes, not to mention being fast out the corner are all obvious, but many aren't. The lighter something is, the more fuel-efficient it should be, this means beginning the race with less fuel, and so the gain is two-fold, not only is your car lighter than the one next to you, but it is lighter still because it won't need as much energy to complete a race. Then there is the gain from a material standpoint, the lighter the car is, the less strength the structure needs to keep it together. Again a double win, make it lighter, and the components can be even lighter still. Make it heavier and the suspension needs to be beefier, think a Baja rally truck vs a go-kart.


When we talk about cars becoming more efficient we just accept that we are looking for a gradual increase, but what about if a Porsche Taycan weighed 1100kg

Then we come to our problem of today. Name a heavy car, go on blurt it out, it doesn't even have to be a car. Some of you may be saying, 'A tank!', others may say a truck, and then there are the obvious contenders in the passenger car segment, Range Rovers, Rolls Royce, Mercedes S-class, and so on.

The 2021 Range Rover with a 6 cylinder diesel engine weighs 2275kg. Over two metric tonnes, a BMW 3-Series for comparison, 1620kg, this figure will move around by a few kilos for different models, but a roughly 600kg difference. It won't surprise many of you to hear a 3-series is more fuel-efficient, faster in like for like trims and not only stops faster but turns quicker. Now this matters a lot when it comes to driver enjoyment on a twisty section of road, but most people aren't buying these cars for that reason and so won't care, what they will care about is the fact that stopping and turning faster can mean life and death in a crash, especially if a pedestrian is involved. Being agile not only saves fuel, but energy, and since we live in a world where energy is constantly advised to be at a crises point, being light, simple and safer is the obvious preference, right? Well, here's the problem.

The generation of cars being offered to consumers today are getting heavier, a lot heavier, and the problem just metastasises the bigger the vehicle is.

A Porsche Taycan is a slightly larger vehicle than a 3 series, so how much more does it weigh, 100kg? 200kg? no, 700kg, it is, in fact, heavier than the entry-level Range Rover at 2305kg. Quite remarkably the Tesla Model 3 is quoted in at a lower weight than the BMW 3 series on the base model but goes to 1847kg for the dual motor with long-range, the Model X comes in heavier than the Range Rover at 2305kg.

Now that you've got used to the numbers and began to think, well, if they have bigger brakes, and regeneration, then many electrical cars may actually stop better and turning can be achieved through better dampers, and you're right, but the problem of energy remains. A 1996 Honda Civic weight 1026kg, so every time it stopped and started it did so with half the mass, this means materials could be simpler, cheaper, and more fuel-efficient. It also means that if it tragically hit a pedestrian the mass that is moving is half what it would be in many modern cars.

When we talk about cars becoming more efficient we just accept that we are looking for a gradual increase, but what about if a Porsche Taycan weighed 1100kg, it would need a lot less power to be just as fast, and thus fewer batteries, and so consume a lot less energy. This is an answer that is being ignored because technology can't currently answer it, but it will have to be uncovered soon enough and answers given because there is another elephant in the room, cost.

Tires, brakes, suspension, chassis, crash structures, they all must get stronger the heavier you go and that means the more costly, not a problem in the earlier examples of a Baja race truck slapping on heavy-duty shock absorbers, but a massive problem when trying to make a Ford Focus competitively priced. If we let the scales keep going higher, electric cars will remain at their current levels of price, uncompetitive and hugely inflationary compared to their combustion-engined stablemates, not just because rare earth materials are, well, rare, and only get rarer the more you dig out of their resource, but because every component must able to fulfill a heavier demand. The Volkswagen ID3 is roughly 200kg heavier than the VW Golf, add that much weight to Golf and the MPG would slip noticeably, so can we get lighter and cheaper...

Mass, it's the enemy we know, and yet one we are still fighting.

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