Body Structure Aluminum Content

Aluminum content of a car is probably the most important characteristic that determines the class of a vehicle. As we go from entry level cars like Corolla to high-end cars like Corvette we go from cars that have very little aluminum in them to cars that are almost entirely made of aluminum.

You probably think that is just because Corvette is a sports car and Corolla is not … but you would be wrong.

Because Range Rover is clearly not a sports car and yet is also made entirely of aluminum. Why ? Because it’s an ULTRA PREMIUM vehicle.

so whether it’s Chevy Corvette, Audi A8 or Range Rover they are clearly very different cars but what they have in common is their six figure price and their aluminum construction.

Aluminum itself is not expensive - plenty of cheap aluminum patio furniture - the reason it is not widely used in cars is because it is harder to work with than steel. It is not easily stamped or welded and so making a car out of aluminum ultimately costs more.

However aluminum has much higher strength to weight ratio than steel and is also much more corrosion resistant which basically means that aluminum content of a car ( versus steel ) is a pretty clear indication of overall car quality.

Cheap cars are steel. Ultra-premium cars are aluminum. Mid-range cars are mostly steel with aluminum used where practical.

What is great about this metric is that it is often possible to find this information about a car using a google image search. For example here is my Volvo S60:

i searched for " Volvo S60 Body Structure Chassis Aluminum Content " - when you know what you’re looking for you will instantly recognize the relevant graphic in image search results.

as you can see in the image there is very little Aluminum in the Volvo S60. just the crash structure, strut brace and of course the cast aluminum strut towers which are made that way in basically all modern cars.

to quote from the article from which i took the image above:

The 2019 Volvo S60 body structure uses Boron steel which accounts for 33 percent of the car’s body weight. Previous models used this Boron steel in up to 10 percent of the construction of its cars.

so the quality of steels used went up from previous generation but aluminum use is basically nonexistent.

this low level of aluminum use is indicative of Volvo S60 being an affordable vehicle. the car does have aluminum engine and probably some other parts like the hood not shown here may be aluminum as well, but again, these are fairly standard uses of aluminum and do NOT indicate a high level vehicle.

now let’s look at Porsche Panamera

the use of aluminum here is clearly much greater. to quote from the article from which i sourced the image:

The hood, front fenders, body side panels, and roof are all aluminum. The basic structure comprises a mix of aluminum and high-strength steels.

and that’s of course because the starting price of Panamera is MORE THAN DOUBLE the starting price of Volvo S60. furthermore Panamera platform was designed to underpin Bentleys down the road ( which it now does ) so it is a much higher level platform than the one on which Volvo S60 is built obviously.

without looking at this type of information it would be very hard to understand why the Panamera costs so much more than Volvo considering the top-end Volvo powertrain is 455 hp for $60,000 while the entry level Panamera powertrain is 348 hp for $100,000 …

what most people don’t understand is that the chassis is the most expensive part of the car, not the drivetrain, not the suspension and not even the interior

automakers have the option of simply buying a good engine like Range Rover buys the V8 from BMW for example … most other parts of the car like transmission, seats, brakes, airbags etc. are all also purchased from suppliers. on the other hand the chassis requires building an entire assembly line if not an entire factory for.

the chassis is essentially, above all else, what makes the car what it is.

the good news as i said is you can usually find this information if you know to look for it. at the very least the cars that are built on GOOD platforms will probably have that information available, even if only as a figure like “60% aluminum content” though an actual image would be better.

by the way here is 1st generation Panamera

the important thing to note here is the green in the rear is the cheap basic-bitch steel. in the first generation they use it there because it is cheap and heavy to balance out the weight of the V8 engine in the front.

by the end of 1st generation run they have started implementing plug in hybrids with battery in the trunk so for 2nd generation they replaced the cheap steel in the rear with aluminum because they now have the weight of the battery in the back.

so in effect the hybrid battery doesn’t really add that much weight to the car, because the weight was already there - but it used to be dead weight of cheap steel.

2nd gen Panamera uses cheap steel in the middle part of the car while the nose and tail are aluminum. this is to reduce polar moment of inertia. of course having engine in front and battery in back doesn’t help with polar moment of inertia sadly, but they at least try to counterbalance it with material use.

so in 1st gen they use steel to balance weight distribution but in 2nd gen they use aluminum to reduce polar moment of inertia.

polar moment of inertia basically means how much energy the car carries when spinning out - thus how hard it is to stop that spin. it is better to have the weight of the car all in the center like in an EV than to have half of the weight in a the front and half in the rear like in Panamera Hybrid. of course EVs aren’t fully mature tech yet.

anyway in both generations hot formed boron steel is used for side impact protection in roughly the same places. boron steel is used because it is strong. my gym padlocks use boron steel shackle because they are harder to cut for example.