| This post is borderline inappropriate, and if it doesn’t get me cancelled, should probably classify me as a boomer. Enh. |
The three-box sedans of my youth had well defined shapes, with a long hood, flat roofs, angled rear window, and flat trunk. These days cars have elongated shapes that blend together front to back.
If you compare a sedan from 20 years ago with a modern one, one design element most new cars share is a big butt. What I mean by that is, the trunks are much higher and wider. This shape brings the deck lid closer in height to the roofline, and when you blend those together, it’s creates a very efficient fastback shape.
Everyone is doing it, and you can’t tell where the roof ends and the trunk begins. The line between hatchback and sedan has blurred to insignificance. I can no longer tell a Honda Civic from a Chevy Malibu from a whatever.
This isn’t surprising, because when performance is the driving factor, designs often gravitate towards function. I saw the same thing in skateboarding over the years. Shapes changed from skinny banana boards, then to pigs, then to fish, and now everything is a popsicle.
To get back to the shape of cars, if you look at them from the side, most are shaped like airplane wings, meaning they have a cambered profile. As air moves over the top of the car, it creates lift. The more exaggerated the curve, the longer air stays attached, and more lift the car generates. As such, a low trunk lid keeps air attached longer, meaning less drag, but more lift.
On the other hand, a taller trunk (bigger butt) means a more gradual backlight angle, which reduces drag. In addition, air breaks away earlier on a taller trunk. Both of these factors improve performance.
Big butt genetics
Cars with big butts have evolved because they have advantages.
- Less drag
- Less lift
- More trunk space
- Fucking hot
Like many performance related genes, big butts have their roots in racing. Read any car magazine and you’ll eventually run into these cliches: “Win on Sunday, sell on Monday,” and “Racing improves the breed.”
Historically, NASCAR had great success partially because people could recognize the cars underneath. The bodywork followed the lines of factory cars (more so on the previous generations), and you could buy a semblance of one on Monday. There were of course many changes under the skin, but one of the key external differences NASCAR allowed was that you could raise the height of the trunk.
Similarly, BMW built the E30 M3 to go production racing, and one of the important elements in the design was to reduce rear-end lift. BMW accomplished this in a similar fashion by making the E30 M3 trunk 1.6″ higher than a E30 trunk.
Big butts improved the racing breed, and that gene is now dominant in production cars as well. As this relates to the only car that matters, each generation of Miata has had a trunk that’s higher than the previous.
The first generation Miata had a flat ass, but she was just a kid back then, and it was normal for that age.
The NB grew up a little, and got a lady lump in the middle of the trunk.
The NC was like a Miata who went to college and put on the freshman 15: bigger everywhere.
Now in her dirty-30s, the ND is slimmed down, with a butt that is higher, boat-tailed, and pert.
Get sprung
The first rule of a production car is that it needs to sell, and that’s based more on appearance than function. But the public has embraced that form follows function, and now big butts are the norm.
Here’s some pics from PornHub.
Occam's Racer 