Eccentric Doors – Your Guide to the Difference Between Butterfly and Dihedral

It is generally agreed that there are now seven major door types for cars – ok, six, if you ignore the widespread conventional ones we get on the majority of cars in existence at the moment.

All of these six, the ones we like to call eccentric, open differently than what you might find on the average Joe's car, and they can be included in the following categories: butterfly, suicide, gullwing, scissor, sliding, and swan doors. Evidently, there's no need to discuss the standard design that you find on most cars on the market, because you all know how those work.

In this story, we will be focusing on the types of doors we most commonly get on the most exquisite of cars, the ones that play in the supercar and hypercar segment. Granted, every now and then, a company does come along and brings an unusual design in a mass-production model, but these are exceptions.

So brace yourself to learn a thing or two about dihedral doors, scissor doors, suicide doors, butterfly doors, and gullwing (aka falcon) doors. As said, we left out conventional doors, but also sliding doors, firstly because there are so few of them around these days on passenger cars, and secondly because they never proved themselves worthy of volume production.

Dihedral doors

A dihedral door may not sound that familiar, and that's because it is one of the most recent kind. Its name draws from the world of geometry, where it represents something that has or is contained by two plane faces. For its use in the automotive industry, the term stands for the actuation system that allows a door to open or close.

The way this mechanism is made allows the doors to rotate 90 degrees by sweeping outwards and upwards right where the hinge is – in this case, that would be right on the A-pillar. In simpler words, the door opens to the side and then it moves up at an angle.

In case you're not entirely a thing on today's cars, take a look at the models a company called Koenigsegg makes. It is the likes of the Jesko or CCX that first used this design, and to some it looks a design as revolutionary today as the one on the Lamborghini Countach looked like back in its day.

There are a number of advantages of having a door open this way, including the vey large aperture created, but also disadvantages. For instance, if you park too close to a high object, the door could suffer some damage when it's opening and closing.

Scissor doors

The style of the "scissor door" was made famous by the Lamborghini Countach back in the 1970s, but the system was actually introduced a little earlier, in 1968, on the Carabo concept made by another Italian carmaker, Alfa Romeo.

Despite being so old, the design is still in use, and because Lamborghini is the one that deploys them the most (but not the only one, as it can be found on the likes of the Spyker C8 or Bugatti EB110 as well), they also became known over the years as Lambo doors.

Naturally, Lamborghini does not use this type of door on all of its models, and on others, such as the Aventador, it uses a variation of the system that takes the doors slightly outward at an angle.

The way this type of door works is pretty simple: there is a hinge installed at the front of the door, but one that instead of rotating outwards as it does in a conventional door, it moves up vertically.

There are several advantages of this approach, the biggest being that when parking in very tight spaces you don't really need extra room. The biggest downside is that there may be issues when parking in places that have rather low ceilings. In that case, you might end up crawling out of the car like Leo DiCaprio in The Wolf of Wall Street.

Scissor doors are also quite popular in the aftermarket world, with plenty of conversion kits available for a wide range of popular cars. But no matter what vehicle you convert this way, it probably won’t feel the same as the original Lambos do.
Suicide doors
Despite its scary name, this type of door design was quite popular a few decades back. It's not exactly clear why the term was chosen, but it probably has to do with the fact that trying to close this type of door while on the move would require a huge and dangerous effort, as the person would have to resist the airflow.

Why is that? The answer is simple, really. In suicide doors-equipped cars, the ones at the front open in the opposite direction to the ones at the rear because of the way the hinges are positioned.

Officially called rear-hinged doors or coach doors, this system used to be all the craze some decades ago, but that is no longer the case. Both makers of volume cars like Mazda, Saturn, and Opel/Vauxhall, but also luxury brands like Rolls-Royce (the Brits still use suicide doors), they all had at some point cars in their portfolio whose doors opened this way.

The main reason behind it is that such an approach improves access to the car, especially to the rear seats, as it really opens up the sides. As for disadvantages, there aren't really that many, and most of the things on such a list have to do with the occupants being careless in operating the doors and potentially damaging the car or hurting themselves or pedestrians.

Butterfly doors

Butterfly doors are perhaps the most spectacular of the entire bunch. They are named so because when opened they kind of look like the wings of a butterfly, and they really add a touch of class to any of the supercars and other exotic car models on which they are usually installed.

Technically speaking butterfly doors are related to the scissors. They work by moving outward and then up, but they also move forward, toward the windshield, and in time that made them more practical and widespread than their cousins.

The main reason for making doors this way was to allow easier access to vehicles that are not famous for their generous roofline. But as with everything in life, there are downsides to using such an approach.

The first is the fact that interior space is affected by the fitting of butterfly doors, and it also can be very hard to properly use them in cramped spaces or garages with low ceilings. The silver lining is that the cars that use this design are not bought for their generous interior space or their ability to park at Costco anyway.

There are a number of cars that use butterfly doors, including some very recent ones. The most notable are the McLaren F1, Ferrari Enzo, Mercedes-Benz SLR McLaren, Ferrari LaFerrari, and BMW i8.
Gullwing (falcon) doors
Gullwing, or falcon doors, are the ones that are hinged to the roof instead of the side. They are perhaps the most famous of unconventional car doors, not in small part thanks to a German carmaker called Mercedes-Benz and a car known as the 300SL.

Inspired by the wings of seagulls (hence the name), these doors came into this world as Mercedes was looking to make the car more aerodynamic. The 300 SL had an aluminum tube space-frame chassis that enveloped the passenger compartment. This led to the introduction of the gullwing doors as a necessity, not a fashion statement.

But that's not the only advantage it brings, the other very important one being the fact that it allows people to get in and out of the car even in crowded places.

In some cases this approach proved a bit tricky in places with low roofs, so a workaround was devised. When applied to more recent vehicles, such as the Tesla Model X, for instance, the falcon doors come with a moving roof panel that helps reduce the amount of space the doors need to move up.

Swan doors

This type of door looks pretty much like a regular one, as it opens to the side, in the conventional fashion. However, they are mostly employed in models with reduced ground clearances because they can help prevent unwanted incidents. Aston Martin is a big fan of this system, and it used it used on anything from the DB9 to the One-77.

Other automakers have used them for the same reasons, including Pagani on the Huayra, Chevrolet on the Corvette Stingray, and Hennessey on the Venom GT.

The swan doors are an excellent illustration of practicality from supercar makers, as they have imagined the fact that people will drive their creations on public roads. Even the wealthiest of customers do not want to take their cars to the shop to fix door dings, so swan doors were designed to prevent that from happening.

It's safe to say that there are two main differences between these types of eccentric doors. The first is the way they are hinged, and the other, influenced by the position and type of the hinge, the way they open.

Sadly, customers have no choice when it comes to the type of doors the cars they drive have. In a nutshell, if you are a big fan of scissor doors, for instance, the only way to enjoy them is to get yourself a car that has them from the factory. And the same goes for all the others.