A fastback vehicle is defined as a vehicle that has a long curving downward slope extending from the highest point of the roof to the edge of the trunk, and the fastback is the part of the vehicle from those points on the roof and trunk. This design first originated in the 1930s with aerodynamics in mind. Their popularity has vacillated over the years, but fastbacks are currently in style.

The roof sloping down on the back uses a bit more material, but it can be better for both aesthetic and aerodynamic purposes, and these are some of the most solid cases for why a fastback on a Mazda Miata would be a welcome addition.

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More Aerodynamic

Silver Mazda MX-5 Miata RF
via Car And Driver

Adding a fastback to the Miata actually has a practical use; fastbacks are more aerodynamic, increasing speed and decreasing the drag coefficient. A practical advantage of a fastback design is that those cars are more aerodynamic. The drag coefficient will be lower, despite lacking a wind tunnel.

This design first arrived following World War II, and this design deliberately kept aerodynamics as a factor. The notchback, the design counterpart to the fastback, has 20% more drag than a fastback does.

When fastbacks are being designed, the manufacturers have to take several things into consideration to keep the vehicle aerodynamic: the amount of glass on the windows, the rear spoiler (if there is one), the length of the nose, and the front end as a whole. Force is increased when less glass is used on the side windows.

There's also a semi-fastback design available that compromises between fastback and notchback; this design results in no change in the side forces, only 40 pounds change in lift, and a significant axial force reduction of 8%.

Adding a fastback to the Miata would therefore result in a lower drag coefficient and a more aerodynamic design, making it a highly-sought after modification.

They're Retractable

Red Mazda Miata Fastback in front of bare trees, side view
via Chicago Tribune

One nice feature of the fastback is the retractability with certain models. In the case of Mazda vehicles, such as the Miata, they retract, making an instant convertible. Thanks to the popularity of the PRHT model on the outgoing NC-generation Miata, Mazda decided to incorporate this retractable fastback on the MX-5 Miata RF, with RF even standing for “Retractable Fastback.”

The fastback goes all the way from the roofline to the trunk. The lid raises to allow the roof to fold away, looking similar to a Ferrari 488 Spider or McLaren 650S when the fastback is retracted. The retractable fastback can be raised or lowered at six MPH, and its addition does not detract from the trunk space, so it will have the same amount of trunk space as the standard Miata MX-5 without the retractable fastback.

However, the added weight and possible additional cost have yet to be revealed. In an interview with automobilemag.com, Mazda North America president and CEO Masahiro Moro went on to praise the car's retractable fastback, saying, "From a hundred yards away, this distinctive fastback silhouette ignites the heart of the pure driving enthusiast. We've made MX-5 Miata better in each generation, but we've never lost sight of what matters.”

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Public Was Saturated With Them

Blue Mazda Miata Fastback in front of snow mound
via New Atlas

When hatchbacks first caught on, the public loved them. Then they got sick of fastbacks. Now fastbacks are coming back into style.  One scenario was with the Hornet. Even though that car was doing well on the NASCAR circuit, the design was looking dated, and the fastback did not help its case, even with the addition of several trim changes, minor cosmetic facelifts, and other semi-significant redesigns.

Because nothing was really done to promote or improve fastbacks at the time, the public began to grow exhausted from having the design incorporated into a lot of vehicles at the time. Buyers were expecting fastbacks to be a trend that faded in and out with the semi-frequent round of design updates done to vehicles between lineups every two to three years. GM even decided to discontinue fastbacks for its vehicles by 1952.

Also, an issue at the time was the shortage of car manufacturing materials, making the removal of fastbacks a practical issue at the time, as the notchback design used slightly less material during manufacturing. Wartime restrictions were tough, even immediately following the war's end.

However, fastbacks have back into style by the 2010s, as material supply is no longer an issue and the fastback has been reincorporated into modern design styles. Adding it to the Mazda Miata would give it a more trendy, modern, and updated look, and it would also distinguish the Miata from prior generations, especially the first generation. There tend to be significant differences between Mazda generations as is, so the public would be more accustomed to having the fastback slip in as a design change between models.

It Can Be A DIY Project

White Miata getting added-on fastback in garage
via Occam's Racer

One man even decided to create his own fastback for his own Mazda, and the end result was actually functional. He took a Miata and installed wood between the wing uprights and modified the angle until it didn't look like an add-on and didn't interfere with rear window visibility.

Aluminum was also added at the base for stability and flexibility, forming the basic shape. All seams were glassed and held together. Adding a fastback is a possible self-installed modification that would improve the Miata if so desired.

Sources: merriam-webster.com, ateupwithmotor.com, aerowarriors.com, quora.com, automobilemag.com, occamsracers.com,

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