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1955 Ford Crown VictoriaUnderstanding Aftermarket Aero Options
Looking into updating the aerodynamics of your car? Here are some of the different aftermarket aero options to look out for!
Improve Car Aerodynamics & Look Cool
Race cars seen in IMSA and F1 feature some pretty incredible aerodynamic additions in comparison to your average car. All these sharp wings and angular body extensions aim to achieve better performance around the track. Racing teams carefully update and tune a car’s aerodynamics to reduce drag, reduce lift, and produce extra downforce on the car.
Reducing drag helps keep the car streamlined, making it easier to cut through the air and reach higher top speeds. Reducing lift helps the car stay planted to the track at those high speeds and can aid in stability and handling. Similarly, increased downforce pushes against the air making the car hug the ground, which aids in tire traction, stability in the straights, and maneuverability through the corners at faster speeds.
If you’re trying to emulate these racing aerodynamics with your Dodge Charger, Mazda RX-7, or Honda Civic – don’t expect to see significant performance around town. Sure, you’ll get the sharp look, but most of the benefits you’d expect from these aftermarket aero options aren’t fully realized until you’re cruising at least at highway speeds. Regardless, if you’re looking to update your car to look like a racer with some extra aerodynamic pieces, we’ve got the list for you. Everything from your most basic aero to some extensive modifications that’ll really transform your ride into an air manipulating beast.
Basic Aftermarket Aero Options
Rear Spoiler
One of the simplest and most effective aftermarket aerodynamic updates you can make is a rear spoiler. These are mounted on the rear decklid or roof of a vehicle to help the air flowing over the body separate from the vehicle more cleanly than without. Before installing a spoiler, air can get caught behind the vehicle as the high-pressure air going over the top is directed directly behind the vehicle creating a swirling vortex generated in association with the low-pressure air flowing from the bottom of the vehicle. This in turn leads to an inefficient pocket of turbulent air behind the vehicle increasing drag. Adding a spoiler helps direct the high-pressure air farther away from the rear bumper helping generate less drag, improving fuel efficiency and even straight-line performance.
Rear Wing
Contrary to popular belief, a rear wing is different from a spoiler. This is typically a raised, and sometimes adjustable, inverse airfoil device that aims at increasing the downforce of a vehicle. This added downforce generated by the wing helps the vehicle gain extra traction, move better through turns faster, and aid in straight line stability. Conversely to a spoiler though, a rear wing will actually increase the drag on a vehicle hurting fuel efficiency and even put additional strain on the engine reducing the top speed. That’s why it’s better for use in racing applications rather than daily driving, but it does look pretty sweet.
Front Splitter
A splitter helps better direct air past the front bumper and aids in additional downforce. On a car without a front splitter, the front bumper is the first point of contact with the air and doesn’t distribute the air efficiently around the vehicle. Adding the splitter puts the point of contact farther away from the front bumper and lower to the ground helping better control the air around the car. This reduces drag while also generating a lower pressure zone below the car producing better downforces over the vehicle at high speeds.
Side Skirts
Side skirts are long additions to the lower sides of the vehicle between the wheel wells. They are installed along the sides of the vehicle in an effort to prevent high-pressure air going over the car from disturbing the low-pressure air below the car. This in turn helps marginally with maintaining downforce. In street application though, it’s just for looks and any changes to your vehicle’s aerodynamic performance will be negligible if anything at all, especially if installed with a stock ride height as they perform better closer to the ground.
Rear Diffuser
A rear diffuser is an undercarriage aero part towards the rear of the car that acts as an expansion chamber as air exits from behind the vehicle. The low-pressure air is redistributed between the sectioned design further lowering the air pressure beneath the vehicle aiding in additional downforces. Similar to a spoiler, a diffuser cleans up the transition from beneath the car to the more turbulent nature of the air behind the car which can help reduce drag further as well.
Canards
These odd little wings that stick out from the front bumper typically are called canards. These aero dynamic dive planes are installed in a multitude of different positions and locations to serve different purposes when it comes to a vehicle’s aerodynamics. Depending on placement, canards can deflect air around the front tires to help reduce drag around the sides, create air vortexes that help seal the bottom of the car aiding in downforce, or work in conjunction with the splitter to dissipate air to the sides of the vehicle reducing drag. However, placement of canards can also disrupt the vehicle’s aerodynamic performance by generating unintended turbulent air in key areas of its design.
Fender Flares
This aftermarket aero part is predominantly if you have wider set wheels that extend past the stock wheel well, but if that’s the case then fender flares can help a little. While technically intended to prevent road debris from being kicked up by the tire tread, fender flares can also help move air past the exposed wheel section reducing drag. Like side skirts, this results in marginal benefits towards actual performance while looking cool.
Extensive Aftermarket Aero Options
Side Mirrors
Now we’re getting into some of the advanced aerodynamic stuff for those that are headed to the track… or just looking to further throw money at their BMW. Side mirrors may not seem like that much of a problem area for aerodynamics, but they do produce a vortex of turbulent air behind them that can throw off aftermarket aero at the rear of the vehicle. To combat this, some will simply remove the mirrors like a NASCAR stock car and leave it at that.
But that’s not an option when considering a car that drives on the street, at least in most states, so an aftermarket option can be the solution. Aftermarket side mirrors produced regarding aerodynamics are typically revised in such a way that they take up less surface area while taking on a more streamlined shape than an OEM example. These side mirrors will also sometimes utilize an integrated miniature diffuser or even their own “spoilers” to help clean up the air going around them.
Flat Underbody Panels
Some of today’s cars already have begun to add underbody paneling in an effort to promote better fuel efficiency, but these don’t cover the recessed sections used for the exhaust system or transmission typically. These open sections beneath the vehicle can lead to unintended drag and generate disturbances in the low-pressure zone beneath the car. By filling those gaps with flat paneling, it creates a more uniform distribution of the air helping the vehicle’s stability and furthers the effectiveness of the low-pressure zone when used in conjunction with a rear diffuser.
Aero Trunk
Installing a rear spoiler is one thing but replacing the trunk with an aftermarket one featuring and integrated spoiler can yield even better results. The small issue with an aftermarket spoiler is that it isn’t a part of the original body work, so there can be some losses in efficiency due to the spoiler being a separately installed unit. Replacing the stock trunk with aero trunk provides the benefits of a rear spoiler while utilizing a seamless design that irons out those marginal losses a standard spoiler may have. It also looks pretty slick.
Hardtop Roof
Some cars, like the MX-5 Miata, were predominantly sold with a soft top roof. Being able to drop the top on a clear sunny day is great, but not necessarily if you’re going around a track. The windshield produces drag already but having no roof leads to even further drag and turbulent air hitting the aftermarket aero at the rear of the vehicle diminishing performance. Even putting the soft top up messes things up as the design isn’t perfectly smooth or rigid and disrupts the high-pressure air over the top of the vehicle.
To fix this on our beloved drop tops, we need a hardtop roof installed. These replace the convertible soft top for a rigid roof form that helps direct air over the vehicle in a more uniform way like your traditional vehicle does.
Body Kits
Aftermarket body kits are predominantly used to show off a unique look on a popular vehicle, but they do provide some aerodynamic benefits. OEM bumpers aren’t perfect when it comes to performance aerodynamics, but aftermarket ones can feature angles that better distribute the air around the vehicle and work in conjunction with the rest of the kit’s body panels to produce an ideal mix of reduced drag and added downforce. These body kits also often integrate items like a front spoiler, rear spoiler, side skirts, canards, and many of the previous aftermarket aero options into their designs.
There are also the wide body kits that not only allow for a wider track with wider wheels but offer aerodynamic advantages too. The extended features distribute air around the sides of the vehicle and wheels better like fender flares do. The wider proportions also help increase the high pressure and lower pressure forces that surround the vehicle, producing more downforce.
What Aftermarket Aero Option Should I Install First?
A rear spoiler is the simplest answer. Out of all of the different aftermarket aero options we laid out here, it’s the easiest to install, the least intrusive design, and provides the most benefit for daily driving. Past that, it’s strictly a design choice unless you are hitting the track. Just keep in mind that sometimes less is more when it comes to messing with a car’s aerodynamics. All these pieces can increase downforce and reduce drag, but extra weight from too many components can bog down a build and hamper those performance gains you were expecting.
