In a typical Transportation Design class you may hear that everything about a car is designed for a reason. That is to say, Functional, Intentional. Style comes in to make that striking. Beautiful. So while Style may be subjective, Design isn’t. No, not especially with the elements that make it, such as in this particular case, a spoiler. For purposes of clarification we refer to the “front” spoiler, not as such, but as air dam since it mainly prevents the flow of fast-moving air from going under the car that may otherwise cause aerodynamic lift.
Design must answer at least one question. That said, what does a spoiler do for the Lexus RX? 300, 330, 350, or 400h? Really, it’s not just the Lexus RX but a trait of a number of SUVs on the market today. Look at the Toyota Highlander, BMW X5, JLR Range Rover Sport, Infiniti FX, Hyundai IX, Nissan Murano, Honda CR-V, etc. Take note here first that aerodynamic performance is a premium. Then follow with the rest of the consideration.
If you asked manufacturers doing them they could ask you back to look up “spoiler” and what it does for a car. Which is why we should look up spoiler on Your Right of Way! today and see what (if anything) it does for a car and if the SUVs need it or not and really what the truth about this “trendy” feature is. Really, as far as a car’s exterior Design is concerned it should leave the car with a superbly smooth airflow about it when it’s in motion. So, why “spoil” this air?
A spoiler is as the name suggests a construction on a car whose function is to “spoil” unfavorable air about the rear of a car when it is in high-speed motion, redirecting the fast flow up to prevent drag or turbulence. Picture a car’s nose making the first impact with surrounding air, which it begins to oppose as it moves, cutting through it as it moves faster, exponentially increasing the speed of the air, as the latter gushes backward over the entire surface of the car. I’m actually saying car now, not SUV yet. So, picture a car shape.
As the air hits the front bumper and splits, some flowing underneath the car, an area of high pressure is created at that point as well as at the windshield wiper area where the car takes a second hit (or restriction) of air. As the air flows unrestricted all the way to the car’s rear, it apparently tumbles down, therefore the pressure at the rear is obviously lower. Note that, as the very opposite of an airplane, the car’s reverse airfoil shape, and by virtue of the fact that it sits low to the ground, already means that underneath there’s low pressure and above high pressure so that it is pinned to the ground with generally sufficient downforce. But, this difference in air pressure front and rear, as we just referenced, can create drag at the rear, that pulls the car backward and requires more engine power to keep the car in uniform, straight-line motion, meaning more fuel to burn and more emissions. Bad, right? Horrible! This is the justification for a rear spoiler. But, since we’re talking about Purposeful Design here does such a case really require a spoiler?
The plain answer is no. In fact, as far as passenger cars are concerned, a rear spoiler is a wasteful Design, except if it helps with Aesthetics. But what if it helps with Aesthetics and hurts Aerodynamics? And what if it doesn’t help with Aesthetics either? Automakers like to trick our eyes to accept their whimsical styles as the norm! The need for anything to support laminal airflow at the rear of a car doesn’t come until the car is traveling at speeds in excess of 100 kph (62 mph) and may be entering corners without necessarily braking, in which case, a wing, not a spoiler, is the big deal to maintain stability and high-speed maneuverability. Ordinarily, and according to local legislation we hardly travel at such speeds. As to this, for race cars or for demonstration purposes, the wing or reverse airfoil, redirects the air while letting some flow through as its very Design separates the air flow, thus preventing lift, increasing downforce, without creating any turbulence or drag, so providing greater lateral stability to the super-speeding car. In such a situation, a spoiler would only block the air flow and create an area of high pressure at the rear, turbulence, therefore drag. Making worse of an already bad deal. So, it is even bad in such a scenario! And a car is better and can do without one.
So really street cars need no wing. It’s fitting then that higher-end sportscars and supercars are now designed with active wings that rise from their cradle at the speed at which they are required as pre-programmed. For example, the McLaren P1’s rear wing can extend from the bodywork of the car by 5-inches on the road when speed is in excess of the legislated normal of 100 kph (or 62 mph) and grows to about 140 kph. The same wing can extend up to 12 inches high when top speed is in excess of 200 kph (of course, nobody will try that here!). The Porsche 911 Turbo is designed to do a similar thing, and so with a couple of them. This is what we may comfortably refer to as Purposeful Design – it rises to work when it is absolutely needed and sleeps way in when it is not. In fact, the wing is hidden within when on the street!
It doesn’t seem honest to mount a rear spoiler on an SUV! The SUV body type is the result of emphasizing Practicality over Performance, and that is both Reasonable and Purposeful. By virtue of its very own shape, an SUV’s center of gravity is already so raised that hardly anything would prevent risk of rollover at high speeds. Perhaps, a large wing could but how’d that look on an already blunt and oblong surface? And again to be more Capable and Versatile SUV suspension cannot support the kind of speed that needs a wing, even if its engine has twice the power that that may require. Therefore, it is clear that some manufacturers do this just for show and others merely follow the trend but it’s a purposeless piece of metal, carbon, or plastic attached to the vehicle. Look at that RX again and see how the spoiler blends with the horns, or roof rails. Both purposeless, when you know, this kind of car, a CUV – a city SUV – carries nothing on the roof, and both hurt aerodynamics! The Lexus RX would be a finer, more pleasant car to look at if it lost these excesses and you should picture that. You notice this same RX has a small short “wing,” or airfoil, right at the middle point of the C-pillar on the roof? Look at that, and ask again, what purpose does that serve? How would the car behave without that? And what’s that do for the car? Really, the Lexus RX is, and has always been, a car.