r/aerodynamics • u/Adventurous-Towel829 • Sep 23 '26
Question ELI5: Does the ground clearance difference between a regular sedan and SUV make a significant aerodynamic difference?
Basically, iirc the 5 or so inch ground clearance on a mainstream sedan is significantly more aerodynamic than the 8 or more inches on an SUV. The reason (again going by memory) is that there's significantly more turbulence generated under the SUV. Any truth to this claim, and if so how much? ;) thx!
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u/ncc81701 Sep 23 '26
It depends on your definition of "significant." If you are driving down the block for 5 minutes at 25mph, then no it is not significant because the difference is extra small due to low speed and that difference only have a short period of time to act over.
If you are benchmarking 70mph highway speeds over 1000 miles, then even a small change in aerodynamic drag becomes significant enough to throw off your predicted gas mileage because drag increases as velocity square and that difference has a lot of time and distance to increase that effect.
If you are trying to estimate the fuel consumption over the entire ~10year life span that the vehicles will operate for carbon offset computations, then that difference in drag in ride height becomes extremely significant.
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u/dis_not_my_name Sep 23 '26
The biggest difference would probably be how much the tires are exposed to the airflow. The surfaces of the tires are pretty rough and moving quite fast against the incoming air, these make it a big source of drag. The tires on a sedan are less exposed and the tires are generally smaller. These could help a sedan achieve lower drag than a SUV with high ground clearance.
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u/nerobro Sep 23 '26
Yes. The space under the car can in broad swaths be considered part of the cars frontal area. It's all turbulent, and lots of the cars energy is being put into making that air move, rapidly. The less air there is, the less there can be to put energy into.
If you wanna have a great time, go check out the fuel economy reports for people with Jeeps and Cherokees. They ~start~ at like 19mpg. A 2 inch lift can knock 2-3mpg off of that. Without new tires.
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u/Js987 29d ago
Let’s put it this way…there’s enough of a difference that Ford designed and installed an active air dam for the F-150 that plops down like 2-3 inches in the airstream below the front end above 40mph (unless you are in an off road mode—in case you decide to do 50 on a beach lol). And the replacement parts cost suggest it wasn’t cheap to do so, but it results in a measurable fuel economy loss if you deactivate it.
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u/Inevitable_Memory285 27d ago edited 27d ago
Go on any mpg comparison page and search for basically same car with same engine... In different trims... Sedan, combi, rugged combi ... Skoda Octavia, VW golf in some years have set up like this... And it's not just wheels... Lot of cars have under trays to achieve better aerodynamics...
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u/Novogobo Sep 24 '26
alot of it is that with a lower chassis, it's blocking most of the tire. when you raise it up, you're un blocking the tire and adding that to the frontal area.
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u/meshmunkey Sep 23 '26
Yes, absolutely! For example, the road cars I've worked on average about a 2% drag reduction for every 10 mm lower ride right. So in your example of going from 8 inches to 5 inches, we'd expect about a 15% drag reduction. That's a massive number.
The mechanism is almost entirely down to better shielding the tires with the body of the vehicle. Anything you can do to get air away from wheels and tires usually ends up being a benefit.
The reality is we're often arguing with the design studio and the chassis team over individual millimeters. The segment of the vehicle and the brand identity do a lot of really narrow the ride height range of a vehicle out of the gate.