Silverado Aerodynamics

[Taylor95]

Some of you may have noticed that there are some differences between the regular Silverados and the SS versions. Assuming the two pictured below have the same aerodynamics underneath the vehicle and the same tires and wheels, which do you think have better aerodynamics? Why?

[Hersbird]

If all other things were the same, wheels, tires, ride height, fender flairs, bed covers, mirrors, etc. And the only difference was that bumper cover I would say there would be no difference. Although the SS cover looks lower, the regular setup has a rubber deflector tucked back that sits just as low and would accomplish the same thing.
But the SS does have no fender flairs and a lower ride height. Problem is, a thirsty 6.0 motor and a heavier duty automatic that has more parasitic losses.

[kach22i]

Does the SS have an extra set of do-nothing air inlets in it's chin apron?

That is NOT good, they should be blocked off.

They are there for looks and do not duct to the brakes like on a race car.

We need much better detailed photos FYI.

The devil is in the details if the ride height and under-trays are similar.

Hard to tell from these photos if the SS uses colored wheel flares or none at all - wheel flares in any case typically cause more drag.

The SS has low profile tires, why are we to ignore this?

[Taylor95]

I am more interested in the aerodynamics of the body than the tires. But it doesn't really matter. I was also wondering what those holes in the front of the SS were for. Does anyone else think that the more squarish shape of the SS has a detrimental effect on aerodynamics? I would think that the more rounded shape of the other versions of the Silverado would aid FE better.

[Hersbird]

Originally Posted by Taylor95

I am more interested in the aerodynamics of the body than the tires. But it doesn't really matter. I was also wondering what those holes in the front of the SS were for. Does anyone else think that the more squarish shape of the SS has a detrimental effect on aerodynamics? I would think that the more rounded shape of the other versions of the Silverado would aid FE better.

I think the roundness of the front is an illusion from the angle the picture is taken. The SS has the same front end only the bumper cover is different. I have actually thought about using that cover on my Yukon XL. Technically a factory cover would require some modification but there are under $200 aftermarket ones in that style. I don't think it would help aero but it's pretty IMO

[Vman455]

It's impossible to say with any degree of certainty. You can't measure the drag coefficient of an object by looking at it. Try it; what are the drag coefficients of these trucks?



...versus this:



...versus this:



...without seeing Chrysler's own numbers. Go ahead, take a guess.

***

The answers are (select to show text or click link for source): #1) Cd .42; 2) Cd .399; 3) Cd .36.

Chevrolet has never published drag numbers for the Silverado, so the only way you're going to answer your question is to track down an engineer who worked there and is willing to divulge that information. Good luck!

[kach22i]

Originally Posted by Vman455

...without seeing Chrysler's own numbers. Go ahead, take a guess.

I took a pessimistic stance and was right in the ballpark.

I was hoping that I was wrong.

I think Ford's numbers are quite a bit better, but still bricks.

EDIT:
Aug 2014
Ram says they improved their Cd
https://www.motortrend.com/news/2015...f-series-ever/

Another Aug 2014
http://www.trucktrend.com/news/1408-...ullsize-truck/

[freebeard]

I don't see the difference. What year Silverado is that? My son bought a 2018, but the big advance is on the 2019 models:


gmauthority.com:2019 Silverado And Its Aero-Enhancing Air Curtains: Feature Spotlight

[Hersbird]

Vman, I would question those numbers thrown around by Ram and the journalists. The guy delivering the truck to a media event or standing by it at the car show probably gets a few things wrong as does the journalists taking notes. There is not that great a difference between the first and last. Also as demonstrated in the 2019 version EPA ratings, the makers get to use their best numbers available in the test even on the worst packages. Case in point the Rebel with higher ride height, big mud tires, and less air dam gets no penality in its EPA rating. Real world it's a good 3 mpg hit.

[Vman455]

Originally Posted by Hersbird

Vman, I would question those numbers thrown around by Ram and the journalists. The guy delivering the truck to a media event or standing by it at the car show probably gets a few things wrong as does the journalists taking notes.

Straight from the horse's mouth:





2009 Quad Cab: "The cooperative application of aerodynamic science and innovative styling led to aerodynamic improvements on the new Ram that resulted in an estimated coefficient of drag (Cd) of .422 for a crew cab 4x4 model – compared with a Cd of .463 for a 2008 Ram Quad Cab® 4x4."



2014 Quad Cab: Chrysler's 2014 Ram press kit--as well as the press kit for every subsequent model year up to 2018--says, "Best-in-class aerodynamics, coefficient of drag (Cd) at 0.360."

I don't buy an argument of communication error with journalists (in this case) when those are the numbers FCA actually published. Yes, the differences are very subtle, but that's kind of the point here. Those subtle differences account for a range of more than 60 counts in the drag coefficient, or more than 100 counts comparing the 2008 to the 2014!

Try another one: 2019 Ram 1500.



Answer: Cd .357

To get back to the original question: it is impossible to say just by looking what the difference in the drag coefficient of two trucks is.