Heresy! Smooth Wheel Covers- Myth Busted!!!

[Tahoe_Hybrid]

Originally Posted by Vman455

Note that the XL1 uses wheels vented at the perimeter as well:

how is that aero when it's sticking out 1/2" or so

[aerohead]

Originally Posted by Tahoe_Hybrid

how is that aero when it's sticking out 1/2" or so

'Sticking out' is an advantage.The convexity of the disc returns a lower drag than a flat disc,even though it aggravates frontal area.The technology dates to the WW-I Curtiss JN-4 'Jenny',of which the wheel covers became the inspiration for the 'MOON' wheel discs.

[ACEL]

Hello All,

A good reading easy to Google and find on the Internet about wheels mentioned by Julian Edgar is from Alexey Vdovin, 2013, Investigation of Aerodynamic Resistance of
Rotating Wheels on Passenger Cars.

The author found out that a wheel with a "thick outer radius cover" was better than the complete cover. Also the Tesla model S aero wheels are of interest. These wheels are almost completely covered but for an open ventilation ring around at the outer wheel diameter.

I intend to test both approaches in the coming weeks and will let you guys know about the results.

[PaulB2]

There seemed to be more variation with changing wind perhaps, than the variation of wheel covers on or off.

Long range shooters prefer to do their stunts at dawn or dusk, when the wind normally dies down. You might keep that in mind. I agree wind has a big effect.

[easythereturbo]

One thing I remember reading long ago is that inset amount of the tire/wheel matters more than anything else. Not that its my opinion but I guess some people think it looks "bad" to have it set way inward in the well. So marketing may keep this from being a viable option on a production vehicle. Makes sense to me that having it set way deep in there away from the air flow across the well would be beneficial. I don't recall where I heard this. I think it may have been a Bonneville speed guy.

[aerohead]

Originally Posted by easythereturbo

One thing I remember reading long ago is that inset amount of the tire/wheel matters more than anything else. Not that its my opinion but I guess some people think it looks "bad" to have it set way inward in the well. So marketing may keep this from being a viable option on a production vehicle. Makes sense to me that having it set way deep in there away from the air flow across the well would be beneficial. I don't recall where I heard this. I think it may have been a Bonneville speed guy.

'Styling' has driven car design since around 1928,when the annual styling change,and design obsolescence became corporate policy at du Pont/General Motors.
CAFE standards have driven carmakers to shave drag wherever they can for mpg compliance.They all know that enclosed wheels offer the lowest drag,but exposed, stupid,custom wheels have become an industry unto them selves.And there's a lot of profit selling stupid wheels to even more stupid consumers.
As long as wheels remain 'exposed',you'll see them as close to the sides of the vehicle body as they can,with the smallest wheelhouse arch gap. When and if aerodynamics ever becomes a priority,you'll see them inset,and covered by skirts,all around.

[freebeard]

Originally Posted by easythereturbo

Not that its my opinion but I guess some people think it looks "bad" to have it set way inward in the well... Makes sense to me that having it set way deep in there away from the air flow across the well would be beneficial. I don't recall where I heard this. I think it may have been a Bonneville speed guy.

An instructive place to observe wheelwell turbulence (on other vehicles) is on the Interstate in a driving rain. Water circulating in the wheelwell is thrown outward much more than the air.

Trucks tend to have deepset fenders and some throw water 2-3ft outward (and onto your windshield).

Arguably, a tire on a rim wider than the contact patch has a better profile that on a rim that is narrower.


https://imgur.com/Cdh4U9B

[easythereturbo]

The "hellaflush" boys seems to have driven marketing to push wheels farther outward. I don't really give a crap one way or the other. Whatever the air prefers is what I prefer. If that means tires sunk way in to the wheel wells I'm ok with that.

[TimRogers]

John Shinella,of Pontiac styling, researched wheel cover drag in the Lockheed Marietta wind tunnel during development of the Trans Am Firebird of 1982.
*The car,@ Cd 0.32,with no covers
*with ventilated flat discs dropped to Cd 0.296
*TAPING over the vents produced Cd 0.290
*Shinella's ventilated convex covers showed Cd 0.287

The only downside of this testing data is that Lockheed Marietta's wind tunnel is not a rolling road type. Without the wheels turning, one of the most important factors of how the turning wheel interacts with the windstream is not represented in the test.

Speaking of windstream, the Windstream wind tunnel in Concord, NC is a modern, full scale rolling road wind tunnel.

[JulianEdgar]

Originally Posted by TimRogers

The only downside of this testing data is that Lockheed Marietta's wind tunnel is not a rolling road type. Without the wheels turning, one of the most important factors of how the turning wheel interacts with the windstream is not represented in the test.

It's actually even worse than that because that car wouldn't have had an underfloor design anything like most of today's cars. (Tesla found the undercar flow influenced the best design of wheel.)