Shield the tires - will it help?

[Deezler]

I'm not sure. Sorry for the cell phone pics, but you get the idea.





Whats the goal here? Does an open wheel well into a rounded tire edge (as from the factory) have a lower drag, or does this idea, with the sharp edges and somewhat blunt angle? I'm thinking the reasoning is that the spinning tire creates quite a bit of turbulence, and keeping air out of the wheel wells is just generally a good idea. But I have no intuitive feel for whether the blunt angle of the front piece would just wash even more wake out to the sides of the car.

Would be made of abs plastic and bolted to the bumper. I can't imagine any benefit or loss will be especially noticeable in mpg testing.

So what do you guys think? Either give me the motivation to knock em out, or save me hours of wasted time, haha.

[morkys]

I'd be curious. I upsized my tires/rims from 175/65R 14's to 195/60R 14's and upped the rims from 14 x 5.5" wide to 14" x 6" wide. My rims are lighter than the stock steel wheels though.

I for one would love to find out what fairings would do for tires/wheels.

[Deezler]

I just realized that this design is kind of like a "canard", often used in racing.

From: Automotive Aerodynamics - Sport Compact Car Magazine
"canards generate strong vortices that travel down the sides of the car and act as a barrier. If the canards are positioned correctly, these strong vortices act to keep high-pressure air around the car from entering the low-pressure underbody region, thus maintaining more downforce. If air was allowed to enter the underside, the pressure would inevitably rise, reducing downforce. Therefore, these strong vortices act like a virtual curtain or dam, restricting higher-pressure air around the car's sides from entering the underbody region. As a result, the low pressure under the car is maintained and downforce is maximized. Unfortunately, canards are not very efficient, since the strong vortices create a significant amount of drag. They are more useful for fine-tuning aerodynamic balance."

This is kind of ridiculous though:
Splitters-Canards-Winglets - CB7Tuner Forums

[Otto]

It will help, most if you properly fair the device gently so the outer edge of the tire is protected from wind blast. Also, air turbulence behind the tire should be faired, and that's the other half of the battle.

[Bicycle Bob]

Aye. The angle of the front fairing may be fairly steep if the wheelwell happens to be a cooling air exit. You could tape on a few streamers to check how the air flows now. Behind the wheel, you want the usual 15 deg or so recovery, or a continuous shape to the rear wheel, and you want a rounded front edge as well. This stuff pays well for detailing as well as basic shapes.

[robertwb70]

This (small) picture might be of some use

[jime57]

Can't read anything on the picture. Can you resize it. Where did you extract it?

[robertwb70]

I'm on a public computer right now so not much I can do right now but the image is just a link from here

http://image.circletrack.com/f/techa...4_aero_5_z.jpg

The basic idea is that the air coming off the front of the car (to the sides) has some lateral momentum and may, in some designs, largely skip over the wheel well openings. This came up in discussion about the diverters I put on my car a while back (you can see pics in my album).

I seem to remember MetroMPG testing front wheel skirts for his metro and not seeing any improvement IIRC.

[morkys]

My personal concern is that my wheels are open spokes. I was worried air flow was going into the wheel and the open spokes are causing drag. That is why the wheel fairings / skirts interest me. I guess I'll have to research the differences of wheel surfaces.

[robertwb70]

Found the bigger version

And the text that goes with it-
"As the car travels through the air, some of the airflow is directed around the nose and to the sides of the front fenders and wheelwells. If the sides of the nose are angled from a top view, the air will flow out away from the wheelwells and create a very low-pressure area just outside the wheels. The air under the hood is mostly stationary, and some of that air rushes to the wheelwells to fill the void created by this suction. This creates a low-pressure area under the hood, and the pressure differential between the top and bottom creates the downforce needed to provide more grip in the front of the car."
From- Aerodynamics - Tech & Definitions - Circle Track Magazine

Probably not 100% true for many FWD cars (like mine) since the wheel well is separated from the engine compartment, but the idea for the outside flow is relevant.