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Old 04-24-2008, 03:32 PM   #1 (permalink)
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Question Wheel wells

I drive a truck, and the rear wheel wells are fairly cavernous, check out the garage for vehicle details. I'm sure they serve as some form of drag.

So, short of putting larger rubber to fill the hole or skirts to close off the area completely, can I put a small (3/4" or so, larger or smaller) protruding "flap" or "diverter" mounted on the (inside) leading edge of the wheel well to deflect the air flow away from the wheel well?

Could they work on the front, or will being so close to the leading edge of the vehicle capture them in a "void" area, rendering them useless?

Will that help or create more problems? If it can help, how measurable will it be? How to measure or prove it?

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Old 04-24-2008, 08:33 PM   #2 (permalink)
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It will probably help, but as Frank said, I wouldn't expect it to be noticeable. If a full rear wheel fairing increases mileage ~2-3%, the benefit from such a small lip will probably blend into the background noise of FE variation. However, remember that small increases add up.

OEM's that actively seek aerodynamics generally set the tires deeper into fenders, lower the gap distance, and fair the trailing edge. The best examples I can think up of are the Honda Insight and VW 1L. If you look carefully, you'll notice how the rear of the wells are faired differently.

Honda Insight


VW 1L


Idealized Open Wheel Well


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Old 04-24-2008, 09:16 PM   #3 (permalink)
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Hi Awillard..,

Did not go to UIUC and major in aeronautics, did you? With a moniker like that, seems you might have spent some time at Willard Airport.

Anyway. Yes, the Prius, and other aero cars typically have a stock diverter in front of the wheel well opening. Its just a piece of plastic that is thick enough not to deflect in the wind, and extends downward and slanted so that the inboard edge is slightly (3/4 of an inch) forward. This would help on your vehicle too. In some pictures on one of these sites, the professional aerodynamicists had taken mud flaps and mounted them on the front edge of the wheel well as a mockup during valuable wind-tunnel time.
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Old 04-25-2008, 09:41 AM   #4 (permalink)
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Nope, never been to Willard Airport, and nope, I didn't major in aeronautics.

I do have mud flaps, front and rear. They help a bunch in the winter when the slushy crud builds up behind the wheels. But, looking down the body, they don't protrude into the outer edge of the body or wheel.

Maybe I'll try extending the leading edge of the wheel well out just a bit. I don't expect massive increases. I'll have to watch during the next rainy road time and see how it affects the spray.
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Old 04-25-2008, 12:08 PM   #5 (permalink)
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Correct me if I'm wrong, but awillard wasn't proposing just "tire spats" - he was asking about taking that concept and extending it up the entire forward part of the wheel arch.

If that's what you're describing, I think it will make things worse, not better.

The "tire spats" that are common in newer cars (and what I think donee is describing) shape airflow approaching the tire tread face.

No manufacturers or efficient prototypes have spats extending significantly up the forward part of the wheel arch - except to get airflow out to the edge of the tire tread.
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Old 04-25-2008, 07:25 PM   #6 (permalink)
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wheel wells

In the eighties,when articles were coming out about the GM and Ford concept cars,journalists were reporting claims from the project aerodynamicists that the volume of the wheel-house itself was a source of drag,and that Ford had gone after it with vengeance,with respect to development of their Probe-series cars.Ford cut to a bare minimum the amount of room in the wheel-well,then they actually added a inner wheel cover which moved with the wheel/tire,to reduce flow interference within the wheel-well.Then they incorporated the flexible urethane membrane which would inhibit airflow into the wheel-house,while still allowing the tire to steer.Looks as if its a good idea to block as much airflow to the wheel area as possible,and any way you can do it.Don't remember any specific numbers for drag reduction being attributed for the mods.I will look again at the article.
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Old 04-25-2008, 09:36 PM   #7 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Correct me if I'm wrong, but awillard wasn't proposing just "tire spats" - he was asking about taking that concept and extending it up the entire forward part of the wheel arch.

If that's what you're describing, I think it will make things worse, not better.

The "tire spats" that are common in newer cars (and what I think donee is describing) shape airflow approaching the tire tread face.

No manufacturers or efficient prototypes have spats extending significantly up the forward part of the wheel arch - except to get airflow out to the edge of the tire tread.
Whoa, I need a picture...This is like a British person speaking to an American: lorries, trucks, bonnets, hoods, petrol, huh?

Let's see if I get this right...

Tire Spats = Fender Skirts
Ranging from this:


to this:


"Tire Spats" = Wheel Splitter/Deflector


Now, what is being proposed?

We need an "Illustrated Guide to Ecomodding"

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Old 04-25-2008, 11:05 PM   #8 (permalink)
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You're right - we do need an illustrated guide!

I call skirts the things in the middle pic and spats the things in the bottom pic (the filename actually has "spats" in it).

Actually the skirts in the middle pic are well past "skirt" status and are verging on full on "bloomers".
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Old 04-25-2008, 11:24 PM   #9 (permalink)
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Quote:
Originally Posted by aerohead View Post
In the eighties,when articles were coming out about the GM and Ford concept cars,journalists were reporting claims from the project aerodynamicists that the volume of the wheel-house itself was a source of drag,and that Ford had gone after it with vengeance,with respect to development of their Probe-series cars.Ford cut to a bare minimum the amount of room in the wheel-well,then they actually added a inner wheel cover which moved with the wheel/tire,to reduce flow interference within the wheel-well.Then they incorporated the flexible urethane membrane which would inhibit airflow into the wheel-house,while still allowing the tire to steer.Looks as if its a good idea to block as much airflow to the wheel area as possible,and any way you can do it.Don't remember any specific numbers for drag reduction being attributed for the mods.I will look again at the article.
Yeah , I remember that as well.
It was sort of a wheel well within a wheel well with the inner one being a really close fit around the tyre.
It seemed to be a promising development but that was the last I heard about it.
Any extra info would be appreciated.

Pete.
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Old 04-25-2008, 11:41 PM   #10 (permalink)
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Unfortunately, it wouldn't work very well for 4 or 5 months of the year where I live ... snow & slush would fill it up and turn to ice.

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