Do wheel skirts really work?

[MetroMPG]

Good points, Rick. Cd figures do represent a head-on calculation. Cars with the same Cd & A values (but different shapes / aero detailing) could see different results in crosswinds.

[MetroMPG]

Cool.

Our wheels will be flush with the fairing

So your front wheels will be exposed & disc covered? GoOne style?

This sounds like a really fun project.

[trebuchet03]

Originally Posted by MetroMPG

So your front wheels will be exposed & disc covered? GoOne style?

Yep. Minus the suspension :P


mind you, this is not the most up to date version - but the overall shape has stayed the same.


I really wish I had the money -- I'd buy a model of my car, build a water tunnel (which can be done cheaply with decent flow visualization results) and test :P You can even tackle the cross wind scenarios I didn't even think of those situations until now :P

[MetroMPG]

So just drive really, really fast and drag the apparent cross-wind up closer to on the nose.

[jmandidly]

has anyone tried using gurney flaps instead of wheel covers, I have been thinking of trying them on my car

[zpiloto]

It's been a cold rain all day today. I noticed looking at the cars as I was driving around that there is significantly more spray from the front then the rear wheels. Which would make me think that some kinda of coverage on the front would decrease drag more than on the aft wheels. Has anyone run across any data that reflects that?

[CO ZX2]

Originally Posted by zpiloto

It's been a cold rain all day today. I noticed looking at the cars as I was driving around that there is significantly more spray from the front then the rear wheels. Which would make me think that some kinda of coverage on the front would decrease drag more than on the aft wheels. Has anyone run across any data that reflects that?

Here is an aerodynamic drag chart I saved from Autospeed magazine. Toecutter says it may be Volvo but it should be a decent guide for most modern cars. Front wheel drag percentage appears to be about double the percentage of rear wheel drag. CO ZX2

[lunarhighway]

front wheels add to the frontal area while rear wheels don't... i'm sure this is over simplified but still... also front wheels will take a lot of dirt and water of the road while the rear wheels will follow in this "clean" trail.

is would be very interesting to learn how much drag is associated with the fronts, sides, wells and spinning motion of the wheel.

most cars i see seem to have something in front of the wheels rather than beside them which makes me wonder if this area isn't more important? apparently car makers rather invest in plastic in front of the wheels (wich has very little impact on the cars appearance) than in plastic besides them (wich alters their looks a lot)

[Bill in Houston]

I wonder if that is because the road has more water on it when the front wheel runs over it than when the rear does? But I have seen what you are talking about. It does seem like there is a lot more air whipping around in that front wheel well than the rear one.

[Dynamically Aero]

In this article about the Nissan P35 mention is made of the R89C. There are a number of interesting photos of the P35, including those accompanying both Part 1 and Part 2 of the story. WARNING! Going to other pages at Mulsanne's Corner may result in large periods of missing time. You've been warned.

As for the outlets in front of the rear wheels of the R89C, the upper one is to expel air from the intercooler, and the lower one is for the turbo's exhaust and wastegate. These can be seen in this small and this larger photo of a model of the R89C. This is a thread covering the building of an amazing R89C model.

For an example of another Group C car with a similar setup, see this photo of a model of a Porsche 956.

To see how a street version of the 956 routed things differently, this model shows the exhaust exiting out the back, most likely due to a law prohibiting side outlets.

Speaking of exhaust, in the P35 article there is this bit of information regarding underbody airflow: "Exhaust activation of the underwing had been used on Suzuka?s previous Nissan GTP cars, and it was also adopted for the P35." Here is the link to photos of the exhaust holes referred to in the above quote. Interesting, isn't it?

For photos of more models of cars which competed at Le Mans, go here.

The Jaguar XJR-9 is another race car which used rear wheel skirts/fairings. To see what else competed against it and the R89C in 1989, click here.