Tire Deflectors/Spats

[Piwoslaw]

Oooo, that Opel also seems to have small spats in front of the rear tires.

[winkosmosis]

Those look like they're made to deflect air so it doesn't hit the suspension components.

[lunarhighway]

one thing i think to keep in mind when looking at these things is that the dams in themselves are very unaerodynamic shapes, so they will generate a rather wide "wake",

i suppose they don't need to be the full width of the tire to send the air cleanly around it


so when reverse engineering it's best not to assume "bigger is better"

[California98Civic]

Originally Posted by winkosmosis

Those look like they're made to deflect air so it doesn't hit the suspension components.

That's part of what I did with my DIY spats too. I have been meaning to test them.

[SlideWRX]

Originally Posted by piers.singer

It's interesting to note how small the OEM deflectors are compared to some of the DIY jobs on here (if you've acres of coroplast then you might as well use it), maybe the manufacturers are saving material/cost or maybe they don't want the aero parts to impact on the car's styling.

They are also looking at the simplest installation possible.

The larger flaps are also somewhat flexible; they will bend with airflow. I remember the early Ford Contours had flaps in front of the wheels. At the time I had no idea what they were there for.

[PaleMelanesian]

In the week I spent driving a Fiesta, that air dam scraped on at least a dozen driveway/lot entrances. It's a little on the "too low" side.

[PaleMelanesian]

Autospeed - Modifying Under-Car Airflow, Part 2

[Gasoline Fumes]

Originally Posted by Piwoslaw

Oooo, that Opel also seems to have small spats in front of the rear tires.

About half of the cars I looked at had rear tire spats as well. Pretty much all the same back there. Small, flat and straight. Here's the Honda CRZ rear spat:

[Vekke]

I have been doing testing on these flaps a lot lately and they do effect the consumption a lot.

https://www.youtube.com/watch?v=E_OsWefoYjU

https://www.youtube.com/watch?v=NNo0u1BrDxs

I took 10mm off from each flap after this video and consumption got back to 0,1liter higher to 5,5 liters.

Flap width is usually narrower than the tire. Do notice that inner side is wide because it also directs air away from the suspension lower a arms etc. just 10mm changes to shape and size can have measurable impacts.

Tip is that build adjustable flaps in heigth first and get the heigth best setup After that build flaps that you can adjust the width also.
Optimum heigth of the sparts are aroung 40-70mm. And width needs to be about 40mm.

Conserning the A arms the best heigth is around the lowest point af the nearest body structures behind the flaps. Usually lowest point of the body.

You have to be able to test these mods in calm conditions as wind do effect fuel consumption of the results close to 10% and easily 5%. So best is that you try to find level road for 3-5km and test the consumption to both directions. make fast changes and repeat the test. Try to keep measuring speed high so its easier to see the differences. I test usually at 100 km/h, but I will try the method I described and will test at 120 km/h to see better results. To get the smaller differences. I also keep records of the consumption at various points on my test route to see if the consumption changes earlier or later compared to previous setup. That is because in Finland near me is not perfecly level roads so there is up and downhills on the route.

I will also try to test to put angled flap when I have found the best setup if that brings even more gains.

[teoman]

I wonder if the angle has any influence?

Also if they produce some noise one could put a small sawtooth profile on the end.