do you need smooth wheels if you have skirts

[moonmonkey]

im building rear skirts for my echo, maybe fronts, it has the stock toyota steel rims,that in mind do i need to also buy smoothies or install pizzia pans, or would that be a waste. I have heard that the rims might pick up air and blow it into the wheelwells but these rims dont look like a very effecint fan.

[NeilBlanchard]

The wheel are still "churning" air inside the wheel well -- the Hucho aerodynamic book talks about having close fitting inner fenders to reduce drag of the overall vehicle.

So, with solid covers, the air cannot pass through the wheel, and so the air gets churned less behind the skirt. And the part of the wheel that protrudes below the skirt is also helped.

[tasdrouille]

Neil is right. Once you have skirts, for best results you still need to isolate each side of the wheel so there's no flow though.

[aerohead]

Ditto.