Undertray skirts /tyres dirty air

[John Mcrain88]

I am interseted what is best solution to solve dirty air at front and beck tyers,to minimized negative effect on undertray/diffusser.

Do I need to put skirts aorund tyres too,what is best way to desing this?

[coaster]

Road cars build pressure under the wheel arch lifting the car, bleeding the pressure out gives a good result example; louvres, holes or ducts.