[jshadeck]

For those who dont understand what the purpose of the design is, they are designed to tuck away below a certain mph (usually below 60 or so) as all a spoiler does at those speeds is cause drag and slow u down. But above x mph it raises (some adjust more so as speed increases) to provide downforce to counter act the natural rear end lift most street cars are prone to.

Edit: as seen on porsches, mclarens, bugattis to name a few