Hopefully someone can give me some insight I've never done a rolling shot where the car is clear and the back ground is still in motion (blurred) and Ive had my go pro hero3 for a while just wasn't sure what setting to use . Thanks
You need a longer exposure setting, not sure that is possible with a GoPro. Depending on your speed and time of day(longer when darker) 1/4 or 1/2 second will get you a nice blur.
A lot of those shots you see are either rig shots or longer exposure shots like grimace mentioned but as far as I know the GoPro doesnt have that specific functionality as you need to set shutter speed/aperture. The car also doesnt move fast at all, its actually going at a crawl and the shutter is open for a good few seconds and the rig is processed out.
However! What I would reccomend trying is, use one of those "selfie sticks" and get someone to drive your car, and hop into someone elses car and snap a few photos with your GoPro low and close to the vehicle. I bet you can get a shot very similar to a rig shot that way.