To capture this biker and give the image a sense of motion I used a slow shutter speed (1/90th) of a second. I panned as i took the shot, moving my body from the waist up, tracking the biker with my camera. Because my camera followed the subject, the Navy biker is in sharp focus (that is also where my focus point was). Because the shutter speed was slow, the other parts of the image are blurred because of the camera motion. The slow shutter speed also blurred the bike tires and spokes a lot and blurred the ends of the main subject slightly.

There is no one speed that you can use to get this effect. You have to experiment to get the right speed. The correct speed depends on the speed of the subject, the distance the subject is from you, and the direction the subject is moving.