NASCAR Racing: maintaining pace under caution, robby gordon, pace car

Question
NASCAR officials stated that Biffle maintained pace yesterday to win @ Kansas, but that he did not have to keep up with the pace car.  I don't understand.  I know that there is no passing under caution. You must, however, maintain a certain speed, or pace, to stay out on the track (just ask Robby Gordon).  What does it mean to maintain pace if the pace car has nothing to do with it?

Answer
The rule states that you must maintain a reasonable speed, not pace speed. Biffle coasted to the win doing about 40 mph while the field was going by at about 50. Nascar sees that as reasonable. robby Gordon was spun out at Montreal and did not maintain a reasonable speed cause he spun to a stop.