Sometimes at the Track the Tires will move on the wheels especially if you are pushing it. This can make the Tires go out of balance and make the ride become rough. Here is an example from last weekend at Buttonwillow Raceway after eight sessions.  Left rear side. The yellow line was originally lined up with the Valve stem.

Mine definitely moved, started vibrating on the straights. It usually happens if you are running sticky tires like Hoosiers or slicks, not so much with street tires but still possible. 

You guys just drive too fast. This never happens to me