Better response (Bruno J)
Relative to the tire's center, any point along the circumference is moving at 25 mph as given in the problem. The point at the top of the tire is moving forward at 25 mph relative to the center, the point at the tire's bottom along the perfectly flat ground is also moving at 25 mph, but moving backwards relative to the center. The ground is also moving 25 mph backwards relative to the tire's center (as given in the problem). Therefore since both the bottom of the tire and the ground are moving backwards, relative to the tire's center, at 25 mph, then this is the same as the four tires not moving at all relative to the ground at the point they're touching while the car with the four central tire points are moving forward at 25 mph.
I hope this clears up any illusions.