The answer is (a): the spring scale will still read about 8 Newtons, as seen in an mpeg video by clicking your mouse on the photograph below.
According to the "laws of friction," the frictional force between two surfaces with the same types of materials is independent of contact area, and dependent only on the normal force.. This is very nearly the case here; the frictional force is only slightly higher when the smaller contact area is used.
If this is so, why do people like wider tires, that have more contact area with the road?
