1) In a circular motion, the angular displacement 
is given by
where S is the arc length and r is the radius. The problem says that the truck drove for 2600 m, so this corresponds to the total arc length covered by the tire:
. Using the information about the radius, 
, we find the total angular displacement:
2) If we put larger tires, with radius
, the angular displacement will be smaller. We can see this by using the same formula. In fact, this time we have:
where S is the arc length and r is the radius. The problem says that the truck drove for 2600 m, so this corresponds to the total arc length covered by the tire:
2) If we put larger tires, with radius