The force required to move the car is 500N. Irrespective of the diameter of the wheel the force applied to the end of a torque wrench whose length is the radius of the wheel and tyre and is affixed to a central nut will be 500N Assuming 1kgf to be 10N
The as the torque wrench is extended beyond the radius of the tyre then the force required will reduce because the the moment has increased.
The steps to solving the problem is to regard the moment resisting rotation to be equal to the force need to make the car move x radius of wheel and tyre and be the anticlockwise moment. The clockwise moment applied by the torque wrench at the radius of the wheel and tyre will be equal and opposite to the anticlockwise moment at the point at which motion just commences.
Anti clockwise moment
######= Clockwise moment
Resistant force x wheel radius = Torque wrench force x wheel radius
At this point you can cancel out the wheel radii and demonstrate that:
Resistant force = Torque wrench force
Furthermore since the anticlockwise moment is expressed in Nm and is a constant it is also the torque required to turn the wheel irrespective of the length of the torque wrench seeing that the clockwise moment must also be constant.
What will change is the force applied to the end of the torque wrench as its length changes.
Shorter than wheel radius then the force increases.
Greater than wheel radius then force needed decreases.
End of arguments.