You can put this solution on YOUR website! If the weight(W) of a car is directly proportional to the tire's circumference(C):
(W)/(C) = (W)/(C)
2 ton or 4000 lb car with a 32 inch circumference
Y/X = 4000/32
Y = 125X
Where the x-axis is the circumference of the tire
Where the y-axis is the pounds of the tire