hmmmmm . . . . I'll have to take a look at that, don't have time right now, because I have been musing about the mysteries of contact patch lately

but I thought, in theory, the area of the contact patch only depends on the weight of the car and the tire pressure, because

total contact area in^2 = (weight of car lb.) / (tire pressure lb/in^2)

 

I'd have to pull the formulas and math for that, but if we are talking about the same thing: that holds true for a given size tire, but does not account for different sizes.