Originally Posted by
dminor
Wait a minute . . . if the contact patch is longer, then, for the same width of a given tire at the same psi, wouldn't it stand to reason that the contact patch would be physically larger in sq in?
Well... do the math. For a given tire pressure in pounds per square inch, the area A of the contact patch in square inches is the weight W on the tire divided by the pressure:
A = W / P
This does not depend on the shape of the tire. So, as long as P and W stay the same, if you make the contact patch longer, you also have to make it narrower, so that the area stays the same too.
A 700x32 tire at 60 psi will have exactly the same size (i.e. surface area) contact patch as a 26x2.1 tire at 60 psi, or a 24x1.75 tire at 60 psi.