[CorollaMaster]

toomuch - thanks again for the post, that was a good article and a neat site!

LostCause - I think the sidewall flex would be another reason to pick a larger diameter rim and slimmer tires. There is less sidewall to flex, and as a result probably a lower contact surface as well. The main benefit though is the displacement of all the weight to the outside of the wheel, that has to be another factor of rolling resistance.

I also wanted to respond to your comment about the contact patch. The contact patch is relevant because its the amount of area that the car is putting energy into to make it move. It's like trying to run in the summer with snow shoes versus running with just sneakers. The sneakers have a smaller surface area and allow you to focus the energy into moving you forward on a smaller area. With the snow shoes there is a larger surface area and the force you apply is displaced accordingly so it takes more energy to move as fast as you would in sneakers.

I guess the problem is that we are not talking just about rolling, we're mainly talking about how much gas is used going from the engine to the tires, and if you have a smaller contact patch you will end up using less.