Another one of those "why didn't I think of that?" things:

First introduced last year, the Tweel sports a flexible spoke/wheel design that replaces the need for air pressure, deforming to absorb shocks. See it in action after the jump.

“…vertical stiffness (which primarily affects ride comfort) and lateral stiffness (which affects handling and cornering) can both be optimised, pushing the performance envelope in these applications and enabling new performances not possible for current inflated tires.”

~ Techeblog: Muchelin’s Airless Tires