Wow, didn't know anybody noticed this thread.
First, let me repeat. OZ RACING have been using hollow wheels on the SAUBER F1 CAR for several years!
Now, you can argue the benefits of this design as much as you want, but unless you know specific air volume measurements you cannot actually get a number to determine the change in tire spring rate. However, I am confident there will be a change in tire characteristics if you change the internal air volume. How much and to what benefit is hard to say, but OZ Racing developed wheels for that purpose, and they have been used/developed/updated for 4+ years, so they must do something beneficial
Personally, I think the 2011 Sauber is doing well in part because of these wheels and their interaction with they VERY SENSITIVE Pirelli tires. The air volume difference may not have made a big influence in past seasons, but it seems likely that the Pirelli's are a very different animal.
Also, I've been hearing that the RB7 has updated its wheels for Barcelona, and they are sponsored by OZ Racing, so interesting if we see them switch to the hollow section wheels.
Oh yeah, for anybody having difficulty imagining why the air volume would effect the spring rate. Without getting overly technical (I can if we need to), the cause is due to the Ideal Gas equation (pressure is inversely proportional to volume), the effect is a NON-LINEAR SPRING RATE. For example, due to the non-linearity, a 20% increase in air volume could have an 80% change in tire characteristics.
Ideal Gas Isotherms
Spring rate change
I love to love Senna.