Rotating mass isn't just about the tire. Also think about the wheels. I also have a Free Spirit & have been using it as a daily rider since 2003. I do like the snowflakes, but if I was really going for faster acceleration, I'd change to ally wheels n spokes. Drilling the sprockets won't have much effect on MOI (moment of inertia), but may help with over all weight of the bike. Lots to be read in MC magazines about that subject.(MOI) Over all lightness of a bike WILL have a measurable difference in acceleration. The Hutchinsons are one of the stickyest tires out there & I'm sure you can drag a knee if you're wearing the proper gear, although the Pierelli 16" tire won the first Polini cup, however that could just as well been rider ability. I could go on & on, but just have fun with your Free Spirit like I have for the last 10 years.