Here's a graph I made a few years ago for my Lexus IS350 to show the performance "change" due to the effective gearing change that occurs when changing the rolling diameter of your tires. The green area shows the increase in torque to the road when going from a tall tire to a short tire. The red area shows the reduction in torque from the same. If you compared the red and green areas that are circled, you can see that they just about cancel each other out.