I'm not going to lie, but I kind of find this thread a little funny.
Yes, going to a lighter wheel should technically make your car faster. How much? It depends on what you have on there now vs what you plan on putting on. By decreasing weight, you're decreasing the amount of inertia required to rotate the wheel (i.e. less power to rotate). But in another sense you can also think of it as an aid to steering as now you have less mass to rotate side-to-side.
If you want to have a fun math exercise and a very rough ballpark as to how much less energy is required to spin your wheel, treat the wheel and tires as cylinders. For the wheel, the energy needed to rotate it is Iz = (m*r^2)/2. Where m is the mass of the wheel and r is the radius. For the tire, Iz = (m/2)*(R^2+r^2). m is the mass of the tire, R is the overall diameter of the tire, and r is the inner diameter of the tire (or just use the diameter of the wheel). Add the two together and you'll see the total energy. Do it for both setups and take [(IzOld/IzNew) - 1]*100% to find out how much more energy your old setup takes to spin than your new setup.
Wiki for equations:
https://en.wikipedia.org/wiki/List_of_moments_of_inertiaIf you look at the formula, you're going to notice that a change in radius of the wheel or tire is going to have a larger effect than changing the weight of the wheel. The radius is an exponential. Also, if you think about it, a tire weighs about about the same (+/- 15% depending on wheel and tire setup) of what the wheel weighs. So, technically going to a smaller or lighter tire will likely have more of an effect than a lighter wheel since all of the mass of a tire is outside the perimeter of the wheel (i.e. farther from the center of rotation). Most people have the problem; however, with traction going to a smaller tire. As mentioned before, the rears of a drag car are fat and meaty to get as much traction as possible (notice that a lot of people use lightweight wheels though), but on the fronts, they use pie cutters as they're easier to rotate about its axis.
