Ignoring the reduction in fuel weight as it burns, does the weight on a car's wheels decrease with increasing speeds? If so, by how much and is there a fomula for calculating that? At what speeds does it then become zero?
The weight of the wheels never decrease. If you are observing a car bouncing off the ground at high speed, it's not the weight decreasing, it's the aerodynamic lift due to Bernoulli's principle of pressure difference due to flow speed. But for specificity, the tire might stretch out radially at high rpm due to centrifugal force, but that's extremely negligible in a practical sense.