Experimenting with some different tires and wheels. Turns out that the white sweep wheels are much stiffer than the yellow sweep wheels.
Also, the white sweep wheels are larger in diameter than the tamiya swift wheels, which causes the tread surface of the slicks to be concave....not good. The m-grips are flat on the sweep wheels, and nicely rounded on the tamiya wheels. The tamiya wheels are also wider, stiffer, but slightly heavier.