Select one good wheel. Spin it on an axle and record the time. Repeat several times. With the same wheel, test another axle Repeat for as many axles as you have or until you reach a point of diminishing returns. Select the 4 fastest.
Lighter wheels are faster .
Anything you can do to make the wheels lighter will increase the speed of a PWD car. There was none. The car was verrrry slow. Material can be removed from the tread, like the wheels in my catalog. It can be removed from the inside cavity of the wheel.