It's off to the races. Set your car on the floor, rubber band side down. What happens when you let your car go? When we made ours, our wheels didn't always turn freely. If this happens to you, make sure the catch isn't hitting the cardboard when the axle spins. Also, check to make sure the rubber band isn't jamming itself against the cardboard. We found that wrapping the rubber band more carefully usually solved the problem, but you can also create more space for the rubber band by making the notch just a little wider.