Summarize:

Draw a line of hot glue around the clear, plastic circle at the center of a CD. Quickly press the top of the wooden spool into it. Make sure that it is centered. Repeat this step for the other three CDs.  You can use old, scratched up CDs or blank ones. Hot glue sets up quickly, so work one spool and CD at a time. The button needs to be big enough to cover the hole in the middle of the CD. Use a standard 2- or 4-hole button, not a shank button with a loop on the end. The button will cover the hole and keep the wheels in place. If you can't find any buttons, cut circles out of thin cardboard, and use those instead. Slide two rubber bands onto your first wheel so that they make an X shape on the front. Repeat this step for the other three wheels. This will give your wheels some traction. The rubber bands should be wrapped tightly around the wheels. You may need to wrap them more than once. These will go between the wheels and the cardboard tube. Place the wheels onto the ends of the dowels. Make sure that the cardboard tube is centered, then measure the gap between the spool and the cardboard tube. Cut a straw down to fit those measurements. You will need four pieces total.  Your first/front set of straws should be about 1-inch (2.54-centimeter) long. Your second/back set of straws should be about 2¼-inch (5.71-centimeter) long. You can use plastic or paper straws. Consider using a color that matches your car. Take the wheels off of the dowels first. Place the short stoppers onto the short dowel, and the long stoppers onto the long dowel. Place the wheels back onto the dowels and test the fit. If the stoppers are too long, take everything off and trim them down again. Once you are happy with the fit, take the wheels off and add a drop of white craft glue into each spool. Place the wheels back onto the axles, and let the glue dry. The wheels should fit snugly onto the axles. If they are too loose, wrap some masking tape around the end of the dowel to thicken it.
Hot glue a  1-inch (2.54-centimeter) wooden spool to the back of each CD. Hot glue a button to the front of each CD. Wrap some rubber bands around the wheels. Cut some straws down to make the stoppers. Add the stoppers between the wheels and the cardboard tube. Attach the wheels.