Okay, if you parent your cars to the wheel, I would create a control to act as your driver. Then key the wheel 0-360 degrees and using the driver control, say 0-360 as a new "wheel rotation" attribute.
Also key the cars 0 to negative 360 using the same driver. I think that should work, if that makes sense. Best thing to do is to experiment. If you have a question about how set driven keys works, feel free to ask.