Tips for a fast car design? I'm planning out the design for a 12'' car that I will be racing for my science class. There can be no type of motor whatsoever--the "track" will begin at an incline, with only gravity propelling the car forward. Also, the maximum mass is 300 grams. Any advice on how I could make it go fast, in terms of its design?

You want big wheels with a reasonably hard surface - avoid soft rubber. Low centre of gravity. Make sure it steers straight. And use the full weight allowance.