This is a Great Topic. I especially like Vitamin K's post on Monday January 25, 2016, 10:28PM.
I love the Physics of the Pinewood Derby. I enjoy reading everyone's opinion on how to make a block of wood with some plastic wheels go down a hill fast using gravity. I respect everyone, I truly do. Does Physics tell us the wheel knows the difference between a straight nail and a bent nail?
I believe no one can drill a hole for rear wheel alignment and end up with the rear wheels being perfectly parallel to the block of wood. A bent axle will allow any adjustment right up to the point of glueing the nails.