What makes a winning can in a high school soup can race?

[sugarfreeky22]

my class is doing the typical soup cna race this friday, and i am in desperate need of suggestions! we have to come up with the fastest and slowest cans, both stock and modified. Modified can include basically any addition or alteration to the can excepting the addition of motors

 

[jim mcnamara]

fast = reduced friction, solid contact with the race track, perfectly round wheels, lower center of gravity, increased mass (or density like adding lead weights)

slow = increased friction, bad wheel train, lighter weight