This week on Car Talk, Click and Clack delve deep into scientific inquiry on the expanding American rump. The fruits of their labor? A new way to measure the human derriere. Presenting... the "Pinkwater," after Tom and Ray's pal, his rotundity, Daniel Pinkwater. Also, Kathleen has a moral, ethical and economic dilemma: to buy a SUV or buck the big car trend? And Matthew is struggling with his car washing technique. He's striving for spotless perfection on his parent's Voyager. Could the Shawalla be the answer to all of his car-cleansing woes? All this and much more, this week on Car Talk.