Check out this excellent article on how your vehicle's Unsprung Weight and Rotational Inertia affect the handling and ride quality of your ride: http://www.nissanperformancemag.com/february02/oz.shtml
Suddenly, my oh so stock 15 inch OEM wheels and tires don't suck as bad as I thought... :P
(yeah, I know, they still suck hind teat!)
For years, I have been looking at those big ass trucks from Dodge and others with those fat ass wheels and knobby tires that must take gobs of torque to turn!
Just image a lowly, torque anemic v-tech engine busting a nut trying to turn 18, 19 or 20 inch wheels, even if they are light weight designs...