Quote Originally Posted by camoit View Post
It's true,,, People don't like there tooshy to be numb when they get out of the truck. It's the pins and needles when the feeling comes back they can't stand. It's not polite to scratch your self in public.
Pretty good (and interesting) Wikipedia article describing the 2nd order harmonics created in an inline 4-cylinder engine.

I feel stupid that it never crossed my mind that harmonics would be generated, and that balance shafts are actually a work of genius, not a worthless sub-system to be removed. Live and learn (especially now that there's not much time left for either :-))

http://en.wikipedia.org/wiki/Inline-four_engine