A British thermal unit (Btu) is a standard unit of energy that is used in the United States and sometimes in the U.K.
There is another defect in tires that can cause a vibration called loaded road force variance. The tires and pass a visual inspection, a radial and lateral runout test, be perfectly balanced, but still cause a vibration. This is due to the internal defects in the tire.
Tire balance or bent rim, alignment can't cause a vibration directly. It can wear the tires to the point that they vibrate, but the actual alignment won't make it shake. Edit: Also a bad tire can cause this. e.g.: out of round tire, but not unbalanced. #3 May 6, 2004.