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.
This wobble will cause the tire to wear improperly and probably show up as a vibration as well. Bent Wheels: A bent wheel, in addition to probably causing a vibration in the car, will also affect the wear on it's tire and can even affect the wear on the other tires as well.