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.
Excessive wear on the tires occurs when the tires are unbalanced. Unbalanced tires cause increased stress on a specific area of the tire. These stresses combine with the uneven motion to cause vibration, which leads to excessive wear and a greater risk of deflation.