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.
The common type of vibration is mainly felt through the steering wheel of the car as it accelerates, and it is a very dangerous condition because it can cause unstable conditions that can lead to loss of control especially when avoiding a collision or making a sudden turn.