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.
Warped brake rotors are the most common cause of braking vibrations. In addition to a vibration, warped rotors may cause your calipers not to release completely and lead to uneven brake pad wear that will cause your brake pads to need to be replaced sooner than they should.