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.
CarsDirect.com recommends cleaning the fuel intake, throttle body or the carburetor, as well as readjusting components to manufacturer specifications to eliminate vibration caused by the fuel intake system. Damaged or broken motor mounts are arguably the most serious cause of engine vibration.