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.
Steering vibration is almost always caused by the tires/wheels. Either your wheels are out of balance or one or both of your tires is defective. There could be a broken belt in the tire that is causing the vibration. If you don't want to take your vehicle to a tire store right away, you can check by reversing tires front to back.