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.
Unbalanced tires can create a small hum, a slight shake or a significant vibration that makes driving the vehicle unpleasant. Steering wheel and seat vibration is a frequent sign of unbalanced tires. This type of vibration is distinct and gives information about which tire is unbalanced. When the front tires are unbalanced, the vibration is experienced in the driver's hands through the steering wheel. When the rear tires are unbalanced, passengers feel shaking in the seats. 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.