1. (Units) a unit of heat in the fps system equal to the quantity of heat required to raise the temperature of 1 pound of water by 1Â°F. 1 British thermal unit is equivalent to 1055.06 joules or 251.997 calories.
Quick Answer. A major factor that usually causes tire noise is the air chamber inside the tire. The large void that is filled with air acts as a giant resonance chamber. Thus, the tires are something like donut-shaped drums that generate a low-frequency hum when tires are rolling.
Wheel Balance: Out-of-balancetires will cause a car to vibrate at certain speeds, usually between 50 and 70 mph. A tireis out of balance when one section of the tire is heavier than the others. One ounce ofimbalance on a front tire is enough to cause a noticeable vibration in the steering wheel at about 60mph. To balance a wheel, the technician will mount it on a balancing machine which spinsthe wheel to locate the heavier part.