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.
For example, at freeway speeds, an out of balance wheel can be slamming into the road 14 times a second. That's annoying and can cause your tires to wear out more quickly. If a front wheel's out of balance you'll feel the vibration through the steering wheel. When it's a rear tire, you'll feel the vibration through your seat.