Monday, December 5, 2016

Temperature and Tire Pressure

As I started my car to run some errands this weekend, I noticed that my tire pressure was low. Instead of the recommended 30 psi, my tires were around 28 psi. This phenomenon happens every winter when the temperature drops below freezing. This drop in tire pressure with the drop in temperature occurs due to Gay-Lussac’s law. This law explains that if the number of moles and volume of the gas within the tire remain constant, then a change in temperature is directly linked to a change in pressure within the tire. Because temperature is a measurement of kinetic energy of the gas particles within the tire, when the temperature drops, the kinetic energy also drops. A drop in kinetic energy means gas particle collide with the tire’s exterior walls less often and with less force, thus causing a lower overall tire pressure.

Therefore, a drop in temperature by 20 ºC (68 ºF) from the summer to the winter caused about a 2 psi pressure drop in my tires, thus, causing the low tire pressure light on my car to turn on.

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