Tire pressures during temperature swings
I see a 3-4 PSI rise in my Ram 2500 tires from a cold start to highway driving after 30 minutes. During the day, if starting off from a cold location, to the hottest destination, do you account for...
Forum Discussion
GordonThree wrote:
So no problems if I set the cold pressure at 15F ambient and later in the day it's 50F ambient? Often see huge swings like that around spring.
while 35F may seem like a big temp swing, it really isn't relative to pressure changes. First convert to Centigrade. it's a 20C delta.
Next, boyles law states PV=rT. tire volume remains the same, r doesn't change, so pressure is related to temperature change in a linear fashion, but 15F is about 260 degrees Kelvin, so we are looking at a 20 degree change relative to 260Kelvin. about a 5% change in pressure. so given say a 60psi at 15F changes to maybe 63pis at 50F. not enough to normally worry about.
Now what can also have a noticeable effect on pressure is how much water is in the air in the tire. as water heats up and vaporizes, it increases tire pressure as well.
Now if it's a racing situation, another story for caring about PSI changes. That's why most racing teams use dry nitrogen. They don't need to worry about pressure changes due to water vapor changes and they have a known defined characterized gas.
But in the end, for us travelers, check and adjust your pressure with the tires cold and don't worry about it during the day. Tire mfg have already accounted for temp rise effects in the tire design.
