Quote:
Originally Posted by Beau388
This has been discussed many times on this Forum. It is the air in the tires that hold up the coach not the tire its self. The tire is simply an air bladder. Air expands when heated water vapor expands note than air when heated. It is known as Gay-Lussac's pressure temperature law. Using the ideal gas it becomes PV= nRT. If the volume is fixed the equations comes 0= kT/P or P=kT. So pressure is directly proportional to temperature. We will the units out of the equation.
When the tire flexes (remember is is flat on the bottom) it heats up and transfers the heat to the air around it, including that inside the tire. The more the weight on the tire the more heat, the faster you drive the more heat, the sharper the curves the more the heat and the rougher the road the more the tire heats up. So there is no normal, average or acceptable chart as to what the temperature/pressure gain. For me in with a 18,000 lb coach, running 60 mph on asphalt on a 100 F degree day, there is a 24 degree rise when starting at 80 F degree morning at 88 psi. It is true the the inside dual tires heat up more than the outside. This is due to the lack of cool air flowing across the tires. The reason there is a speed limit on most tires is if the tires exceed that speed of a considerable time at rated pressure the tire can overheat and the rubber de-laminate.
It is nice to live beside a chemical engineer who formulated the rubber used in Hoosier racing tires for 30+ years.
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Good info from Beau
I use temperature and have for the past 60 plus years as the easy indicator of what is going on
Given you have to account for direct sunlight as a huge factor
However if you have tires with the same load and one is indicating a much higher temperature check the pressure and load of the axle
corner weights are the best way and then you inflate the tires on that axle to the value required for the heaviest actual weight
If you have to travel on a very hot day on hot asphalt it isn't the day to be pushing the speed as it adds even more heat that has a hard time disipating
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