Originally Posted by jtownstumpjumper
Setting tire pressure at 80 psi in 50 degree weather on our first trip of the season a few weeks ago turns out to be a little more when you start out in 80 degree weather as occurred with us this week....noticed immediately they were reading more like 85-86 psi and after about 2-3 hours on the road we were reading 95 psi, very near my upper alarm limit...I know those tires can stand much higher psi's but still I stopped and made adjustments just for the ease of mind....the TST system is well worth the price as far as I'm concerned.
If by "adjustment" you mean you let air out of your tires that is the wrong
thing to do. Tires should be set to the "cold inflation pressure" selected for your RV when the tires are cold.
Cold in this case means not driven more than 1 mile in previous couple hours or in direct sunlight in previous couple hours.
Tire pressure will change about 2% for every change in tire temperature of 10°F and tires are designed to handle this for tires that are not overloaded or driven at speeds higher than their rating.
I have covered how to learn the proper inflation pressure and how to learn the desired cold inflation pressure a number of times on my blog. Some posts even show the math involved.
I really do not understand why some feel they need to establish an upper pressure limit. The important limits are Low pressure (anything below the inflation needed to support the measured tire loading. and the upper temperature limit which is about 155°F for most TPMS from the factory.
Even on a 100° day an increase to 150F would only translate to about 10 to 15% rise in pressure and unless the tire has been damaged or improperly repaired ti should be able to handle a +15% in pressure.
Also you would need sustained speed
at max rated speed and at or above max rated load for hours to raise the tire temp to 150 at the external sensor.