I was recently asked "What do you recommend for high pressure setting with a TPMS?"
The person said after driving about 50 miles in 92°F weather he was seeing 148°F on his right front and the left front went to 136°F on his Class A RV. His tire pressure monitoring system (TPMS) has a setting of 158°F for high temp. He wants to know; At what tire temperature should he be concerned when driving?
A couple of quick points.
If the TPMS is one of those that screws onto the end of the valve, then it is reading lower than the hottest part of the tire. If he has extension hose on the dual then the temp reading is even lower. I have tried to find a TPMS manufacturer that has data on the temperature difference but so far either they do not answer my email or they haven't bothered to do a test.
My information indicates that a properly loaded and inflated Class-A tire will probably see 140°F to 170°F operating temperature and these temperatures are OK as the tire is designed for this temperature range.
If you have actual side to side weight and know you are not overloaded, you may see temperatures in the 140 - 170°F range. If you see higher then I would be a bit concerned and want to know why.
Setting your TPMS Max warning temp to 158°F sounds reasonable to me.