What I concluded by adminstrative research in time, is that advice pressure is determined for 18/20degr C./ 65/68 degr F.
And its all done to not overheat the tires.
Cold pressure is when inside tire temp = outside tire temp, that simple.
when outside tire temp (Ambiënt)is colder then the temp I gave above, the pressure drops in tire, so more deflection of tire> more heatproduction.
But also more cooling down of tire, because temperature differences are higher.
for fuel saving you can then give tire a same deflection as for that 65 degr F , by giving it the advice pressure at that colder temp.
But for savety its not needed.
The other way around, when its hotter then 65 degr F, pressure rises> lesser deflection > lesser heatproduction, but also cooling down is lesser because of the lesser temperature differences.
so when hotter outside dont lower your cold pressure to adviced, you then will get more deflection so more heatproduction, so hotter rubber when driving.
My idea is that between about 20 degr F and 100 degr F outside tire temp, the cooling down of tire and warming up is in balance so not any part of the rubber of tire goes above the temp at wich it hardens and crackes in next bendings/deflections.
so when you measure your morning pressure, also see what ambiënt temp it is at that moment.
There are rules of tumb , of every 10 degrees different 1 psi diferent, but this only goes in a sertain range of temp and pressure, better would be a percentage rising of lowering for every 10 degrees, wich would go for high and low pressure.
Will give a list I made with spreadsheet, for the higher pressures, because this is the Clas A motorhome part so high pressures used.
