I read lots of education around how the high pressure for a MTB tire is bad and how the low pressure is very good for the rolling resistance. I feel puzzled by these talks because they seem contradicting my experience. From the other side, I have not done any precise measurements.
Has anybody actually measured the rolling resistance as a function of tire pressure, using a MTB-like tire (so wider than 2" or about) and the MTB pressure range (somewhat between 1.8 till 4.0 bar I think), I mean experimentally? Would it be possible to see such a table or chart? It would be interesting to know if these low pressure recommendations are some contra-intuitive reality or just an urban legend, pushed by desire to sell easier generally good (soft maybe) but not pressure-tolerant tires as "high end". I understand that low pressure likely results more grip and may be better on something like sand. This question is about the rolling resistance on a reasonably hard surface, however.
There is a good chart here but it starts at 4.1 bar. This is already more than a typical MTB tire is designed to hold so does not look usable for my case. It declines till 7 bar is reached that looks for me above the extreme, only then starts growing again.
Simply "manufacturer recommendations" are out of scope of this question, unless they do provide the measurement data covering the relatively wide range.