Thanks, munks, you're very kind.
Well, I would say that indentation and tyre pressure are vaguely related, then.
I would also say that tyre pressure depends mainly:
- on the tensile strength of the tyre plies and rubber and
- on the amount of air inside
- plus dynamic effects (the whole thing is under centripetal force when spinning)
As we discussed earlier, a tyre does not support itself on the floor directly
through the pressure of air. It is not a balloon. It is a more complicated structure.A tyre does not push against the floor: the axle of the car hangs from the "upper" tread.
The rim pushes down the orange bead. This bead pulls the walls in green. The walls are suspended from the top tread in red. This top part of the tread, which is the structural element in a wheel, I compare with an arch. This arch is made rigid by the pressure inside the tire
. Like this (sorry for the copy/paste).
So, that's the interaction, between tread and air (air making the tread rigid), that controls the pressure inside. If the pressure is not large enough to make the tread rigid, then the pneumatic would "need" additional pressure inside to recover static equilibrium. The tyre develops this pressure by diminishing its volume, ergo, more air pressure (or indentation).
It's not the weight of the vehicle divided by the area of the contact patch.
I think that's the reason why the guy in the link posted graciously by hardingfv32 declares himself to be confused by actual pressure measurements. He's trying to correlate them somehow with contact patch size. Good luck with that!