Chalk test at 28psi cold?

Dynamic load vs static...gvwr is only part of the equation.
OEM tire load rating and psi will give you the load requirement.

Example;
2016 off road
265/70/16/112 @ 30 psi=2,149 lbs
P and ISO metric are derated for use on trucks and suvs by a factor of 1.1. LTs need not be derated.
So...
2,149/1.1=1,954

Now it's just a matter of finding the correct psi to attain that load rating from a particular size tire from the LT load charts. In my case(LT265/75/16), this is 37 psi for a load capacity of 1,986 lbs.

Chalk is 'okay' if you do the complete procedure. Most do about 25% of it...

ETA; LT265/70/16s have a load capacity of 1,820 lbs at 35 psi.

 

They are not P-metric; they are ISO metric.

 

PSI x container(tire) size=total air volume.
Weight is supported by total air volume. PSI in and of iself means nothing. It is a means to an end.
A lot of you are comparing apples and oranges...P to LT, 265 to 285, etc.

 

That is how tires are designed, a volume of air supports the weight and the rating is based on the sidewall's ability to contain it. That's what makes an 'E' an 'E', it can safely be inflated to 80 psi while a 'C' can only see a max of 50 psi.

But there must be more to it than just that. I've always assumed that the heavier sidewalls don't dissipate heat as quickly as a 'C' or passenger car tire, so it's a trade-off to find the right convergence of variables. IOW, an 'E' such as I use run at a lower pressure than intended may flex the sidewall more than the designer intended and might be actually worse at 30 psi than a 'C' or metric.

My reasoning for that is if you look at 35 psi for the LT tires an 'E' usually has a lower rating than a 'C'. For example, both at 35 psi, an index 121 'E' tire can support 1,890 lbs while an index 121 'C' can support 2,535 lbs. But both at their max psi can support 3,195 lbs.

 

Agreed, for load index 110 and range 'C' tires. The Goodyear Duratracs are one example.

ETA: Nevermind, GY doesn't make that size. They are LT265/70R17. Their 265/70R16 are SL-rated with an index of 112.

BFG KO2 in LT265/70R16 are 121/118 and load range 'E', so their ratings are different.

 

I usually go by what's written on the door jam. I'm no Engineer!