FYI: my tires are load range "E"; max load at 80 psi = 3500 lbs.
To determine safe pressure I use a reduced pressure/vs load formula which returns the same result "FI" got from Denman.
Say; N = new max load at reduced pressure
M = max load at max press
Pm = max pressure
Pr = reduced pressure,
then
N = M*(Pm +Pr)/2*Pm
Plug in M = 3500, Pr = 70 psi, Pm = 80 psi and :
N = 3500*[(80+70)/2*80] =
3280 Lbs. (I run my tires at 70 psi, cold). With four tires I can carry 13,000 lbs, but am usually under 11,000 lbs.
In the Denman case that's:
N = 2800*[(80+70)/2*80] =
2625 Lbs (close to the 2600 lbs. they advised)
The formula is, I think, ok as long as the pressure reduction doesn't exceed 20%. Beyond that it predicts load capacity above real world. Also one would really not want to reduce pressure that much anyway.
Just my $0.02 worth
.
Denny_A