If more air volume increases weight capacity, would I be doing any harm by having a Cold Air Pressure of 85 PSI in my tires versus the tire sidewall 80 PSI recommendation? Especially when temps are cooler?
That maybe a bad assumption. Maybe our tire engineers Tireman9 or CapriRacer can give you a answer on LT tires.
We do know that a P tires load capacity stops at 35 psi even though the tire may have a 44 to 51 psi rating.
What I do know is a LT E tire at 80 psi can reach 94 psi with a load in hot weather and at interstate speeds. Now the tire is pumped to 85 psi can have the tire at 99 psi. Doesn't sound like a good idea.
Cummins makes a good point about your trailer and LT E tires.
Montana Big Sky 3670 models have GVWRs in the 14k-15k range and came with a 3500 lb ST tire. Sounds like you or some one put a under capacity replacement tire on your '05 36'-38' trailer.
The sidewall bulge at the bottom indicates a over loaded tire/under inflated tire or the infamous ST tire sidewall bulge.