Cooper Discoverer AT/3 265/70R17 Tire Pressure??

I have a 12’ TRD Sport that came with the stock Dunlop 265/65R17s

Just upgraded and changed size slightly to the Discoverer AT/3 LT265/70R17s — Load Range C, 6-Ply (*Not the 10Ply E Load)

Tire shop inflated these to 39psi.
Cooper Specs show Max PSI = 50.

Since I’m running a slightly different sized tire now, I’m not sure what PSI is recommended for these on my Tacoma. I just have a camper shell; won’t be hauling anything.

Question: What PSI should I run these for everyday use??

What PSI should I be running *and/or can I safely go down to when I’m off-roading in Utah on both slickrock and sand environments without getting a pinch flat?

 

Start with what they have now and do a chalk test then either Inflate or deflate depending on the results of your test results, I have STMaxx and run them at 35psi and it's perfect... good luck