Ok, before I begin, I have done a search on this forum and read all relative posts on tire pressures as well as google'd it for more information. So after reading all that and the various opinions on pressure here is my question. As some of you are aware I recently bought new tires. They are 10 ply with a max PSI of 80. I asked the guys at the Firestone dealership what pressure I should stick with for normal driving and they said just follow what's on the door jam and pump it up a "few notches" for hauling/towing. Door jam says for P265/70/17 35 PSI for all tires. These are LT265/70/17. So I was thinking maybe I should have it a bit higher. I did the chalk test, and I get an even white chalk line across the entire width of the tire, so I'm confident that 35 PSI is sufficient. My question is in regards to towing. A few people I know have used a rule of thumb of +10 PSI when hauling/towing. Is this a good rule to follow or should it be more? That would only put the tire at 45 PSI, just barely half of what it's rated for which seems low to me, but I also thought the 35 PSI would be low and it seems to be a good number. I'm aware I could do the chalk test when everything is all loaded up which is fine in summer, but when it's -40C out in the winter and I just finished loading a moving trailer as well as my truck up with everything from my apartment I'm really not going to feel like marking chalk on the ground behind all 4 tires and moving the truck 6-12 inches and then f***ing around with adding/letting off tire pressure. So +10 PSI "rule" or should I do something safer like fill it 60-65 PSI?