I have "C" load Dura Tracs in 265/70/17. When I had them installed a year ago, the guys at Goodyear told me to run them at around 35 PSIs. Today I got an oil change (not at Goodyear) and they checked the tire pressures and told me I was low so they filled my tires up where they needed to be. I asked how much air they put in and they said "We filled you up to 80, just like the tire says." I about freaked. I wasn't comfortable with this so I told them to take them down to 40 for now. So what should I be running my Dura Tracs at?