I'm running a 255 width ST Maxx, so it's not quite apples to apples, but I'll let you know my experience so far. I haven't done the chalk test yet.
The door says 37 PSI with the stock 255's and I decided to start at 35 with the ST Maxx tires. The tires have a bit more of a "domed" or bulging tread surface than some other tires. After a few hundred miles I noticed that the little nubs left from where the mold hairs used to be were completely gone from the center treads. However, the inner and outer tread blocks still have slight nubs (the hairs are gone, but there are still little bumps where they used to be). That makes me think I should go a bit lower, though I don't think it's too bad.
Your tires are wider, so I would think that 32-ish would be a good starting point. That's where I would start. A chalk test would be a good idea, but I don't think you are going to have any issues running 32 or so for a bit until you can get a chalk test done.