I know I have read the old posts about PSI. I just bought Goodyear Weatherready tires and they say 51 PSI!! Wow huge difference from my Michelins, and the door 30 PSI label. Can I get away with more air on this tire type?
Tire sidewall has the Maximum Cold Inflation Pressure molded into the sidewall. This is for basic reference and is used for your Bonneville Salt Flats unlimited speed runs only.
As posted, the driver's door sticker gives the tested and recommended cold inflation pressures for the car - regardless of tire type or speed rating. An anal, conscientious driver will use several different cold inflation pressures over time to develop the "best" overall pressures for that car, tires, driving habits, and fuel economy. The pressure settled on will not be more than 4 or 5 pounds different from those recommended on the door sticker.
"Cold" = ambient temp out of the sun before driving one mile after an overnight rest. Pressures increase as the tires heat up from driving and different conditions - it's all factored into the recommended cold inflation pressures.
Look at the over-inflation tire - your 51 psi (cold) would do that in a big hurry.
Those images are an excellent example of improper tire wear. One very important wear pattern is left out, however. I have been involved with tires and auto maintenance for over 30 years, and it still amazes me that people do not rotate their tires often enough. It looks similar to the Cup Wear shown, but it is heel and toe wear on the individual tread block. Choppy tire wear. It is a direct result of not rotating tires often enough. Rotate them every 5,000 or so miles people, and do it the way the manufacturer recommends. When you buy a $1,000 set of tires, and 10,000 miles later they have that choppy pattern, it is NOT the tire's fault, it is yours silly.
Basic rule is, FWD cars, the front tires go straight back, the rears cross sides to the front. RWD cars are the opposite, the rears go straight forward, fronts cross sides to the back. An AWD STS I would rotate like a RWD car since it is a rear wheel biased system. An AWD car like a Subaru or Audi, rotate those like a FWD car, since their system is biased to put more torque to the front tires. You can rotate staggered fitment tires like the STS sport, just do it right to left. This will almost always eliminate the choppy wear pattern.
The air pressure recommendations above are spot on, about cold tire pressure. Go by the car sticker, not the sidewall max.