Keep in mind that door sticker pressures are designed to be SAFE; they are not designed for the best handling.
Ma and Pa Kettle will be fine at door sticker pressures. The rest of us may want to maximize our traction and performance and potentially use pressures to balance out the handling a bit.
Some people feel door sticker pressures don't apply if they have changed from OEM. This is not true. Door sticker pressures will almost always be safe, no matter what you put on there. Unless it is some made-in-China counterfeit import (and there are a lot of them out there - all with very North American-sounding 'adventurous' names) they just don't make tires in our correct size that would be unsafe at those pressures.
Ah, but what if we want not just SAFE, but the BEST pressure for our individual purposes. A rule of thumb is that a P-size tire develops its best traction at around 80% of maximum sidewall pressures. Your maximum sidewall pressures are 44 PSI, so therefore, your best traction is at 35 to 36 PSI. Now, you need to determine your own individual driving style, the load you traditionally carry and how far you want to push handling.
Me, I would say 30 is too low for the front. If I corner hard, the tires would tend to 'tuck under.' I want maximum traction in the front to minimize the designed-in understeer of these vehicles, and I want to prevent tuck-in in an emergency, so I am running my fronts at the high end of the maximum traction plateau.
Now the rears. I don't carry big loads, plus I can always go higher (up to 44 if necessary) when carrying a load. I want a bit of a softer ride, and the rear tire pressures contribute more to that ride than the front in most cases. Therefore, I am going toward the softer end of the traction plateau. So what would I run for my driving style with those tires? 35 front; 33 rear when lightly loaded, and 35 front; 40 rear when carrying a load. (I don't corner at 9/10s with a heavy load in the back because that would be dumb.)
Now understand that is me. Everyone is different. I am very sensitive about things like dynamic balance and traction circles, and I even went to a slightly stiffer rear sway bar just to make the handling of my truck more neutral.
So i would suggest you try coming down in 2 PSI increments for several weeks and see which one you like the best. I agree that 38 is pretty high. I am willing to bet you are going to be much happier at 33 to 35 front and rear.
(By the way, door sticker pressures have changed over the years, not because our platform has changed but because the philosophy has changed. Companies like GM realize that the vast majority of drivers are stupid, and if they say 30 rear, but pump them up to 38 when carrying a load, Ma and Pa will leave them at 30 forever, even when taking 1000 pounds of gear and four friends home from the cottage at 140 on the interstate. By specifying 35, they are better covering themselves for the majority of the crappy drivers who wouldn't know the difference between understeer and oversteer if it reached out from a corner and hit them over the head with the armco.)
