Here’s a really good article that explains the trend towards wider rims and lower pressure.
“One of the biggest shifts in road cycling in recent years has been the move to wider tires. By spending less than $100/£70/€90 on a pair of 25mm wide or wider tires, many cyclists have been led to believe their comfort, speed and handling will immediately improve over what they experience on the 23mm wide tires that most of us have used for years.”
And later on in the article…
“No matter what width tire you are running, the key here is to find the right pressure to inflate your tire. For that I suggest you start with a table provided by your tire company and a little trial and error of your own. Tire companies vary quite a bit in what they recommend or even how specific they are willing to get…” Read more