I just read the original article, and while it was interesting, I didn't see anything about how the author (Frank Berto) actually determined that the 15% drop was an ideal starting point. He mentioned in one paragraph how the experts agree that tire drop is important. Then in the next paragraph he stated that the magic number is 15%. He took some measurements to determine the necessary pressure to achieve the 15% for various tire sizes and bike & rider weight (credit to him for that, it does give us something). I understand the author is giving the value as a place to start, but where is the evidence/experiments/calculations, anything to convince a curious reader/rider that there is validity in 15% tire drop. No insult intended to Berto, the OP or anyone else, 15% may be the correct value but its hard to tell based on the article.