I recently undertook some open heart surgery on the Madone, in an effort to track down and eradicate an elusive creak.
In the time before undertaking that work, I realized that bike creaks are very Schrödinger. Until you diagnose exactly where they’re coming from, they both are and are not every part on the bike–there’s a great deal of creak entanglement. The bottom bracket is both fine and failing. The pedals are both loose and tight. The seatpost is both shifting and stable.
The only way to truly determine the origin of the creak is fixing the creak. Tightening the pedals doesn’t work by itself–you have to try everything until the creak is resolved. Because until you fix the creak, it is still there and you don’t know what it is. Maybe you tightened the pedals but didn’t put grease on them, and it’s still the pedals creaking. Or maybe it is the bottom bracket.
That Schrödinger…he knew a lot of things. He is not often given credit for his bike-related work, however.