My Dahon Mu P24 has the frame hinge creaking. It was really loud. The bike shop (that sold me the bike) tightened it. Not that much of an improvement. I put some lubricant on the hinge parts. I'm not sure if or how much it helped. Somehow it settled down a little bit. Now it creaks occasionally, usually when riding over a bump or pothole. The creaking sounds like a loud sharp crack. The hinge is as tight as it can safely be. I nick-named the bike Fireworks: it's beautiful, fun to use, but can get loud, just like fireworks.