I have a set of straight bars in an adjustable ahead stem, that is kept in place with a curved plate and four allen bolts. Pretty standard. Had the bars for quite a while, the stem is about 4 months old. Very recently getting a creaking sound from the bars. Obviously happening as I put pressure on the bars alternately on each side. Tried feeling them as it creaks, and putting my ear against them whilst flexing the bars - not as I am riding! Seems to be from the bars on each side of the stem rather than the stem itself. It is bloody annoying on a long ride, but more concerned that it may be a sign of a problem with the bars and they may be about to break- which may be nonsense. Any ideas?