please help diagnose...
without the chain attached, spinning crank makes a noise like there is sand in between something and it makes crunchy noises...very very subtle noise. i clean my chain ever 100 miles or so and wipe down bike after every ride. i just noticed this for the first time and it worries me. its an AL frame too so its hard to pinpoint the exact place. only thing i know is whenever i turn the crank i can hear it. with the chain on you could even tell.
is it possible small debris got in crank some how or frame has problem? i didnt see any fatigue in frame or cracks. i cleaned in between the gap where BB goes though frame (sorry dont know term) but still noise...