I've got a soft metallic rattle in my BB. I've isolated it to the BB/crankset (put it on stand, rap frame with my hand while listening with auto mechanic stethoscope). Noise is still there after I remove the pedals, so that's not it. It's an FSA SLK light BB30 crank on an 06 carbon Synapse (DA groupo). The crank feels totally solid on the road & I cannot hear it while riding. Any ideas to eliminate this annoyance???