I have a 2002 Kestrel road bike that makes a clicking noise while pendaling down. The sound comes from bottom bracket/front derailleur area. And it only happens when the right crank is pointing straight up to when it's pointing down (about 180 degrees). Perhaps because that's when most of the force is put on to the crank. All crank bolts and crankarm attachment to the bottom bracket is secure. I don't hear the sound when I'm riding gently, only when I'm pushing the right crank arm really hard (i.e. when accelerating after stop or to speed up while moving). When I do the same to the left crank arm it doesn't make this noise.
I took it to my LBS and first they made sure all the nuts and bolts were tight. Then the sound was still there. The mechanic concluded that since it's an old Kestrel carbon frame bike the frame is flexing and causing the chain to rub the front derailleur when I put a lot of force on it. I'm not 100% convinced that this is the case. I guess one way to find out if this is the case is for me to take off the front derailleur entirely and see if the sound is still there? Has anyone else experienced a similar condition? Please help.