My bike has about 10,000mi. on it and has been lovingly cared for. It has always been a real quiet runner so any noise is noticeable. I'm not smart enough to figure out where the noise is coming from, but it does cause me concern because it is so unusual for my bike. Initially, I thought it was from the drive train. When they put it on the stand and ran it through the gears, it was perfect. When I was riding last night, my bike was making a clicking sound when under load, like climbing a hill in a harder gear. It was fine when I was spinning on a flat surface. How does a mechanic duplicate a bike under load when he has it on a stand? Or is it even necessary? Are they able to detect a problem without duplicating the exact conditions at which the problem occurs? I guess my concern is that I'm developing a problem with my bottom bracket. How many miles can you get out of a bottom bracket?