I recently bought a Trek Navigator 3.0 with rapid fire shifters. It seems that when I shift in to certain gear ranges it sounds like it's between gears. I took it back to the dealer and he said it was because the chain is up against the edge of the sprocket in certain gears and that it's not meant to use all the gears, but mostly the ones in between. Has anyone else had this problem or is it normal? Any advice at all would be appreciated.