Originally Posted by
thompsonpost
Usually metal fatigue. Not hard core stress, at least in my usage. Normally just behind the seat tube at the top adjacent to the top tube. YMMV, and there are sure to be many answers after mine. I've had two Diamondbacks fatigue in the same spot.
Interesting.
My 1994 Cannondale owners manual came with a warning to regularly inspect the area under the point where the downtube meets the head tube.
It's now 16 years old, and I am still riding it.
(Of course the only original parts are the frame, fork, and handlebar.)