Originally Posted by
DiabloScott
Not sure why this is important since the cause here is certainly not fatigue.
But ALL fatigue starts with a crack. Steel frames with cracks will absolutely fatigue. Aluminum's lack of a fatigue limit means that the cracks can appear without previously being damaged - it doesn't mean it'll be a certain failure at an unsuspecting time.
In regards to this particular bicycle, there's no possible way for us to determine the direct cause of the OP's frame failure. All we can do at this point is speculate and discuss possibilities. The scientific data suggests that his frame failure was most likely, due to fatigue. How you can state unequivocally for certain, that it was not, is beyond my comprehension. Speculation always favors science, not anecdotal testimony.