Originally Posted by ghettocruiser
Hmm. I actually have a pile of cracked steel frames in my basement and ride all aluminum these days.
Yep. I've had at least a dozen steel frames of various quality fail in fatigue, as well as one Ti frame. Haven't had an aluminum frame fail so far. I remember when aluminum frames first started getting popular, everyone talked about how they would all crack to pieces. Generally speaking, it just hasn't turned out that way-aluminium frames are very reliable, all things considered.
The design and construction quality of the frame is far more important than the material it is made out of. Just because steel has an infinate fatigue limit below some stress threshold doesn't mean that every steel structure is designed to take advantage of that property. Throw welds and stress risers into the mix, and things get way more complicated.