Originally Posted by
unterhausen
I've seen aluminum frames that cracked at the seat cluster because they were too light. I would say that isn't a good design, even though not every one cracked. You see some frames that have common failure points. Often at the seat cluster because it isn't obvious that is a highly stressed joint
That's why separate seat collars started to show up on bikes. There have been plenty of similar idiot-proofing modifications made to steel frames. We take them for granted simply because they were instituted at a much earlier stage in the development of the steel frame.