Steel is the "Big Boy" material of choice. At 250 Lbs. all three of my bikes are steel (2 road, 1 mountain ) and their frames have never given the least bit of trouble. I had a steel Fuji which I rode for 11 years and the frame was as good on the day I donated it to the local public program, as the day I got it. For the "large framed" among us it can't be beat.