Need advice/input after broken frame
A little context: I am 6'5 and around 215 lbs, give or take a few depending on the time of year, and just this past week had the frame of my main bicycle fail. It is an aluminum frame endurance bike from a name brand and developed a crack in the seat tube a few millimeters above the top tube weld (between the seat post clamp and the top tube weld). I have taken it to my LBS where I purchased the bike a little over a year ago and warranty procedures are under way.
This is the second bicycle frame I have had fail. Previously I had the seat tube on my old hybrid shear a few centimeters up from the bottom bracket. I was around 250 lbs when I purchased that bike and started riding. I put a good 5 or 6 years on it doing city commuting and weekend rides. I was a little surprised it broke the way that it did, but I put a lot of wear on it. Not so much with my newer road bike that just broke this past week. Summary over.
The guys at my LBS have been extremely helpful (even since before I purchased this bike from them) and I dont think they were giving me a line of marketing BS (they were not trying to sell me anything), but I wanted to get a second opinion from the community. I asked them what I could do to prevent these types of things in the future. I know I am a big guy, but I'm not huge. This failure rate seems a little too frequent (in my relatively uninformed opinion). They said there wasnt really an answer and that frames fail. They did suggest that the allowed flex in carbon fiber frames will cut down on stress fractures like what just happened to my road bike. They were also saying that CF bikes can be built more to purpose and adjusted based on the size of the bike and rider so that stressed areas get built up more.
Im just not sure what the answer is to reduce frame failure rates. Steel? Titanium? Custom built so that I actually get a properly sized bike for me?
Im curious if other people experienced in the industry have any thoughts on failure rates, merits of frame material X versus Y, or general advice for frame styles/types for those of us who barely fit 61cm mass produced bikes?
Thanks!