Data points: * Cannondale Optimo: cracked downtube in under 2 years/12,000 km * Trek 2.3: still okay after 10 years/70,000 km. * Trek 1500: cracked drive side chainstay (age/distance not stated) -------------------------------------- Today my Optimo 63cm ( a Cannondale , pioneers of Aluminium bicycle frame... ) develop a crack around the diameter of the downtube, only 3 cm remaining holding the tube in one piece. Tired of the mis-shifting of the rear derailleur in danseuse mode, I stopped to check. And that’s when I see this huge crack... I just had to look at the right place. It’s a little scary , cause I just went down several hills at 65 km/h (40 mph). Really didn’t think this would happen on a less than 2-year-old frame , with less than 12,000km. At 6'4'' (193cm) , I'm only 180 lbs (82 kg). I also have an aluminum Trek 2.3 that is 10 years old and with at least 70,000km that has no frame problems. Its end is probably near but I was much more satisfied for its durability . I must say that I had got it for replacing a series 1500 model ( entry level trek ) which had cracked its drive side chainstay. Yes the Trek 2.3 gives a rough ride and the Optimo is really comfortable in comparison. But I was close to finding hospital beds very uncomfortable for long term . I guess not all aluminum frames are born equal. I just hope that Cannondale have a warranty equal to Trek, I am waiting for the result of their investigation on my frame .