Wold Ranger wrote:
Most of them will have broken at the top tube piercing, 6061 has a very low fatigue life and as the triple triangle design effectively left the top tube/seat tube interface not particularly well braced, especially where you had a lot of seat tube out! (fine for the original crmo steel frames!) They cracked just in front of the piercing. GT alloy was never very good and breakage has always been an issue. I saw lots of the Carbon/Alloy Lobo frames break but across the alu' lugs not the square carbon tubes.
Most of them? I think that you're making a sweeping generalisation based on a couple of broken frames that you saw. The Zaskar has a reputation for being one of the most bombproof frames you can get (could get) I'm not sure that it would have gained that rep if 'most' of them had fallen to bits by now.
Also, in a previous post, you said that the 6061 models were made with Easton tubing, which has a pretty good reputation.