...have insufficient rear brake bridge brass (EDIT: silver) penetration?
This just popped up in the Framebuilder's forum:
Some of you might remember that my Trek 728/720 also popped a few years ago from relatively little stress. I had a $hitty tig-weld put in the gap:I was changing the rear wheel on my older Trek when "pop" the cross tube that holds the rear brake pulled free from one of the seat stays. Looking at the joint is it rusted except for one tiny 1/8" spot so this has been just waiting to let go for a while.
Several years ago the rear end was damaged and the seat stay had to be bent back into shape. I assume this put pressure on this joint or cracked the weld then and it has just now given up.
From what I can see, hardly any brass was present in either of these joints. With all due respect to JohnDThompson - what the hell was Trek's framebuilders doing?