Originally Posted by
verktyg
In the early 80's Peugeot, Motobecane and Gitane started making frames for their lower priced bikes that way. The marketoid BS claim was that it was better than a lugged frame. The real reason was to cut costs to compete against the deluge of cheap Asian hitting the European market,,,.I've never seen any frame failures on those internally brazed French made bikes....
Internal brazing had one other significant advantage over lugs, in that it allowed visual inspection of the quality of the joint. With lugs, the joint is hidden underneath the lug. It's impossible to determine the penetration without very sophisticated, expensive and time consuming equipment. With the lugless brazing systems, the larger fillet is on the inside of the tube but the amount and characteristics of the reflow on the outside of the tube allowed inspectors to gauge the quality of the internal fillet.
This allowed Peugeot to catch the vast majority of defective frames before they left the factory and before Peugeot invested the time and money in painting and assembly of the bicycle. It saved them a lot of money not just manufacturing but in warranty claims. This ability to visually inspect the quality of the joint is a big factor in why you've never seen any failures.