The pictures here are of a 1968 Pugliaghi. Everything clamp on even the bottom bracket gear cable guides. Pictures from TheRacingBicycle.com
In the late 1950s through the early 1970s there was a slump in bicycle sales in Europe. In the 1960s the economy was booming and although in many places the bicycle had always been the mode of transport for the working classes; many were now buying cars for the first time. At the same time the fitness craze of the 1970s had not yet begun.
Racing bicycles and framebuilders were also hit by this slump and the price of a frame rose very little in that decade even though inflation did. Framebuilders had to look for ways to cut costs and one of them was to leave off all braze-ons.
Building a frame without braze-ons does save a considerable amount of time and therefore labor costs. The only braze-ons seen in this era was a chainstay stop and sometimes a little stop under the down tube to prevent the gear lever clamp from sliding down the tube.
Having done that framebuilders could not tell their customers they were doing this to cut costs, hence the story that braze-ons weaken the frame. I think Cinelli started it; framebuilding was never their main source of income (Handlebars and stems were.) so the price of a Cinelli frame was always high. Everyone’s thinking was if Cinelli can get away with it so can we, and most framebuilders followed suit.
Do braze-ons weaken the frame? Maybe very marginally but it is part of the framebuilding process. I have seen down tubes break right at the clamp on gear lever. Imagine a shock wave from hitting a bump in the road, or the twisting forces on a down tube.
Normally these stresses would be dispersed around the frame, but instead are stopped rather abruptly by a solid clamp around the tube. Clamps require more maintenance they collect moisture under them and if over tightened can dig into the tube and start a stress riser.
Prior to the “No Braze-ons” craze, all the various derailleur manufacturers provided clamp-on fittings because there was no standardization in gear lever design, for example, and clamp-on gear lever had already been standard practice for the most part.
By the 1970s, when braze-ons made a return, Campagnolo so dominated the market that most frames (Especially Italian.) came with a Campagnolo brazed on lever boss. Other manufacturers (Shimano for example.) were forced to design their gear levers to fit the Campagnolo lever boss.
I do feel if anyone is restoring a bike with a “No braze-ons frame” from this era should keep the cable clamps because they are authentic for that period.
Footnote: Re-posted from March 2006 with aditional content added.