When Randy and I started discussing what he wanted in a new frameset, he was definite about wanting to modify a rare set of DiaCompe 700 centerpull brakes to mount via braze-on bosses. The photo below shows this brake model as it was originally produced, with the beautifully designed caliper arms mounted using a universal-fit yoke and center bolt.
In contrast to Mafac centerpulls which are readily convertable to braze-on bosses, the center-mount DiaCompe 700 uses a spring shape which doesn't allow the original spring to anchor to the boss as it should. In addition, the dimensions of the DiaCompe's pivot are sufficiently different from current brake standards that this brake doesn't mate with stock bosses. The solution was to fabricate a set of hand-wound stainless steel springs. After several prototypes, I arrived at the spring profile shown in the photo below.
This photo also shows the custom braze-on bosses that I made for this project. The dimensions on these bosses are optimized to mate with the DiaCompe 700 brakes' original pivot bushings. And, since bosses and springs were designed in concert, the single spring anchor hole is all that's needed.The photo below shows the DiaCompe 700 brake arms mounted to the braze-on bosses. Those are 50mm fenders mounted with 13mm of clearance over 35mm Pasela tires. These brakes are both beautiful and well designed, and I'm happy to give them a second life on this new All-Road frameset that I know Randy is going to ride hard.
Update ... After updating these brakes with modern Kool Stop pads, pulley-style hangers and shorter straddle cables, Randy reports "I've never ridden with brakes that stop so well and modulate so nicely. All that work was well worth it." 