This is a short video about how to fix the squeal on MAFAC center-pull brakes. These brakes are known for and susceptible to squealing, and are original to a Peugeot Mixte, a vintage French bicycle.
I tried all the usual methods for reducing squeal such as replacing the brake pads, scuffing the brake pads with sand paper and adjusting the toe-in on the brake shoes. None of these worked. That is because the squealing comes from the vibration of the brake arms caused when the pads rub against the bicycle rims.
To get rid of the vibration, move the brake pads as close as possible to the brake arms.
My video left out a few steps. Hopefully you get the idea without me showing every step. If you still need more help, have a look at the more detailed instructions below. This is applicable to both front and rear center-pull brakes.
1. Loosen the brake pads, and move them as close the brake arms as possible. Finger tighten them to a proper position so when you pull on the brake lever, the pads are aligned to the rims.
2. Now that the brake pads are backed all the way out, take your vise grips or have a helper squeeze the brakes together for you so that the brake pads bottom out to the rims. Note: if you like, place a piece of cardboard, or other material to use as a shim between the brake pads and the rim. This will help you maintain some gap between the brake pads and the rims so that they will spin freely.
3. Tighten up the slack on the brake's bridge cable, as shown in the video.
4. Remove the vise grips and tighten your brake pads.
5. Move silently like a Ninja.