You know this already. You have been there, this will not come as a surprise to you – sometimes you simply, really must leave well enough alone. And I didn’t.
A couple of years ago, I looked at my newly restored Bertin C 37 and thought that high flange Maillard 700 hubs would be a perfect match for the look I wanted. There already was a set of completely competent low flange Maillard Sport hubs with Mavic E2 rims but it had to be 700s. Two complete sets of hubs later, I pieced together one usable set of functioning hubs and started looking for rims. You can find the whole drawn out story here, if you must.
Eventually, the wheels were built and then the squealing began. Now you understand the opening paragraph’s warning. My Bertin 
has brazed-on pivots for its first generation MAFAC 2000 centrepull brakes. Theses are rigid, carefully 
aligned and, with my old wheels, there was not a hint of the dread MAFAC squeal even given the centuries old, original equipment MAFAC rubber brake pads.
This all ended with the change of wheels but the squealing was eventually brought under control with careful sanding and cleaning of the PBP rims. The only thing was, I now noticed that the braking was really not up to the standard I would have expected.
Typically, you grabbed a handful of lever. The lined housings and coated wires transmitted the force smoothly to the calipers and then not much happened. More force, more of “not much” until, eventually the bike would stop – without squealing, I might add. Obviously, something further needed to be done.
What I wanted was a replacement cartridge that would look original and fit the OEM MAFAC brake shoes. Kool Stop was kind enough to manufacture such a product in both an orange, wet weather compound and a stock looking black one, both of which are correct even to the number of bumps on the pad. At $25 for four pads, the price was reasonable and, after a recommendation from Tim M. whose bike has been featured here, I ordered a set from Harris Cyclery in the US. Delivery was prompt but the customs duty hurt.
Once unpacked, the pads looked like the illustration below on this page. There were the 4 pads, illustrated installation 
instructions and a free decal with which you can deface your bicycle or your toolbox, as you prefer.
The pads were cleanly molded and virtually free of moulding flash and were ready to install fresh out of the package.
One interesting thing about the Kool Stops was the fact that pressing a nail into the surface left a slowly rebounding dent that eventually disappeared. The same treatment of the original MAFAC pad left no impression whatsoever!
The Kool Stops had their braking surfaces scuffed up with 320 grit sandpaper to make sure the surface was completely flat and that any mould release material was removed before calling on the pads to stop a fast-moving bicycle. The original photo shows the slightly 
glossy finish of the original mouldings but the photo of the single pad shows the braking surface during sanding. Notice the crumbs and bits of rubber on the sandpaper indicating the softness of the compound. The OEM pad left nothing but fine black powder after similar treatment.
Once the sanding was finished, installation was relatively straight forward. Release the return springs on the brake caliper being worked on. Loosen the mounting bolts for the brake shoe and slide the post out of the brake mounting.
Look carefully at the front of the shoe. If you have a genuine MAFAC pad holder, there will be a space or slot between the end of the rubber pad and the aluminium of the pad holder. The original designers put that there so that you can slide a straight bladed screwdriver in and then lever the rubber shoe partially out the open back end of the pad holder. Hold the mounting post with your fingers and grasp the partially ejected rubber shoe with pliers and withdraw it from the holder.
If you immediately attempt to fit new pads in the old holders you are going to have a problem. The MAFAC pad is about 8.5 mm at the shoulders where they slide into the alloy pad holder. The Kool Stops are 9mm. No problem – get a Q Tip (cotton swab) and smear a little dilute, liquid dish soap on the rubber shoulders of the pad and on the edges of the pad holder. Slide the pad firmly into the pad holder. Then, as they love to tell you in technical manuals, reverse disassembly and then repeat.
The road test was a revelation. On a clear, dry 20 degree C day, braking was super smooth, modulation was precise and linear and there was no squeal whatsoever. Repeated braking over 20 minutes of acceleration and deceleration produced no fade and no change in braking characteristics.
Conclusion: Kool Stop makes an excellent product which performs well and does so looking as if it got there with the original brakeset. If you have any variety of MAFAC which takes the 4 dot pad, this may be exactly what you are looking for. If you tour in wet weather, possibly consider the orange compound Kool Stops instead and forego that black pad originality for even better performance.
Bertin Classic Cycles 