I haven't chimed in on this but what the hey, here I go.
Flex it the enemy of braking. Older brakes compensated for this in a
couple of ways but the most important was pad softness. Older pads were
softer-cf: MAFAC-to follow the rim as the caliper flexed. Weinmann and
Universal were the same. Remember how fast those pads wore out?
In comes Campy with about the stiffest calipers made to the time. But
they paired them with the hardest pads we'd ever seen. Remember how
every ride was followed by a session picking aluminum flakes out of the
pads? This was the "speed modulation" theory. Of course those non
pelotonists among us needed to actually stop and hated picking our rims
out of the pads so guess what? We switched to Scott Mathauser pads as
soon as they came out.
Viola! Braking problems solved.
The problem is that modern pads are harder than vintage pads. Even if
they are vintage pads they've hardened over the past 20 or 30 years on
the bike shop shelf so now we have the worst of all possible worlds:
flexy calipers with hard pads and poor stopping.
I hope this brings some new thought to the discussion.
Phil Brown
Berkeley, Calif.