David Damerell wrote:
Benjamin Weiner wrote:

I "pinned" a 52 in an attempt to mimic the Shimano pins that
assist 42-52 upshifts. I tapped small holes in the chainring a bit
below the teeth, and inserted short M5 setscrews that poke inside
by 1-2mm, just enough so the chain doesn't hit them when it's on
the 42. If you do this I think the setscrews will push the chain
inside enough to land on the 42 when downshifting.

Ingenious - but do they help with upshifts? The derailleur cage doesn't
provide much upwards hoik, because it has to do most of its work for the
28-42 shifts.

Yes, slightly. This is on a 52-42-30 with plain rings and an old
RSX STI triple front lever with no trim adjustment. If it was a
friction front shifter, the plain rings would work ok. With the
STI, there is a limited range of adjustment where upshifts work,
the der can push the chain down to the granny, and chain rub is
tolerable. The pins improve front upshifting enough to widen
this workable range. Late model Shimano rings also have some
shorter teeth to help the downshifting - I've been tempted to file
down a couple of teeth to imitate that.

Front STI is hardly ideal, but front shifting can be clumsy
even with a friction shifter, especially under load. I know,
it's "better" not to shift the front under load but if you have
hills it's sometimes unavoidable. The mutated chainrings seem
to help with that.

WRT the derailleur cage and upshifts, sometimes rotating the
FD about the seattube slightly helps with that. Triple fronts
can be a battle between quicker shifting and tolerable
chain rub. I'd like to see the manufacturers improve front
shifting before adding more rear cogs, but given the degrees
of freedom in any crankset/FD combination, that may be quite
hard.