Regarding Campagnolo's 12S components, back when only wired EPS was available,
the tooth count configurations were:
Crankset side:
53–39T
52–36T
50–34T
Sprocket side:
11–29T
11–32T
11–34T
All three of these sprockets had the same top eight cogs:
11–12–13–14–15–16–17–19T
This was a pretty clever setup with "16T always included"
and "at the level of competitive riders,
all tooth count combinations feel the same on flat roads."
Later, when wireless WRL came out,
the compact drive philosophy was
imposed in a different way:
Crankset side:
48–32T
45–29T
Sprocket side with N3W freebody:
10–25T
10–27T
10–29T
11–32T (S WRL only)
were added.
"If outer × top is 48×10T,
the gear ratio is 4.8x,
4.8x would be equivalent to a 53T front cog
with a theoretical sprocket tooth count of 11.0416...,
so 53×11T equivalent—that should work," is the logic,
but riders at the level supplied with components
tend to dislike the compact drive philosophy.
When SRAM once tried to impose a 50–37T configuration
(and 48–35T and 46–33T by reducing 2T each)
on pro riders,
they said "make us run 53–39T"
and had non-retail 53–39T
prepared specially for them.
These days it's gotten even more extreme,
with radical combinations like 56×10T appearing,
so regulation might be coming.
As for me, I think it's nice that Campagnolo 12S
lets you choose a combination like
52–36T and 10–25T.
Though I haven't actually bought one.
The recently released Campagnolo 13S WRL
has a maximum capacity of 41T,
with crankset side:
45–29T (16)
48–32T (16)
50–34T (16)
52–36T (16)
53–39T (14)
54–39T (15)
55–39T (16)
and sprocket side:
10–29T (19)
10–33T (23)
11–32T (21)
11–36T (25)
The numbers in parentheses are gear capacities,
and no matter how you combine front and rear gears,
the total stays within 41,
so it's a "anything goes within officially available combinations" spec
that doesn't require users to do calculations or verification.
Crank lengths come in four sizes: 165, 170, 172.5, and 175mm,
but with seven chainring variations,
I guess they figured dead stock would pile up,
so the 13S WRL has cranksets and chainrings sold separately.
Now to deliver on the title.
The image above is the front derailleur
of the 12S Super Record S WRL,
and there are two mounting bolt holes
positioned to accommodate the range of outer chainring tooth counts.
The helicoil insert on the upper hole
hasn't had its end breakaway section removed,
but since it's not a through-hole, that's fine.
↑The helicoil is installed by gripping the part that crosses the circle at the end
with a specialized tool and turning it in,
then tapping it off with a punch at the end.
The helicoil has a certain number of coils,
though it seems like adding a couple more coils wouldn't hurt,
but that's fine too.
↑This is the 10S Chorus CT front derailleur
(with a hole drilled messily into it)—it's mine.
CT stands for front derailleur for compact gears,
and back then the smallest inner gear tooth count was
39T on a 135mm PCD,
but Campagnolo also made
compact gears with 110mm PCD (113mm on the crank back)
with a minimum of 34T, or 36T on other specs.
Since the front derailleur capacity itself was adequate,
it was technically possible to use
a conventional front derailleur with compact cranksets,
but as the preferable option,
they released the CT front derailleur
with the inner cage set deeper downward.
↑Drilling a through-hole here
doesn't interfere with the adjustment bolts.
Anyway, not important.
I removed the mounting bolt.
There's just one threaded hole.
The regular pattern of small indentations
is from when I pressed it onto
a Colnago steel frame's direct-mount bracket with its anti-slip knurling.
Back then, Colnago and other Italian bikes
typically had front derailleur mounts designed
to reach up to 55T but couldn't drop down
even to 50T, let alone 48T.
Back when I was racing at Norikura
on a Colnago Master X-Light
that would weigh "6.4kg with a steel fork,
under 5kg with a carbon fork,"
it had a 48–34T crankset
and by the way a 12–27T sprocket
so the front derailleur couldn't be positioned
low enough for proper adjustment.
↑So I made something like this.
By swapping parts on the front derailleur,
you can convert it to two holes.
Seeing the Super Record S WRL front derailleur
brought this to mind,
so I pulled out the Chorus CT.
the tooth count configurations were:
Crankset side:
53–39T
52–36T
50–34T
Sprocket side:
11–29T
11–32T
11–34T
All three of these sprockets had the same top eight cogs:
11–12–13–14–15–16–17–19T
This was a pretty clever setup with "16T always included"
and "at the level of competitive riders,
all tooth count combinations feel the same on flat roads."
Later, when wireless WRL came out,
the compact drive philosophy was
imposed in a different way:
Crankset side:
48–32T
45–29T
Sprocket side with N3W freebody:
10–25T
10–27T
10–29T
11–32T (S WRL only)
were added.
"If outer × top is 48×10T,
the gear ratio is 4.8x,
4.8x would be equivalent to a 53T front cog
with a theoretical sprocket tooth count of 11.0416...,
so 53×11T equivalent—that should work," is the logic,
but riders at the level supplied with components
tend to dislike the compact drive philosophy.
When SRAM once tried to impose a 50–37T configuration
(and 48–35T and 46–33T by reducing 2T each)
on pro riders,
they said "make us run 53–39T"
and had non-retail 53–39T
prepared specially for them.
These days it's gotten even more extreme,
with radical combinations like 56×10T appearing,
so regulation might be coming.
As for me, I think it's nice that Campagnolo 12S
lets you choose a combination like
52–36T and 10–25T.
Though I haven't actually bought one.
The recently released Campagnolo 13S WRL
has a maximum capacity of 41T,
with crankset side:
45–29T (16)
48–32T (16)
50–34T (16)
52–36T (16)
53–39T (14)
54–39T (15)
55–39T (16)
and sprocket side:
10–29T (19)
10–33T (23)
11–32T (21)
11–36T (25)
The numbers in parentheses are gear capacities,
and no matter how you combine front and rear gears,
the total stays within 41,
so it's a "anything goes within officially available combinations" spec
that doesn't require users to do calculations or verification.
Crank lengths come in four sizes: 165, 170, 172.5, and 175mm,
but with seven chainring variations,
I guess they figured dead stock would pile up,
so the 13S WRL has cranksets and chainrings sold separately.
Now to deliver on the title.
The image above is the front derailleur
of the 12S Super Record S WRL,
and there are two mounting bolt holes
positioned to accommodate the range of outer chainring tooth counts.
The helicoil insert on the upper hole
hasn't had its end breakaway section removed,
but since it's not a through-hole, that's fine.
↑The helicoil is installed by gripping the part that crosses the circle at the end
with a specialized tool and turning it in,
then tapping it off with a punch at the end.
The helicoil has a certain number of coils,
though it seems like adding a couple more coils wouldn't hurt,
but that's fine too.
↑This is the 10S Chorus CT front derailleur
(with a hole drilled messily into it)—it's mine.
CT stands for front derailleur for compact gears,
and back then the smallest inner gear tooth count was
39T on a 135mm PCD,
but Campagnolo also made
compact gears with 110mm PCD (113mm on the crank back)
with a minimum of 34T, or 36T on other specs.
Since the front derailleur capacity itself was adequate,
it was technically possible to use
a conventional front derailleur with compact cranksets,
but as the preferable option,
they released the CT front derailleur
with the inner cage set deeper downward.
↑Drilling a through-hole here
doesn't interfere with the adjustment bolts.
Anyway, not important.
I removed the mounting bolt.
There's just one threaded hole.
The regular pattern of small indentations
is from when I pressed it onto
a Colnago steel frame's direct-mount bracket with its anti-slip knurling.
Back then, Colnago and other Italian bikes
typically had front derailleur mounts designed
to reach up to 55T but couldn't drop down
even to 50T, let alone 48T.
Back when I was racing at Norikura
on a Colnago Master X-Light
that would weigh "6.4kg with a steel fork,
under 5kg with a carbon fork,"
it had a 48–34T crankset
so the front derailleur couldn't be positioned
low enough for proper adjustment.
↑So I made something like this.
By swapping parts on the front derailleur,
you can convert it to two holes.
Seeing the Super Record S WRL front derailleur
brought this to mind,
so I pulled out the Chorus CT.