The electronic rear derailleur RD-6770 from my Shimano 10-speed Altus groupset
that I had on my cyclocross bike
has suddenly passed away.
This is what's scary about electronic groupsets.
When I connected it to the diagnostic kit, only the rear derailleur showed no response,
and when I plugged other electronic rear derailleurs
into this bike's rear derailleur cable,
they worked normally,
so it's confirmed that only the rear derailleur is dead.
So I procured an RD-R8050,
which is still readily available today.
The used market price for an RD-6770 was
about the same as what I paid for the RD-R8050.
The electronic cable is common with the EW-SD50
(and these two rear derailleurs are actually
the first and last models compatible with EW-SD50),
but the supported sprocket count is
11-speed rather than 10-speed,
so it won't work with my current rear wheel.
So I'm also preparing a "10-speed sprocket with 11-speed spacing
(made by removing one cog from an 11-speed)."
Because of the tooth count on the biggest cog,
I had installed a Wolf Tooth Road Link (→here),
but since I'm switching to a GS rear derailleur
and the next sprocket's largest cog is 30T, I'm removing this.
I removed the rear wheel.
The original sprocket tooth counts were
10-speed 14–25T and 11–40T (→here).
I removed the sprockets.
On one freehub body,
I'm installing a CS-6800 11–23T
with the 16T removed.
On the other freehub body,
I'm installing a CS-R7000 11–30T
with the 11T removed, but...
The 13T, which would be next to the new top cog,
is a "regular 13T," so this also needs to be replaced.
↑These are the original 11T and 12T, but
The top two cogs have a portion of the top cog
that fits into the notch of the next cog
in this structure.
So I procured 12T and 13T cogs for a 12T-start setup.
I ordered them as CS-R7000 parts,
but they have the same part number as
the spare parts from the earlier CS-5800,
which is also a 10-speed 105.
In the image above, from right: original 11T, 12T, 13T
In the image below, from right: next 12T, 13T
The reason I chose 11–30T for the larger sprocket
(before removing teeth) was that
11–32T would have odd-numbered cogs in the middle like 14T, 16T, 18T, 20T, 22T,
which I'm not used to pedaling on (especially on the low end),
and 11–34T shares grades with Deore for MTB,
making the spec "11-speed sprocket mountable on a 10-speed freehub"
unnecessarily complicated.
When I measure the thickness of the spacer between gears on 11-speed sprockets with calipers,
it's roughly 2.2mm (nominally 2.18mm),
and the thickness of one tooth on a sprocket is
roughly 1.6mm, totaling 3.8mm.
The difference in spline length between
a 10-speed freehub and an 11-speed freehub is 1.85mm,
so the current 10-speed freehub is
in the same state as an 11-speed freehub with a 10-speed conversion spacer (1.85mm) installed,
leaving 3.8–1.85 = 1.95mm,
and if I add another 10-speed spacer there,
the remaining gap becomes 0.1mm,
so I decided to
"install the modified 11-speed sprocket (with one tooth and one spacer removed)
on an original 10-speed freehub that already has a 10-speed spacer installed."
The shift adjustment becomes "specific to this wheel,"
but there's no problem.
↑11–23T side
↑12–30T side
↑11–23T
↑12–30T
Compared to the previous 14–25T and 11–40T combination,
this is a less interesting pairing,
but if I were to mount a 12-speed sprocket on an 11-speed freehub,
the most cross-ratio and wide-ratio combinations available in that grade would be
11–30T and 11–34T for Dura-Ace and Altus,
and 11–34T and 11–36T for 105,
leaving almost no point in having dual freehubs.
But even before that, it's impossible to realize
both disc brakes and dual freehubs
at the same time.
The RD-R8050-GS supports
a minimum low gear of 28T,
and a maximum of 34T,
but depending on the end adjustment bolt setting,
it can cause chain drop even at 30T,
so I adjusted it to the tightest point where this doesn't occur.
This is a front single-ring bike,
but for a front double setup, this adjustment would
put the third cog from the bottom on the inner ring
(on electronic groupsets, not entering the top two cogs in inner mode) into
a potential slack-chain condition (→here).
With the same rear derailleur settings,
I switched the rear wheel to the 11–23T side.
Since this rear derailleur doesn't support this tooth count anyway,
there's a gap between the sprocket and the upper pulley,
but shifting itself works fine.
This bike currently has no shifting function
on the brake lever area.
The image above shows the only shifter,
with button A on the right side (outside) for shifting toward the top,
and button B on the left side (inside) for shifting toward the low end.
Furthermore, there's no component equivalent to the upper junction,
so shift adjustment can only be done by connecting the rear derailleur alone to the diagnostic kit
and adjusting on the PC screen.
At Shimano, the top gear side is the higher number,
so as shown in the image above, the top cog is 11,
and 1 is the low gear.
But since I've removed one tooth from the sprocket,
the low gear is now 2.
If I were removing 4 speeds from 11 (→here), that would be one thing,
but for just removing 1 speed, adjusting only the set screw on the adjuster was enough.
Even if I shift to 1, the chain won't drop inward,
but the rear derailleur works hard to get the chain into the 11-speed low gear,
the motor squeaks "meep meep meep," and it puts considerable strain on things,
so I must not press button B when it's on 2.
that I had on my cyclocross bike
has suddenly passed away.
This is what's scary about electronic groupsets.
When I connected it to the diagnostic kit, only the rear derailleur showed no response,
and when I plugged other electronic rear derailleurs
into this bike's rear derailleur cable,
they worked normally,
so it's confirmed that only the rear derailleur is dead.
So I procured an RD-R8050,
which is still readily available today.
about the same as what I paid for the RD-R8050.
The electronic cable is common with the EW-SD50
(and these two rear derailleurs are actually
the first and last models compatible with EW-SD50),
but the supported sprocket count is
11-speed rather than 10-speed,
so it won't work with my current rear wheel.
So I'm also preparing a "10-speed sprocket with 11-speed spacing
(made by removing one cog from an 11-speed)."
Because of the tooth count on the biggest cog,
I had installed a Wolf Tooth Road Link (→here),
but since I'm switching to a GS rear derailleur
and the next sprocket's largest cog is 30T, I'm removing this.
I removed the rear wheel.
The original sprocket tooth counts were
10-speed 14–25T and 11–40T (→here).
I removed the sprockets.
On one freehub body,
I'm installing a CS-6800 11–23T
with the 16T removed.
On the other freehub body,
I'm installing a CS-R7000 11–30T
with the 11T removed, but...
The 13T, which would be next to the new top cog,
is a "regular 13T," so this also needs to be replaced.
↑These are the original 11T and 12T, but
The top two cogs have a portion of the top cog
that fits into the notch of the next cog
in this structure.
So I procured 12T and 13T cogs for a 12T-start setup.
I ordered them as CS-R7000 parts,
but they have the same part number as
the spare parts from the earlier CS-5800,
which is also a 10-speed 105.
In the image above, from right: original 11T, 12T, 13T
In the image below, from right: next 12T, 13T
The reason I chose 11–30T for the larger sprocket
(before removing teeth) was that
11–32T would have odd-numbered cogs in the middle like 14T, 16T, 18T, 20T, 22T,
which I'm not used to pedaling on (especially on the low end),
and 11–34T shares grades with Deore for MTB,
making the spec "11-speed sprocket mountable on a 10-speed freehub"
unnecessarily complicated.
When I measure the thickness of the spacer between gears on 11-speed sprockets with calipers,
it's roughly 2.2mm (nominally 2.18mm),
and the thickness of one tooth on a sprocket is
roughly 1.6mm, totaling 3.8mm.
The difference in spline length between
a 10-speed freehub and an 11-speed freehub is 1.85mm,
so the current 10-speed freehub is
in the same state as an 11-speed freehub with a 10-speed conversion spacer (1.85mm) installed,
leaving 3.8–1.85 = 1.95mm,
and if I add another 10-speed spacer there,
the remaining gap becomes 0.1mm,
so I decided to
"install the modified 11-speed sprocket (with one tooth and one spacer removed)
on an original 10-speed freehub that already has a 10-speed spacer installed."
The shift adjustment becomes "specific to this wheel,"
but there's no problem.
↑11–23T side
↑12–30T side
↑11–23T
↑12–30T
Compared to the previous 14–25T and 11–40T combination,
this is a less interesting pairing,
but if I were to mount a 12-speed sprocket on an 11-speed freehub,
the most cross-ratio and wide-ratio combinations available in that grade would be
11–30T and 11–34T for Dura-Ace and Altus,
and 11–34T and 11–36T for 105,
leaving almost no point in having dual freehubs.
But even before that, it's impossible to realize
both disc brakes and dual freehubs
at the same time.
The RD-R8050-GS supports
a minimum low gear of 28T,
and a maximum of 34T,
but depending on the end adjustment bolt setting,
it can cause chain drop even at 30T,
so I adjusted it to the tightest point where this doesn't occur.
This is a front single-ring bike,
but for a front double setup, this adjustment would
put the third cog from the bottom on the inner ring
(on electronic groupsets, not entering the top two cogs in inner mode) into
a potential slack-chain condition (→here).
With the same rear derailleur settings,
I switched the rear wheel to the 11–23T side.
Since this rear derailleur doesn't support this tooth count anyway,
there's a gap between the sprocket and the upper pulley,
but shifting itself works fine.
This bike currently has no shifting function
on the brake lever area.
The image above shows the only shifter,
with button A on the right side (outside) for shifting toward the top,
and button B on the left side (inside) for shifting toward the low end.
Furthermore, there's no component equivalent to the upper junction,
so shift adjustment can only be done by connecting the rear derailleur alone to the diagnostic kit
and adjusting on the PC screen.
At Shimano, the top gear side is the higher number,
so as shown in the image above, the top cog is 11,
and 1 is the low gear.
But since I've removed one tooth from the sprocket,
the low gear is now 2.
If I were removing 4 speeds from 11 (→here), that would be one thing,
but for just removing 1 speed, adjusting only the set screw on the adjuster was enough.
Even if I shift to 1, the chain won't drop inward,
but the rear derailleur works hard to get the chain into the 11-speed low gear,
the motor squeaks "meep meep meep," and it puts considerable strain on things,
so I must not press button B when it's on 2.