A customer left a WH-7801C rear wheel with me.
The hub had gotten rough and they wanted me to fix it.
The fact that it "had gotten" rough means
there was a time when it wasn't rough.
Since the nipples are hub-side nipples...
I don't necessarily need to peel off the tubular tire, but...
There were spots where the protective film that's supposed to be removed
to allow the rim tape to settle between the tire and rim
hadn't been removed, so I decided to take the tire off.
↑The film not being fully peeled off would've been fine,
but there was something that gave me chills.
When I peeled off the tire,
there was no rim tape left on the rim side.
So was it on the tire's inner surface then? Not quite.
When I took the tire off, there were only six patches
of about 10cm of tape applied at roughly 60-degree intervals
scattered around. The forgotten film is a mistake,
but applying tape only in patches like this seems to be
done intentionally as some kind of preference.
If it's just their own equipment and they do it at their own risk, fine,
but I'd strongly recommend properly taping the entire surface
except for the valve hole.
This WH-7801C rim is from an early production batch.
Like rims from ENVE or Easton,
there's an oblong hole across from the valve hole,
and the cap covering it is aluminum on early batches.
After the early batches, this cap became carbon fiber.
This hole exists to allow removal of the rim's internal balloon.
↑This is an ENVE 25mm rim,
and the carbon fiber cap has come off.
ENVE rims are at their weakest against brake heat,
and using Swissstop Yellow King, which is arguably the worst
in terms of brake heat generation, is also a contributing factor.
The rim, retaining heat and swelling slightly,
causes the brake shoe to catch on that swelling,
which then worsens the swelling further—a vicious cycle.
In the image above, you can see how the rim's swelling
is accumulating brake shoe dust as if filtering it out.
Also, regardless of this particular rim,
the balloon hole cap's position is weak against buckling
when holding heat. If the contact point happens to be
right there when you slam down on a step or edge,
the cap can come off and either stick to the tire
when you remove it from the rim or just fall out.
I disassembled the hub.
The bearings and ball races showed no abnormalities.
After cleaning, greasing, and reassembling,
the roughness in rotation was nearly gone.
What was fortunate this time was that
the freewheel body's bearings hadn't failed.
This hub has a structure unusual for Shimano,
with hub bearings on both sides of the hub body,
but the ball spring freewheel body attached to the right side.
The cartridge bearing on the freewheel body is a standard size,
but the spacer between the outer and inner bearings
is press-fitted without any expectation of bearing replacement,
making it basically impossible to remove
the snap ring that prevents inner bearing dropout.
Even if you say "Forget replacing the bearing,
just swap out the entire freewheel body,"
spare parts supply ended long ago.
It's Shimano's usual response: "Don't cling to old Dura-Ace from n generations back—
just go buy the latest Dura-Ace already!"
but depending on the part, the number in n
can be as low as 1 (→here),
which is how ruthless Shimano can be.
In this case, n=4 for the freewheel body.
The temporary centering was almost spot-on,
and while there was minimal center deviation depending on the spoke angle,
centering came out naturally once I corrected the slight lateral runout.
Since hub-side nipples have poor workability,
I was glad the number of spoke turns needed was minimal.
The hub had gotten rough and they wanted me to fix it.
The fact that it "had gotten" rough means
there was a time when it wasn't rough.
Since the nipples are hub-side nipples...
I don't necessarily need to peel off the tubular tire, but...
There were spots where the protective film that's supposed to be removed
to allow the rim tape to settle between the tire and rim
hadn't been removed, so I decided to take the tire off.
↑The film not being fully peeled off would've been fine,
but there was something that gave me chills.
When I peeled off the tire,
there was no rim tape left on the rim side.
So was it on the tire's inner surface then? Not quite.
When I took the tire off, there were only six patches
of about 10cm of tape applied at roughly 60-degree intervals
scattered around. The forgotten film is a mistake,
but applying tape only in patches like this seems to be
done intentionally as some kind of preference.
If it's just their own equipment and they do it at their own risk, fine,
but I'd strongly recommend properly taping the entire surface
except for the valve hole.
This WH-7801C rim is from an early production batch.
Like rims from ENVE or Easton,
there's an oblong hole across from the valve hole,
and the cap covering it is aluminum on early batches.
After the early batches, this cap became carbon fiber.
This hole exists to allow removal of the rim's internal balloon.
↑This is an ENVE 25mm rim,
and the carbon fiber cap has come off.
ENVE rims are at their weakest against brake heat,
and using Swissstop Yellow King, which is arguably the worst
in terms of brake heat generation, is also a contributing factor.
The rim, retaining heat and swelling slightly,
causes the brake shoe to catch on that swelling,
which then worsens the swelling further—a vicious cycle.
In the image above, you can see how the rim's swelling
is accumulating brake shoe dust as if filtering it out.
Also, regardless of this particular rim,
the balloon hole cap's position is weak against buckling
when holding heat. If the contact point happens to be
right there when you slam down on a step or edge,
the cap can come off and either stick to the tire
when you remove it from the rim or just fall out.
I disassembled the hub.
The bearings and ball races showed no abnormalities.
After cleaning, greasing, and reassembling,
the roughness in rotation was nearly gone.
What was fortunate this time was that
the freewheel body's bearings hadn't failed.
This hub has a structure unusual for Shimano,
with hub bearings on both sides of the hub body,
but the ball spring freewheel body attached to the right side.
The cartridge bearing on the freewheel body is a standard size,
but the spacer between the outer and inner bearings
is press-fitted without any expectation of bearing replacement,
making it basically impossible to remove
the snap ring that prevents inner bearing dropout.
Even if you say "Forget replacing the bearing,
just swap out the entire freewheel body,"
spare parts supply ended long ago.
It's Shimano's usual response: "Don't cling to old Dura-Ace from n generations back—
just go buy the latest Dura-Ace already!"
but depending on the part, the number in n
can be as low as 1 (→here),
which is how ruthless Shimano can be.
In this case, n=4 for the freewheel body.
The temporary centering was almost spot-on,
and while there was minimal center deviation depending on the spoke angle,
centering came out naturally once I corrected the slight lateral runout.
Since hub-side nipples have poor workability,
I was glad the number of spoke turns needed was minimal.