The Niner gravel bike I'm riding has been equipped with Nomu Lab wheels #8 on both front and rear from the beginning.
The front hub happens to be a spare (→here)
It's a takeoff front hub from WH-R8170, but
I noticed the rotation had become gritty,
so I sourced the front hub complete set shown in the image above.
Cup & cone wear and
cartridge bearing damage
rarely progress at the same rate on both sides—
almost always one side deteriorates
more severely than the other.
In my front wheel's case,
one side's retainer ball bearings
had turned from silver to a rusty brown color,
and both the cup and cone showed damage.
The other side was almost undamaged.
Given that situation,
I sourced the parts shown in the image above,
which consists of the hub body plus "everything except" the left and right cups that are pressed in.
So the damaged cup couldn't be replaced,
and even after the parts swap,
a faint gritty sensation remained in the hub rotation.
That's when I noticed something:
The hub body's design relative to the pressed-in cup clearly has a "drift-out clearance" provided.
The image above shows the cup from the side without wear,
and the punch is there just to indicate the drift-out clearance—
it's not the actual tool used for pressing out.
The images up to this point were shot on April 23, 2024
for an article in the gravel bike first-year series!
Even though it says "first-year," we're already in the second year, but never mind that.
From here on the content is unrelated to my own bike,
but I'll categorize the post accordingly.
The front wheel, paired with the rear wheel I reassembled yesterday,
was placed in the truing stand for inspection,
and the hub axle wouldn't turn at all.
These were front and rear wheels used in cyclocross—
I had to reassemble the rear because the rim cracked, but
the front seemed like it would only need a truing check,
except it hadn't been used since the season ended
and the bearing area had rusted and seized up.
I put a hub wrench on the end nut
and with a forceful crack! released the rust,
and after that it did rotate, though extremely gritty.
The image above shows it after I'd removed all the parts entirely.
The cup has pitting damage.
At that point I recalled the drift-out clearance on my WH-R8170 front hub
and checked the cup dimensions,
which gave me confidence they were the same, so
I extracted a cup from the unused front hub,
a takeoff from a new wheel.
I tackled this one first because
I was concerned that the cup's press-fit was so tight
that forcing it out might damage the hub body or cause other issues.
In reality it came out pretty easily.
I also removed the cup from the RS770 hub.
I pressed the WH-R8170 hub's cup into the RS770 hub.
This is on the right side, as you can see, where there's no center-lock disc mount
but there is a double nut for the hub wrench.
That part too was the same size (though a different color),
so I also transplanted the WH-R8170 hub's right retainer bearing
and right cone plus end nut.
The left side wasn't completely undamaged,
but it didn't warrant parts replacement,
so I dealt with it through cleaning and re-greasing.
Most of you reading this far have probably already figured it out, but
Shimano does not supply this hub-side cup as a spare part.
With older Shimano hubs,
the hub body's design had the surface completely supporting the pressed-in cup,
so it wasn't designed for cup removal and reinstallation.
But this hub is different.
With Campagnolo wheels, for example,
mid-range and higher models that use cup & cone bearings
allow for cup replacement,
and even non-CULT wheels can be converted to CULT.
There are wheels that could be saved by replacing just one cup,
and the design does allow for removal and installation,
so why not sell it as a spare part?
"At least until pitting develops on one side of the cup,
the hub can deliver its peak performance—
beyond that point, it becomes absolutely impossible to restore to peak performance
within the scope of official support."
I think that's a bit ridiculous.
Additionally, and I say this with conviction though it's personal observation:
Shimano wheels, especially Dura-Ace grade wheels,
have mismatched durability between rim and hub—
I've frequently seen cases through the 9000 series where
the rim was falling apart while
the hub was essentially trouble-free with no maintenance.
But the R9100 series hubs and later seem to have
lower durability than earlier hubs.
I've even rebuilt a WH-R8170 front wheel that we didn't sell at our shop
with a Revolver disc hub because the hub rotation was gritty,
and just the other day I rebuilt a front-rear pair where
one of two WH-R9270 front wheels became the rear,
because that front hub's rotation was gritty too,
so I rebuilt it with a takeoff front hub.
If I'd experienced a cup replacement case at that time,
the wheel rebuild might not have been necessary.
That WH-R9270 was tubular-spec
and not regularly ridden, with almost no wet-weather use.
The hub had no play in the bearing preload
and hadn't been retightened afterward.
For the usage pattern, its short lifespan was puzzling.
After the swap, I had the original R9270 hub go home with the customer
because one side's damage was progressing extremely faster than the other.
In the future, when pitting develops in one of the swapped hub's cups
and it becomes more damaged than the better side of the original hub,
even replacing just that one cup will help—
so it serves as a source of parts for that.
↑Parts replaced for the RS770 front hub matter
The seals viewed from the inside.
The one on the right is new for comparison,
and this part alone (though we did replace it)
could be reused after cleaning.
Retainer ball bearing
The part combining cone and double nut into one assembly
The cup extracted from the hub
If you're unhappy that replacing everything but the cup
can't restore it to like-new performance,
then buy a new hub or wheel—that's
Shimano's official position now, and likely will remain so.
The unused WH-R8170 front hub we have in stock
will be put toward rescuing WH-R8170 wheels
and RS770 hubs that we've sold in the past,
using cups and other parts to whatever extent possible.
The front hub happens to be a spare (→here)
It's a takeoff front hub from WH-R8170, but
I noticed the rotation had become gritty,
so I sourced the front hub complete set shown in the image above.
Cup & cone wear and
cartridge bearing damage
rarely progress at the same rate on both sides—
almost always one side deteriorates
more severely than the other.
In my front wheel's case,
one side's retainer ball bearings
had turned from silver to a rusty brown color,
and both the cup and cone showed damage.
The other side was almost undamaged.
Given that situation,
I sourced the parts shown in the image above,
which consists of the hub body plus "everything except" the left and right cups that are pressed in.
So the damaged cup couldn't be replaced,
and even after the parts swap,
a faint gritty sensation remained in the hub rotation.
That's when I noticed something:
The hub body's design relative to the pressed-in cup clearly has a "drift-out clearance" provided.
The image above shows the cup from the side without wear,
and the punch is there just to indicate the drift-out clearance—
it's not the actual tool used for pressing out.
The images up to this point were shot on April 23, 2024
for an article in the gravel bike first-year series!
Even though it says "first-year," we're already in the second year, but never mind that.
From here on the content is unrelated to my own bike,
but I'll categorize the post accordingly.
The front wheel, paired with the rear wheel I reassembled yesterday,
was placed in the truing stand for inspection,
and the hub axle wouldn't turn at all.
These were front and rear wheels used in cyclocross—
I had to reassemble the rear because the rim cracked, but
the front seemed like it would only need a truing check,
except it hadn't been used since the season ended
and the bearing area had rusted and seized up.
I put a hub wrench on the end nut
and with a forceful crack! released the rust,
and after that it did rotate, though extremely gritty.
The image above shows it after I'd removed all the parts entirely.
The cup has pitting damage.
At that point I recalled the drift-out clearance on my WH-R8170 front hub
and checked the cup dimensions,
which gave me confidence they were the same, so
I extracted a cup from the unused front hub,
a takeoff from a new wheel.
I tackled this one first because
I was concerned that the cup's press-fit was so tight
that forcing it out might damage the hub body or cause other issues.
In reality it came out pretty easily.
I also removed the cup from the RS770 hub.
I pressed the WH-R8170 hub's cup into the RS770 hub.
This is on the right side, as you can see, where there's no center-lock disc mount
but there is a double nut for the hub wrench.
That part too was the same size (though a different color),
so I also transplanted the WH-R8170 hub's right retainer bearing
and right cone plus end nut.
The left side wasn't completely undamaged,
but it didn't warrant parts replacement,
so I dealt with it through cleaning and re-greasing.
Most of you reading this far have probably already figured it out, but
Shimano does not supply this hub-side cup as a spare part.
With older Shimano hubs,
the hub body's design had the surface completely supporting the pressed-in cup,
so it wasn't designed for cup removal and reinstallation.
But this hub is different.
With Campagnolo wheels, for example,
mid-range and higher models that use cup & cone bearings
allow for cup replacement,
and even non-CULT wheels can be converted to CULT.
There are wheels that could be saved by replacing just one cup,
and the design does allow for removal and installation,
so why not sell it as a spare part?
"At least until pitting develops on one side of the cup,
the hub can deliver its peak performance—
beyond that point, it becomes absolutely impossible to restore to peak performance
within the scope of official support."
I think that's a bit ridiculous.
Additionally, and I say this with conviction though it's personal observation:
Shimano wheels, especially Dura-Ace grade wheels,
have mismatched durability between rim and hub—
I've frequently seen cases through the 9000 series where
the rim was falling apart while
the hub was essentially trouble-free with no maintenance.
But the R9100 series hubs and later seem to have
lower durability than earlier hubs.
I've even rebuilt a WH-R8170 front wheel that we didn't sell at our shop
with a Revolver disc hub because the hub rotation was gritty,
and just the other day I rebuilt a front-rear pair where
one of two WH-R9270 front wheels became the rear,
because that front hub's rotation was gritty too,
so I rebuilt it with a takeoff front hub.
If I'd experienced a cup replacement case at that time,
the wheel rebuild might not have been necessary.
That WH-R9270 was tubular-spec
and not regularly ridden, with almost no wet-weather use.
The hub had no play in the bearing preload
and hadn't been retightened afterward.
For the usage pattern, its short lifespan was puzzling.
After the swap, I had the original R9270 hub go home with the customer
because one side's damage was progressing extremely faster than the other.
In the future, when pitting develops in one of the swapped hub's cups
and it becomes more damaged than the better side of the original hub,
even replacing just that one cup will help—
so it serves as a source of parts for that.
↑Parts replaced for the RS770 front hub matter
The seals viewed from the inside.
The one on the right is new for comparison,
and this part alone (though we did replace it)
could be reused after cleaning.
Retainer ball bearing
The part combining cone and double nut into one assembly
The cup extracted from the hub
If you're unhappy that replacing everything but the cup
can't restore it to like-new performance,
then buy a new hub or wheel—that's
Shimano's official position now, and likely will remain so.
The unused WH-R8170 front hub we have in stock
will be put toward rescuing WH-R8170 wheels
and RS770 hubs that we've sold in the past,
using cups and other parts to whatever extent possible.