I received some comments, so here's my response.
I've written many times on this blog that "what matters for wheel lightness is the outer diameter section."
So does hub weight reduction have no meaning?
It's just that it's not as important as the outer section for acceleration performance.
If hub rotational performance is the same, of course lighter is always better.
One thing I can't understand is
"using the total weight of front and rear wheels listed in catalog specs
as the basis for choosing (buying) wheels."
Like saying "that wheel from such-and-such is 1500g"
and comparing it to other wheels' totals.
With a front and rear total of 1500g wheels,
the distribution is roughly 650g for the front and 850g for the rear.
This "650g front wheel" information doesn't really mean much to me.
What really matters is how much the rim weighs.
I don't have space to give many examples, but for instance, with Mavic:
the 1999 original Ksyrium WO front rim is 510g,
the 2010 Cosmic Carbone SL WO front rim is 542g,
the 2011 Ksyrium K10 WO front rim is 392g,
and the 2012 R-SYS Premium WO front rim is 385g.
The Open Pro WO rim is around 440g for the black finish depending on the year.
(Spoke count doesn't affect weight much, but rim color and surface treatment have a big impact.)
All of these are my personal measurements.
I felt articles without images looked lonely,
so I stuck in an irrelevant picture. It has nothing to do with the text.
For example, if you build a 28H and 36H Open Pro with the same hub and spokes,
depending on the spokes, the 36H wheel will be over 50g heavier.
If that's the front wheel, there's a big difference in impression between "actual measurement 750g" and "actual measurement 805g,"
but if the rim weight is the same, you get wheels with roughly the same acceleration performance,
so the correct evaluation is to view these as "wheels with a 440g rim" rather than being fooled by
the surface information of "700g-class wheel" or "800g-class wheel."
However, most people don't often get the chance to disassemble complete wheels.
I don't think I went too far, but
I have actually sourced complete wheels, immediately disassembled them and documented them, then even modified them
(→here).
Complete wheels are "off-the-rack wheels for unknown users in unknown situations,"
so they build in quite large safety margins for strength. Because of this, the rims can't be made too light.
Spokes in most cases are straight spokes, but with high-strength rims
tensioned really high, you can use fewer spokes.
Hubs can be custom-designed, so non-critical parts for strength can be radically lightened.
In other words, compared to hand-built wheels, there's a strong tendency for the outer section to be heavy and the inner section to be light.
The R-SYS Premium has a front rim of 385g, which becomes 595g as a complete wheel.
That's rim plus 210g to make a wheel—this is impossible with hand-built materials.
Complete wheels tend to strongly show themselves as lighter on paper by reducing weight in areas that have little positive impact on riding performance, especially acceleration performance.
To put it extremely, if the R-SYS front hub became 100g heavier,
I think you'd barely notice it on flat ground riding.
But if the rim became 100g heavier, you'd have a wheel that doesn't perform.
I wrote earlier that hub weight, lighter is always better.
There are people who climb over 20km of the Norikura hill climb in about an hour,
but if you're told "get from the Norikura start to the finish
faster using only human power and a machine with no motor,"
"ride a road bike" is humanity's optimal answer.
While being helped by the bike itself, you're also carrying the bike as cargo up the mountain,
so naturally a lighter bike itself is advantageous.
There's a hub called GOKISO.
The rear hub's catalog weight is 455g, actual measurement 447g, and
it's characterized by extremely low-resistance rotation performance.
This is heavier than a PowerTap SL+ rear hub (actual measurement 426g), but
when it gets this heavy, even with such a smooth-rolling hub, it gets a bit concerning.
Hub weight isn't much of a concern on flat ground,
but on climbs it's advantageous to be light just like other parts of the bike,
so lighter is always better—that's my conclusion.
I've written many times on this blog that "what matters for wheel lightness is the outer diameter section."
So does hub weight reduction have no meaning?
It's just that it's not as important as the outer section for acceleration performance.
If hub rotational performance is the same, of course lighter is always better.
One thing I can't understand is
"using the total weight of front and rear wheels listed in catalog specs
as the basis for choosing (buying) wheels."
Like saying "that wheel from such-and-such is 1500g"
and comparing it to other wheels' totals.
With a front and rear total of 1500g wheels,
the distribution is roughly 650g for the front and 850g for the rear.
This "650g front wheel" information doesn't really mean much to me.
What really matters is how much the rim weighs.
I don't have space to give many examples, but for instance, with Mavic:
the 1999 original Ksyrium WO front rim is 510g,
the 2010 Cosmic Carbone SL WO front rim is 542g,
the 2011 Ksyrium K10 WO front rim is 392g,
and the 2012 R-SYS Premium WO front rim is 385g.
The Open Pro WO rim is around 440g for the black finish depending on the year.
(Spoke count doesn't affect weight much, but rim color and surface treatment have a big impact.)
All of these are my personal measurements.
I felt articles without images looked lonely,
so I stuck in an irrelevant picture. It has nothing to do with the text.
For example, if you build a 28H and 36H Open Pro with the same hub and spokes,
depending on the spokes, the 36H wheel will be over 50g heavier.
If that's the front wheel, there's a big difference in impression between "actual measurement 750g" and "actual measurement 805g,"
but if the rim weight is the same, you get wheels with roughly the same acceleration performance,
so the correct evaluation is to view these as "wheels with a 440g rim" rather than being fooled by
the surface information of "700g-class wheel" or "800g-class wheel."
However, most people don't often get the chance to disassemble complete wheels.
I don't think I went too far, but
I have actually sourced complete wheels, immediately disassembled them and documented them, then even modified them
(→here).
Complete wheels are "off-the-rack wheels for unknown users in unknown situations,"
so they build in quite large safety margins for strength. Because of this, the rims can't be made too light.
Spokes in most cases are straight spokes, but with high-strength rims
tensioned really high, you can use fewer spokes.
Hubs can be custom-designed, so non-critical parts for strength can be radically lightened.
In other words, compared to hand-built wheels, there's a strong tendency for the outer section to be heavy and the inner section to be light.
The R-SYS Premium has a front rim of 385g, which becomes 595g as a complete wheel.
That's rim plus 210g to make a wheel—this is impossible with hand-built materials.
Complete wheels tend to strongly show themselves as lighter on paper by reducing weight in areas that have little positive impact on riding performance, especially acceleration performance.
To put it extremely, if the R-SYS front hub became 100g heavier,
I think you'd barely notice it on flat ground riding.
But if the rim became 100g heavier, you'd have a wheel that doesn't perform.
I wrote earlier that hub weight, lighter is always better.
There are people who climb over 20km of the Norikura hill climb in about an hour,
but if you're told "get from the Norikura start to the finish
faster using only human power and a machine with no motor,"
"ride a road bike" is humanity's optimal answer.
While being helped by the bike itself, you're also carrying the bike as cargo up the mountain,
so naturally a lighter bike itself is advantageous.
There's a hub called GOKISO.
The rear hub's catalog weight is 455g, actual measurement 447g, and
it's characterized by extremely low-resistance rotation performance.
This is heavier than a PowerTap SL+ rear hub (actual measurement 426g), but
when it gets this heavy, even with such a smooth-rolling hub, it gets a bit concerning.
Hub weight isn't much of a concern on flat ground,
but on climbs it's advantageous to be light just like other parts of the bike,
so lighter is always better—that's my conclusion.