Wheels again today (and so on).
I built a front wheel with an ETRTO 406mm, 20-inch HE diameter,
50mm high carbon rim.
The hub is a disassembled front wheel from a WH-S500 complete wheelset.
24 spokes, all black, #14 gauge Champion straight, double-cross lacing, forced left and right,
with black nipples.
Since the final crossing isn't woven, I don't tie the spokes,
but with the small diameter and deep rim, the spokes are extremely short
and the angles are very tight, so the spokes barely touch at the final crossing.
Jumping back in the timeline, here's the hub for this build.
The WH-S500 is a complete wheelset with a quick-release on front and nuts on the rear.
The rear wheel with a centerlock-mount internal hub gear and rim-brake-incompatible rim is the WH-S500-8D,
the version with a rim-brake-compatible rim is the WH-S500-V-8D,
the front wheel with a rim-brake-compatible rim and disc hub is the WH-S500-V-F,
its dynamo hub version is the WH-S500-V-3D,
and the version where the rim becomes rim-brake-incompatible
and becomes disc-brake-only is the WH-S500-3D.
So there are 5 different specifications across front and rear wheels combined.
Since this hub is a dynamo front hub,
the original wheel could have been one of 2 types,
but I don't know which.
On the right side, the hub dynamo connector,
and on the left side, the centerlock mount.
Actually, this front wheel is technically incompatible according to dynamo hub standards.
However, since it was a customer's bring-in job,
I had no choice but to build the wheel and did so.
I did explain the compatibility issue to the customer.
When you build a wheel with a dynamo hub designed for large-diameter wheels
on a small-diameter rim,
the hub's rotation speed at a given velocity increases,
and in some cases it can exceed the power generation capacity the hub was designed for.
Shimano dynamo hubs have varying compatibility ranges—
some are narrow at 26–28 inches,
while others are wider at 20–28 inches.
This hub is the former type, and the numbers 646–716mm
visible on the hub barrel in the image above refer to
tire diameter, not rim diameter.
When you mount road bike tires on a 622mm-diameter clincher rim and inflate them,
the diameter becomes approximately 700mm (700C),
which is why we call it 700C;
but actually, when the tire size is 25C wide,
the actual measurement is only around 670C.
The tire width needed to reach 700C on a 622C rim is about 40C.
The lower limit of 646mm on the hub barrel appears to cover
the 650C, which is the nominal size for WO (wired-on) 26-inch rims,
but it actually doesn't.
Just as 700×25C actually measures around 670C,
with 650C, even with tire widths of 23C or 25C,
the actual measurement is only around 620C.
Even with the same nominal 26-inch size, if it's an HE (hooked edge) rim
using the MTB 26-inch rim standard,
a 26×1.95 tire size
(viewed as a slick tire excluding knob height)
would be around 652C, so it would be covered.
But since 26-inch HE rims with 24 spokes are practically non-existent,
the 646–716mm range on the hub barrel
is essentially synonymous with "only compatible with so-called 700C rims."
I built a front wheel with an ETRTO 406mm, 20-inch HE diameter,
50mm high carbon rim.
The hub is a disassembled front wheel from a WH-S500 complete wheelset.
24 spokes, all black, #14 gauge Champion straight, double-cross lacing, forced left and right,
with black nipples.
Since the final crossing isn't woven, I don't tie the spokes,
but with the small diameter and deep rim, the spokes are extremely short
and the angles are very tight, so the spokes barely touch at the final crossing.
Jumping back in the timeline, here's the hub for this build.
The WH-S500 is a complete wheelset with a quick-release on front and nuts on the rear.
The rear wheel with a centerlock-mount internal hub gear and rim-brake-incompatible rim is the WH-S500-8D,
the version with a rim-brake-compatible rim is the WH-S500-V-8D,
the front wheel with a rim-brake-compatible rim and disc hub is the WH-S500-V-F,
its dynamo hub version is the WH-S500-V-3D,
and the version where the rim becomes rim-brake-incompatible
and becomes disc-brake-only is the WH-S500-3D.
So there are 5 different specifications across front and rear wheels combined.
Since this hub is a dynamo front hub,
the original wheel could have been one of 2 types,
but I don't know which.
On the right side, the hub dynamo connector,
and on the left side, the centerlock mount.
Actually, this front wheel is technically incompatible according to dynamo hub standards.
However, since it was a customer's bring-in job,
I had no choice but to build the wheel and did so.
I did explain the compatibility issue to the customer.
When you build a wheel with a dynamo hub designed for large-diameter wheels
on a small-diameter rim,
the hub's rotation speed at a given velocity increases,
and in some cases it can exceed the power generation capacity the hub was designed for.
Shimano dynamo hubs have varying compatibility ranges—
some are narrow at 26–28 inches,
while others are wider at 20–28 inches.
This hub is the former type, and the numbers 646–716mm
visible on the hub barrel in the image above refer to
tire diameter, not rim diameter.
When you mount road bike tires on a 622mm-diameter clincher rim and inflate them,
the diameter becomes approximately 700mm (700C),
which is why we call it 700C;
but actually, when the tire size is 25C wide,
the actual measurement is only around 670C.
The tire width needed to reach 700C on a 622C rim is about 40C.
The lower limit of 646mm on the hub barrel appears to cover
the 650C, which is the nominal size for WO (wired-on) 26-inch rims,
but it actually doesn't.
Just as 700×25C actually measures around 670C,
with 650C, even with tire widths of 23C or 25C,
the actual measurement is only around 620C.
Even with the same nominal 26-inch size, if it's an HE (hooked edge) rim
using the MTB 26-inch rim standard,
a 26×1.95 tire size
(viewed as a slick tire excluding knob height)
would be around 652C, so it would be covered.
But since 26-inch HE rims with 24 spokes are practically non-existent,
the 646–716mm range on the hub barrel
is essentially synonymous with "only compatible with so-called 700C rims."