Another wheel building day (and so on).
A customer entrusted me with front and rear wheels
built with Chinese carbon rims.
Today I'm only working on the rear wheel though.
The hub is a 24-hole disc hub with straight spokes and high-low flanges,
and the spokes are Pillar square aero spokes.
With this wheel's nipples,
failures below the head have occurred in two locations.
The spokes on this wheel are Pillar-made.
There's a stamp on them, so there's no doubt.
The nipples are definitely not DT or Sapim,
so they must be Pillar nipples.
I almost never use the 14mm aluminum nipples
that come with Sapim's CX-RAY,
because from my experience, I know that
aluminum nipples from manufacturers other than DT
have significantly higher chances of experiencing
failures below the head like this one compared to DT.
If you've only built one or two wheels, you won't notice,
but once you've built 100 or 200,
the difference becomes clear.
Of course, DT nipples won't absolutely never experience
failures below the head either.
Another reason I don't use Sapim's silver aluminum nipples
is that they tend to develop white rust.
Actually, both the front and rear wheels this time
have a history of broken nipple replacements done at our shop.
This time, if I just patch the broken spots with
DT aluminum nipples as a makeshift measure,
those spots probably won't fail again afterwards,
but the customer said the distrust can't be erased,
so we decided to replace all the nipples.
Since we're doing the same work as wheel building anyway,
they requested that we change the spoke gauge on one side
and do an asymmetric build with bracing.
↑The broken ones
The cause of the failures: the spoke length being too short is a major factor.
If the spokes reached flush with the rim on the nipple end,
the load per thread of spoke tension received by the thread depth
would be quite different.
To be clear, I can state that Pillar's nipples having "poor quality"
is an element, but
in this case, the short spoke length is actually
the major factor in the failures.
If the spokes were just a bit longer,
we probably wouldn't have had failures this frequently.
↑The nipple on the right side of the image has short protrusion from the rim,
this is the spot we patched with a DT nipple.
Hmm, hard to photograph well.
Regarding spoke length, on both sides
the spokes were just barely long enough to reach the nipple slot.
With DT nipples, spokes of that length wouldn't
fail frequently, so the strength quality of the nipples themselves
does matter.
↑These are the original unbroken nipples,
and it's funny how the shape below the head is thick,
looking resistant to failure.
The spokes have different butted start positions left and right,
but they're the same gauge.
The length difference was 4mm.
This is because it's a high-low flange hub.
If it were a hub with equal-diameter flanges on both sides,
the difference would be around 2.5mm.
The specific lengths are 286mm and 290mm.
For spoke specific gravity, 12 spokes at 286mm weighing 85.6g,
so 85.6÷12÷286÷0.0257 = 0.970495..., which means
the 12 spokes at 290mm weigh 87.1g, so
87.1÷12÷290÷0.0257 = 0.973880...,
so we can say about 97%.
Spoke specific gravity is information you need to know
when building asymmetric wheels.
I can't believe no one proposed this important concept
before me.
If these spokes were just 2mm longer on both sides,
they'd be just right, so
I cut the non-drive side from 290mm down to
288mm and reused it on the drive side,
and built the non-drive side with 292mm CX-RAY straight spokes.
The asymmetric difference is almost a half-campagnolo offset, but
CX Sprint might have worked for the non-drive side too.
Also, with the asymmetric building bonus,
the thread wrap-around on the non-drive spokes increases,
so 291mm would have worked instead of 292mm.
Rebuilt.
Drive side is Pillar square aero,
non-drive side is CX-RAY,
forced 2-cross build on both sides.
The bracing comes later.
Both sides have the final crossover woven,
which matches the original wheel's configuration.
A customer entrusted me with front and rear wheels
built with Chinese carbon rims.
Today I'm only working on the rear wheel though.
The hub is a 24-hole disc hub with straight spokes and high-low flanges,
and the spokes are Pillar square aero spokes.
With this wheel's nipples,
failures below the head have occurred in two locations.
The spokes on this wheel are Pillar-made.
There's a stamp on them, so there's no doubt.
The nipples are definitely not DT or Sapim,
so they must be Pillar nipples.
I almost never use the 14mm aluminum nipples
that come with Sapim's CX-RAY,
because from my experience, I know that
aluminum nipples from manufacturers other than DT
have significantly higher chances of experiencing
failures below the head like this one compared to DT.
If you've only built one or two wheels, you won't notice,
but once you've built 100 or 200,
the difference becomes clear.
Of course, DT nipples won't absolutely never experience
failures below the head either.
Another reason I don't use Sapim's silver aluminum nipples
is that they tend to develop white rust.
Actually, both the front and rear wheels this time
have a history of broken nipple replacements done at our shop.
This time, if I just patch the broken spots with
DT aluminum nipples as a makeshift measure,
those spots probably won't fail again afterwards,
but the customer said the distrust can't be erased,
so we decided to replace all the nipples.
Since we're doing the same work as wheel building anyway,
they requested that we change the spoke gauge on one side
and do an asymmetric build with bracing.
↑The broken ones
The cause of the failures: the spoke length being too short is a major factor.
If the spokes reached flush with the rim on the nipple end,
the load per thread of spoke tension received by the thread depth
would be quite different.
To be clear, I can state that Pillar's nipples having "poor quality"
is an element, but
in this case, the short spoke length is actually
the major factor in the failures.
If the spokes were just a bit longer,
we probably wouldn't have had failures this frequently.
↑The nipple on the right side of the image has short protrusion from the rim,
this is the spot we patched with a DT nipple.
Hmm, hard to photograph well.
Regarding spoke length, on both sides
the spokes were just barely long enough to reach the nipple slot.
With DT nipples, spokes of that length wouldn't
fail frequently, so the strength quality of the nipples themselves
does matter.
↑These are the original unbroken nipples,
and it's funny how the shape below the head is thick,
looking resistant to failure.
The spokes have different butted start positions left and right,
but they're the same gauge.
The length difference was 4mm.
This is because it's a high-low flange hub.
If it were a hub with equal-diameter flanges on both sides,
the difference would be around 2.5mm.
The specific lengths are 286mm and 290mm.
For spoke specific gravity, 12 spokes at 286mm weighing 85.6g,
so 85.6÷12÷286÷0.0257 = 0.970495..., which means
the 12 spokes at 290mm weigh 87.1g, so
87.1÷12÷290÷0.0257 = 0.973880...,
so we can say about 97%.
Spoke specific gravity is information you need to know
when building asymmetric wheels.
I can't believe no one proposed this important concept
before me.
If these spokes were just 2mm longer on both sides,
they'd be just right, so
I cut the non-drive side from 290mm down to
288mm and reused it on the drive side,
and built the non-drive side with 292mm CX-RAY straight spokes.
The asymmetric difference is almost a half-campagnolo offset, but
CX Sprint might have worked for the non-drive side too.
Also, with the asymmetric building bonus,
the thread wrap-around on the non-drive spokes increases,
so 291mm would have worked instead of 292mm.
Rebuilt.
Drive side is Pillar square aero,
non-drive side is CX-RAY,
forced 2-cross build on both sides.
The bracing comes later.
Both sides have the final crossover woven,
which matches the original wheel's configuration.