A customer brought in a rear wheel built with a DT XR331 rim.
It was one we built here in the shop previously.
The nipple has fractured.
This rim requires being built with a Squorx nipple + PHR washer.
Squorx nipples only come in silver and black
(red was added later),
and if you try to build a wheel with nipples in other colors
using a generic nipple + PHR washer combination,
the PHR washer is highly aggressive toward the nipple,
and fractures like in the image above can occur
in as little as two months after building.
It happened on both my customer's wheels and my own.
Because of this, I collected several pairs of wheels
that had already been built with generic nipple + PHR washer combinations
and rebuilt them for free at that time.
However, this wheel
uses Squorx nipples.
Squorx nipples
have thick contact surfaces with the washer,
so they're thought to be stronger against fracturing.
By the way, I call it "bare Squorx"
when Squorx nipples are used alone
on rims that don't require PHR washers.
Prime wheels are an example of this.
With bare Squorx, the contact with the rim hole
approaches point contact rather than surface contact,
and the friction resistance during rotation is also larger,
so I don't do it.
Looking at the spoke with the fractured nipple,
there's deformation in the direction of rotation wrap.
This is a wheel used for cyclocross, but
there were two other spokes bent in a similar pattern
separate from the fracture location.
I replaced the bent spokes
and the Squorx nipples at those locations.
I've never seen a Squorx nipple fracture before,
so from now on I'll say: "I've never seen a Squorx nipple fracture
without evidence of large external forces applied to the spoke."
↑Replaced spoke
↑Replaced nipple
It might just be speculation,
but perhaps the result was that spoke bent, tension was lost →
the nipple and the inner edge of the washer
came into contact repeatedly in a rattling motion,
causing this outcome.
It was one we built here in the shop previously.
The nipple has fractured.
This rim requires being built with a Squorx nipple + PHR washer.
Squorx nipples only come in silver and black
(red was added later),
and if you try to build a wheel with nipples in other colors
using a generic nipple + PHR washer combination,
the PHR washer is highly aggressive toward the nipple,
and fractures like in the image above can occur
in as little as two months after building.
It happened on both my customer's wheels and my own.
Because of this, I collected several pairs of wheels
that had already been built with generic nipple + PHR washer combinations
and rebuilt them for free at that time.
However, this wheel
uses Squorx nipples.
Squorx nipples
have thick contact surfaces with the washer,
so they're thought to be stronger against fracturing.
By the way, I call it "bare Squorx"
when Squorx nipples are used alone
on rims that don't require PHR washers.
Prime wheels are an example of this.
With bare Squorx, the contact with the rim hole
approaches point contact rather than surface contact,
and the friction resistance during rotation is also larger,
so I don't do it.
Looking at the spoke with the fractured nipple,
there's deformation in the direction of rotation wrap.
This is a wheel used for cyclocross, but
there were two other spokes bent in a similar pattern
separate from the fracture location.
I replaced the bent spokes
and the Squorx nipples at those locations.
I've never seen a Squorx nipple fracture before,
so from now on I'll say: "I've never seen a Squorx nipple fracture
without evidence of large external forces applied to the spoke."
↑Replaced spoke
↑Replaced nipple
It might just be speculation,
but perhaps the result was that spoke bent, tension was lost →
the nipple and the inner edge of the washer
came into contact repeatedly in a rattling motion,
causing this outcome.