This time, I'm writing about the spokes from BERD (ベルド) that I used to build a wheel with a Duke rim.
These are polyethylene spokes, or to be more precise, ultra-high-molecular-weight polyethylene, which in most cases refers to Dyneema, a trademark of the Dutch company DSM. BERD explicitly states that the non-metal portions of their spokes are made of Dyneema.
The threaded end of the spoke has a steel spoke segment bonded to it,
The metal portion is about 65mm, and the bonded length is about 45mm. Beyond that, it's all made of Dyneema,
On the hub side, this loop is threaded through the flange hole,
↑and a rod (a bar-shaped part) is inserted into the loop, then fixed by pulling with spoke tension. When spoke tension is applied, this rod gets compressed in the middle like a pillow, so it won't slip out of the loop.
In the case of hub flanges for J-bend spokes, the area around the hole needs to be precisely ground smooth, which is an irreversible modification. After that, you can no longer build wheels with steel spokes on that hub.
For tangent-laced straight-pull spokes, you normally need to use an aluminum bead-like part called a Tangential Straight-Pull Insert, but the Extra-Light hub from my previous article is designed to work with BERD spokes, so no insert is needed. Later on, you can also build wheels with steel straight-pull spokes.
Itano Circus
BERD spokes are often mistakenly referred to as Spinergy Zyron spokes, so I'll clarify the differences. The image above shows Zyron spokes.
There are different spoke diameters depending on the application—road, MTB, wheelchair, and so on.
↑Zyron spokes can be bent like this, but
their bending limit is about here. If you compress them more than this, they develop a crease.
The crease issue is with the outer covering. The fibers inside probably don't break.
With BERD spokes, however, even when folded in half, they don't develop creases. The spoke is hollow, with a sock-like structure.
↑This is a bag of 300mm spokes, 17 pieces. When I looked into what BERD means by "spoke length,"
it's to the end of the loop. They look shorter than 300mm, but if you pull them they'll reach about 300mm. And crucially, these spokes actually stretch noticeably under tension at first. The day after building a wheel, the tension will slacken, the wheel develops runout, and sometimes the center shifts. Building wheels with these requires technique, and there are hidden pitfalls you can't foresee beforehand (the manufacturer has various warnings, but the wording is imprecise).
Let me check the spoke specific gravity. 17 pieces of 300mm spokes weigh 42.9g, so 42.9÷17÷300÷0.0257 equals approximately 0.327305, which gives us about 32-33%. Sapim CX-RAY comes in at approximately 65%, or more precisely 64.5%, so you could say these are "roughly half the weight of CX-RAY."
However, these spokes aren't made of a single material. As I mentioned earlier, the threaded end is about 65mm of steel spoke. It's a #14 plain with a flattening (crushing) to prevent the spoke from twisting when the nipple is turned. Calculating the weight of this steel portion: 0.0257×65×17 = 28.3985g. So of the 42.9g shown in the image above, about 28.4g is the metal portion, and the remaining 14.5g is Dyneema.
Composed of two materials with extreme weight differences—not a single material—the spoke length only varies with the lighter material, and as spokes get shorter, the proportion of the heavier material increases, so the specific gravity grows. But in the 250-300mm range that might be used on 700C rims, it's fair to say, as I mentioned, that they're "about half the weight of CX-RAY," and that's quite accurate.
One last thing. A customer who knows a lot about carbon, epoxy, adhesives, and related materials came in today—he's the regular we call the "green nipple guy" because he always praises wheels built with green nipples whenever they appear in this blog—and he taught me various things about Dyneema. Separately, I received a comment about the BERD wheel I wrote about the other day, specifically regarding how I didn't cross all the spokes per BERD's instructions. I'll paste his comment verbatim below:
Dyneema (ultra-high-molecular-weight PE) is said to be weak to abrasion, so the instruction is probably to avoid spoke-to-spoke rubbing. Among super fibers like Kevlar (and similar products like Twaron) and Vectran, Dyneema has probably the highest tensile strength per unit weight, but unlike the others, it's extremely weak to heat (being polyethylene after all), so its applications are limited.
These are polyethylene spokes, or to be more precise, ultra-high-molecular-weight polyethylene, which in most cases refers to Dyneema, a trademark of the Dutch company DSM. BERD explicitly states that the non-metal portions of their spokes are made of Dyneema.
The threaded end of the spoke has a steel spoke segment bonded to it,
The metal portion is about 65mm, and the bonded length is about 45mm. Beyond that, it's all made of Dyneema,
On the hub side, this loop is threaded through the flange hole,
↑and a rod (a bar-shaped part) is inserted into the loop, then fixed by pulling with spoke tension. When spoke tension is applied, this rod gets compressed in the middle like a pillow, so it won't slip out of the loop.
In the case of hub flanges for J-bend spokes, the area around the hole needs to be precisely ground smooth, which is an irreversible modification. After that, you can no longer build wheels with steel spokes on that hub.
For tangent-laced straight-pull spokes, you normally need to use an aluminum bead-like part called a Tangential Straight-Pull Insert, but the Extra-Light hub from my previous article is designed to work with BERD spokes, so no insert is needed. Later on, you can also build wheels with steel straight-pull spokes.
Itano Circus
BERD spokes are often mistakenly referred to as Spinergy Zyron spokes, so I'll clarify the differences. The image above shows Zyron spokes.
There are different spoke diameters depending on the application—road, MTB, wheelchair, and so on.
↑Zyron spokes can be bent like this, but
their bending limit is about here. If you compress them more than this, they develop a crease.
The crease issue is with the outer covering. The fibers inside probably don't break.
With BERD spokes, however, even when folded in half, they don't develop creases. The spoke is hollow, with a sock-like structure.
↑This is a bag of 300mm spokes, 17 pieces. When I looked into what BERD means by "spoke length,"
it's to the end of the loop. They look shorter than 300mm, but if you pull them they'll reach about 300mm. And crucially, these spokes actually stretch noticeably under tension at first. The day after building a wheel, the tension will slacken, the wheel develops runout, and sometimes the center shifts. Building wheels with these requires technique, and there are hidden pitfalls you can't foresee beforehand (the manufacturer has various warnings, but the wording is imprecise).
Let me check the spoke specific gravity. 17 pieces of 300mm spokes weigh 42.9g, so 42.9÷17÷300÷0.0257 equals approximately 0.327305, which gives us about 32-33%. Sapim CX-RAY comes in at approximately 65%, or more precisely 64.5%, so you could say these are "roughly half the weight of CX-RAY."
However, these spokes aren't made of a single material. As I mentioned earlier, the threaded end is about 65mm of steel spoke. It's a #14 plain with a flattening (crushing) to prevent the spoke from twisting when the nipple is turned. Calculating the weight of this steel portion: 0.0257×65×17 = 28.3985g. So of the 42.9g shown in the image above, about 28.4g is the metal portion, and the remaining 14.5g is Dyneema.
Composed of two materials with extreme weight differences—not a single material—the spoke length only varies with the lighter material, and as spokes get shorter, the proportion of the heavier material increases, so the specific gravity grows. But in the 250-300mm range that might be used on 700C rims, it's fair to say, as I mentioned, that they're "about half the weight of CX-RAY," and that's quite accurate.
One last thing. A customer who knows a lot about carbon, epoxy, adhesives, and related materials came in today—he's the regular we call the "green nipple guy" because he always praises wheels built with green nipples whenever they appear in this blog—and he taught me various things about Dyneema. Separately, I received a comment about the BERD wheel I wrote about the other day, specifically regarding how I didn't cross all the spokes per BERD's instructions. I'll paste his comment verbatim below:
Dyneema (ultra-high-molecular-weight PE) is said to be weak to abrasion, so the instruction is probably to avoid spoke-to-spoke rubbing. Among super fibers like Kevlar (and similar products like Twaron) and Vectran, Dyneema has probably the highest tensile strength per unit weight, but unlike the others, it's extremely weak to heat (being polyethylene after all), so its applications are limited.