Jim’s Tech Talk
By Jim Langley
Berd probably won’t appreciate their revolutionary polymer spokes being referred to as “strings.” But, if you get a chance to hold a few, I think you’ll agree that they’re just as flexible and floppy as thick pieces of string – and entirely unlike the stiff stainless-steel spokes that all bicycle wheels have been built with for almost 150 years.
Berd spokes are actually made of a space-age fabric comprised of many tiny strands braided together. Berd isn’t the first to think of using a string-like material for spokes. You may have heard of the FiberFix emergency spoke, which has been around for many years – if my memory serves, I think since the early 1990’s.
That spoke is made of Kevlar and designed to make it easy to fix a broken spoke on the road or trail without removing the wheel or cassette – if you’re lucky. The flexible spoke fits in a little tube so you can tuck it in your seat bag. You can learn more and purchase the FiberFix here: https://amzn.to/2CUWCQR.
Superlight
Berd’s spokes are not for emergency use, quite the contrary. They’re designed as cycling game-changers. They take wheel weights and maybe wheel compliance, too (shock absorption) to entirely new levels. Berd spokes weigh an amazing 2.5 grams each, compared to about 4 grams for the lightest stainless-steel spokes, such as 14/17 double-butted models.
This means that depending on spoke length and what steel spokes you’re comparing them to, switching to Berds can save from 100 to 200 grams per wheelset. That pushes the envelope for building superlight wheels to impressive new levels.
And it allows building aluminum rim wheels that are as light as carbon wheels that have steel spokes – as a way to get the weight of carbon with the durability of aluminum. Plus, a set of Berd spokes costs less than most carbon rim sets (Berds cost $8 each). Berd spokes work with J-bend and straight-pull hubs.
High-tech Material
Quoting Berd, their spokes “are made from an advanced polymer called ultra high molecular weight polyethylene (UHMWPE). UHMWPE has 12 times the strength-to-weight ratio of steel and floats on water. It also has a significantly improved fatigue life and is impervious to the elements. This is what makes Berd spokes the lightest, strongest, and most durable spoke ever invented.”
I had not heard of UHMWPE, but I’ve heard of another super tough fabric called Dyneema that’s used to make Spurcycle’s Multi Pouch, which I reviewed here and have found to be super strong.
My friend Tony, a gear guru at REI who I ride with, is familiar with UHMWPE and Dyneema and tells me that it’s used in many backpacking products now and wears like iron. He’s so excited about the Berd spokes, he’s having them build him some custom wheels. You can, too, here: https://berdspokes.com/collections/berd-wheels/products/custom-wheel-building.
Durability
I wondered about the abrasion resistance of the spokes. For example, if you bend your derailleur hanger, don’t notice and then shift into the spokes? I asked Berd about that very scenario and they told me that the UHMWPE is strong enough to hold up to almost anything.
They said that the thing that would put the spokes at risk of breaking is two sharp edges coming together to cut the spokes, like scissors or diagonal cutters. But, for blows or strikes or rubbing, the spokes can take it.
Improved Ride Quality?
I haven’t had a chance to spend any time on the one set of Berd spoke wheels I’ve built so far (they belong to another guy here at work). And they’re mountain bike wheels anyway. With an MTB’s fat tires and low pressures, I wouldn’t expect to feel a big difference.
On deck to be built though, is a pair of 24-spoke carbon disc road wheels. Once those are ready I should get a chance to feel if Berd’s polymer spokes soak up road vibration better than steel the way they say – and some of their reviews, say they do. Gravel riders would love wheels that ride more smoothly – as would roadies for more comfort on rough pavement.
Two Observations So Far
Only a handful of people have seen the wheels I just finished which feature the white Berd spokes. A few of them pointed out that white polymer spokes might get dirty fast. Maybe being a synthetic material they can be cleaned with soap and water? I’m not sure. Though they’re not shown on their website, I’ve heard that the spokes are also available in black. If dirt is a concern that will probably be the wiser choice.
The other observation is that Berd’s round and bulky in places spokes (like at the hubs) are a complete departure from the aero and bladed metal spokes that are all the rage now on so many road wheelsets. That may make them less appealing to some riders mostly concerned with free speed. But there are plenty of roadies who would love to have much lighter wheels for conquering the climbs.
Building Wheels with Berd Spokes
In the photo is the build tool kit that you purchase from Berd in order to be able to prepare the hubs and pull their spokes through the hub spoke holes. Included is a tool for holding the spoke to stretch it and to prevent it twisting during wheel truing and tensioning (it’s the rectangular tool with the white handle stamped with “BERG”)..
The best way to understand what it takes to install Berd spokes is to watch some of the process, so I made a video to show you. The most unique thing is how the spokes are attached to the hub, so I focus on that. There are two details not in the video I need to explain.
The first detail not shown is preparing the spoke holes. There can’t be any sharp edges that might cause the spokes to break. For this, Berd’s toolkit includes two drill bits for rounding and smoothing both sides of every spoke hole in both hubs. In the video you’ll see that the black anodizing is gone on all the holes from this process.
The second detail not shown is the process of attaching the spokes to the rim. It’s actually done just like with steel spokes with one difference. Berd spokes must be stretched a little in order to reach far enough to thread the nipples on.
The rectangular tool I mentioned above and shown in the photo, slips over the built-in flats on the ends of the spokes and by pulling up with the tool, you stretch the spokes so that you can start the nipples.
The other thing you can’t see is how long it took me to finish the wheels, which was more than twice as long as regular steel spoke wheels. Mostly that’s from the hub preparation and unique spoke-to-hub attachment. Also, Berd spokes stretch more than steel so the final tensioning took more time.
The part of the process that impressed me the most was being able to get Berd’s flexible polymer spokes to the same final tension as steel spokes. Just like with wire spokes, when you’re done with the wheel, the Berd spokes become so tight that you almost cut your hand when you squeeze them.
Enjoy the show!
Ride total: 9,466
Fantastic! I want these..
Jim,
It will be really interesting to have a review of these from an unbiased source such as yourself. I’m quite familiar with Sprectra/Dyneema fiber from my time in the archery business, where it is used extensively for bowstrings and cables on compound bows. As with spokes, it’s under high tension in these applications (though the load cycles are quite different). While it is indeed light weight and strong, it has one characteristic that could prove problematic; it’s sensitive to heat. Specifically, when exposed to temperatures that one might encounter in a closed vehicle on a hot, sunny day, it will “creep” (elongate permanently). There are many studies of this property available online. In a wheel, that could lead to substantial loss of spoke tension. It’s also my understanding that UHMWPE degrades under UV exposure, which could pose a long-term issue for spokes, which are expected to last a long time. I’m really curious to see what your experience is.
Thanks a lot for sharing these points, Brian. I appreciate knowing that heat and UV exposure can affect this material and I’ll watch for these things as we put these Berd spokes through the paces. Thanks so much for the education!
Jim
There should be no problem cleaning the UHMWPE spokes. I am a mechanical engineer at a food processing plant. We use strips and sheets of this polymer all over the place, especially on conveyors, to prevent conveyor belts from cutting in to the stainless steel frame and other components, and to protect against dirt falling off the raw vegetables prior to washing from abrading stainless moving parts. UHMW is nearly impervious to staining and resists abrasion far better than any metal.
It will cut though. I would not want to ride near any motor vehicle sporting “Mad Max” style knifes on their lug nuts! I would als worry about vandalism when locked up while I am in the quickie mart.
Thanks a lot for telling us about how UHMWPE outperforms metal in the food processing plant, Steve. That’s great to know. Regarding Mad Max lug nuts – quick release levers kind of resemble those!.
Thanks!!
Jim
If these ride as good as the Spinergy PBO spokes, the wheels should be very durable and comfortable. We have a pair of the Spinergy wheels on our tandem (24 spokes per wheel) and they have been bombproof over the past 3 years with a team weight of 375 lbs (riders and bike).
I didn’t even know Spinergy made a wheel with synthetic spokes, Mike, or I would have mentioned it. Thanks for telling us. Here’s a link for anyone who would like to see the spokes: http://www.spinergy.com/technology/
It’s quite a testament to their performance that 24-spoke wheels made with their PBO spokes can hold up to the watts that a tandem team crank out. Thank you for sharing!
Jim
When I investigated these the biggest potential issue I saw was creep, which would necessitate tensioning and truing the wheels on a regular basis. Also I suspect they have a lower modulus than steel? It will be interesting to see how they work for you.
Yes, I agree, Don and am interested to see how much retensioning they’re going to need over time.
Good point, thank you,
Jim
Very interesting, as others have said I would like to see an initial review and then sometime later after many miles another review. Of all the new stuff that has come out that I’ve frowned upon these look quite promising! And I hope they are. Nice work Mr Berd.
UHMWPE has been used for at least 20 years in total hip and total knee prostheses. It does not wear in these constructs.
That’s impressive, “M.” Thanks for letting us know.
Jim
Keep in mind that those are lubricated applications with very smooth surfaces rubbing against each other. That’s nothing like the environment they see in bike wheels.
I wonder how they will effect performance and pwoer transfer under hard acceleration (sprinting).
Yes, one nice thing about steel is that the hysteresis losses are very small. My guess is that this material is much greater. But then carbon parts have higher hysteresis as well and no one worries about that, so…
In a typical field sprint, torque on the wheel isn’t high because gearing is high. Torque would be much greater if sprinting on a steep climb, or even just riding up a steep climb.
These spokes will resist tension and will not resist compression. I don’t know the physics and engineering of spokes as they are used.
Steel spokes also need to stay in tension to contribute anything to the the integrity of the wheel.
Here’s a good explanation of how spoked bicycle wheels work, Del – the physics behind it, by John Forrester (famous bikeguy & engineer). Scroll for the diagram. https://johnforester.com/Articles/BicycleEng/Wheel.htm
Thanks for the comment,
Jim
This is why I roll my eyes whenever I see a review that say one type/brand of wheel rides smoother than another; it just shows the reviewer’s lack of understanding of how wheels are constructed and function. Tire deflection is orders of magnitude greater than rim deflection and even relatively small variations in pressure will result in far greater deflection than found at the rim. Casing construction and tread thickness result in greater deflection, too, so any review that doesn’t use the same tires/tubes and air pressure on every wheel tested is basically invalid. I would wager that in the vast majority of cases, it’s differences in the TIRES that reviewers are feeling.
Some wheels may damp high-frequency vibration better than others, which may create the perception that they’re somehow “softer”, but the truth is that there is no perceptible difference in rim deflection among wheels. Let’s also not discount the “placebo effect”, which we’re all prone to. If we THINK a wheel is going to feel a certain way, that’s what we’re likely to experience.
All that said, one area where wheels can exhibit significant differences is in lateral stiffness. This will affect how they feel in sprints, hard climbing and hard cornering, where there are significant lateral loads applied to the wheels. While I’m still somewhat skeptical of reviews claiming that one wheel is vastly superior in this regard to another – tires are a substantial factor in lateral stiffness, too – a least perceptible differences are within the realm of possibility.
Thank you for the reference, Jim. Studious work!
Spokes could be made lighter by using titanium ends. Have in mind nipples are made from heavy brass, aluminum alloy ones will be significantly lighter. Why not kevlar which is heat resistant?
At 4:52 to 4:54 in the video there is a spoke right at the hub flange on the far side of the hub near the top of the hub that appears to have a gap in the fiber, right in the middle of the spoke yarn, is that going to represent a weak area over time? I think I saw a few others like that too but that was the most clear picture of a gap.
I forgot to ask another question, once you smooth out a hub flange hole does that mean that if for some reason you decide to switch back to traditional steel spokes that the hub is now “damaged” and will no longer accept a steel spoke?
Sorry here I go again, but I’m researching this Berd Spoke so I’m stumbling across stuff. I can’t post a picture but if you go to this website: https://www.worldwidecyclery.com/blogs/worldwide-cyclery-blog/berd-spokes-wheel-review-the-worlds-lightest-bicycle-spoke-that-floats-on-water-video There is a picture of a white spoke by it self, at the loop there appears to be some cut fibers, that doesn’t look real secure to me. Which leads me to another question, knowing a little about Dyneema also known as UHMWPE braided fiber fishing line is that fiber is very susceptible to cutting and abrasion. I would be extremely concerned if the spokes rubbed up against something like a rock, am I justified in thinking that way?