Proud Sponsor of Monster Pro DH Series Season Champ Kallie Stewart
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MACRO
Making New Waves, Resurrecting Old Ones
Could this seemingly obvious technology potentially change the way mountain bikes are designed?
April 17, 2022
It was October 31st, 2019 and I was busy carving out a new business model for my MTB service shop in a pre-COVID world where many small retail bike shops had been on life support for years. "Different" was quite literally my biggest goal. Be unlike anything else in a significant way, because if I was going to venture into selling new bikes then duplicating the norm could lead to another slow death for yet another small retail shop. Locate rurally I thought. Very rural. Mountain bikers are chronic travelers, so a shop off the beaten path wouldn't be a problem if it made bikes more accessible from a dollars and cents standpoint. As I was breathing life into this vision, little did I know that those initial back and forth emails with Charlie at Berd on October 31st would eventually have the biggest impact on how I would shape a very key aspect of this new direction for a former service shop.
Having already ridden a variety of bike brands over the years (and then riding a few more out of due diligence) I opened a dealer account with Yeti Cycles [followed later by Ibis, Revel, Pivot, & most recently Mondraker]. Yeti had a reputation for a rear suspension platform that was firm at the sag point and pedaled particularly efficiently before opening up and getting active deeper in the stroke when things got rowdy to then smooth things out at speed. Speed is certainly requisite with Yeti, and having come from moto, I loved speed. Here in the Midwest we pedal almost constantly. No lung-busting climbs, but consequently nothing much to go down either. So because we pedal a lot (and eMTB's weren't en vogue yet) Yeti appealed.
The 2021 Yeti SB115 was a short travel 29er with a short wheelbase that excels at carving tight and twisty singletrack, hovering through Midwest rock gardens, and has just enough suspension to stick four foot drops-to-flat with plenty of confidence.
I could talk a lot about the high-end hubs and carbon rims I'd initially sent to Berd for them to lace up with their patented textile spokes, because those wheels rode great, spun up fast, and dampened vibration very well -- and it was a clear and noticeable difference vs. rigid spokes. But in October of 2020 I'd realized that it was high-time to let these professional engineers who had a specific rim spec'd for their novel spokes to go ahead and lace both of their products to my favorite hubs. I'll never forget that first ride on a set of Berd TR27's. And I don't just mean how light and fast they felt. There was certainly a mind-bending degree of wow-factor in that alone. But the overall ride quality was just different, and after all, my big goal with my shop was to be different.
Photo Credit: Nick_NoetheVisuals (IG)
When racing UCI sanctioned events, a wheel must withstand 40 joules of impact force to be deemed safe. Berd is dropping 116 joules of impact force onto these TR27's. The more capability that the rim has to compress without fracturing and/or pulling a nipple through the spoke bed, then the stronger the wheel will be.
The textile nature of the Berd spokes support this in several ways. It also took a lighter rim than what you'll find in most carbon wheelsets to maximize this bend-but-don't-break level of compliance. But in part, the wheel is stronger because the system as a whole is compliant.
So how exactly are they different? As stated, the ease of spin-up is inevitably going to be the first thing that you'll notice. Flat ground, mild climbs, techy climbs, steep climbs....it doesn't matter, they make it all easier. Techy climbs in particular stood out as I'm no stranger to stalling on exposed roots and square-edge rocks when climbing at slower speeds, so a wheel that can so easily spin back up to a reasonable speed in one good pedal stroke is good medicine on the occasional "carcass day" when my 210 pounds feels more like 250 pounds. But it isn't long before you begin to pinpoint the more subtle differences in the actual ride quality. The manner in which the textile nature of Berd spokes dampen vibration and reduce rider fatigue is, to me, their greatest attribute. Whether it's an hours-long ride, or even a shorter one with abundant small chatter and/or frequent rock gardens, you quickly come to appreciate the added comfort of superior vibration damping. But the light-bulb moment is when you realize how much that added comfort reduces fatigue at the same time you're pedaling against less rotational mass with a bit more energy in your tank. Either of those qualities in isolation are welcomed -- but in tandem they yield a sum much greater than their more subtle parts.
Suspension effect: The Midwest is hardtail and short travel 29er country, so the prospect of adding to a bike's limited suspension while simultaneously lightening it's rotational mass on our never-stop-pedaling terrain is enticing. That first set of wheels with Berd's original in-house TR27 rim arrived about the same time Yeti had just introduced their new ARC hardtail, so as I began mounting them to a new ARC, I thought "hey, why not toss a lightweight insert in the rear tire?" Yeti had touted a carbon layup for the ARC that was aimed at excellent vertical compliance for the rear of their new hardtail, but, I mean, it's still a hardtail, right? And the added rotational weight of the lightweight XC insert in just one tire had always been imperceivable under my 210 pounds.
The 2021 Yeti ARC with Berd TR27's and XC CushCore in the rear tire.
Up first was manualing the rear wheel into a common 6" city street curb near the shop. I'm confident my face went pale at impact as I'd thought for sure I had either pinch flatted or even slightly taco'd the rim. In short, it was an impact that quite literally wasn't an impact at all -- more of a hick-up instead. Something must have gave. But I quickly found a tire and rim that were both in tact and a mind that was racing and trying to process the confusion. Was it a fluke event that I'd never be able to reproduce, or something more? Again, then again, and yet again, I manualed into that section of concrete curb, daring to add a bit of speed each time. The results were the same each time. With my mind still racing, I hussled back into the shop curious to see if the rear tire still had the same 20 psi I'd started with. It did. At that point, I couldn't get that ARC into the service van fast enough to make my way over to some of our local trails that had some big roots and small drops. I had thought myself to be well past the hardtail phase in my own MTB life. Sure, I'd sell the heck out of them to new riders and to the hardtail enthusiast's, but I was a short travel 29er guy at this point. So what do you do when a hardtail rides like it has a 50mm travel rear shock, but still pedals as crisp and efficiently as any other hardtail?
Traction: As with anything that calms a wheel down -- be it perfectly dialed suspension or a little lower tire pressure -- traction is then improved. While this might be the most subtle benefit stemming from the compliance offered by a Berd spoke and rim combination, it's a notable one, and a nuanced one. Naunced because I believe the inter-relational dynamic between what a tire insert does and what a Berd spoke does could possibly result in what I referred to in this article's sub heading as something that could change the way some MTB's are designed. It's no mystery that tire insert's allow you to more safely run lower tire pressure to improve traction without as much risk of pinch flatting, burping, or even rolling the tire right off of the rim in high G turns. But with the Berd spoke's ability to fall out of tension so easily, there is also a bit of rebound effect when it returns to tension. If you can dampen some of that rebound effect then you've effectively added a little bit of very usable suspension capability to your bike. If you can do that while also significantly reducing rotational mass, then all the better, because in this case you're also reducing the ratio of unsprung mass to sprung mass (especially on these lighter bikes) and thereby improving your suspensions ability to react quickly to the terrain below it without disturbing the sprung mass (i.e. you) above it. With this reduced unsprung mass, the tire is able to track the ground in a more calm and resolved manner, which allows this wheel system to grab traction in corners in a particularly confidence inspiring way. Entry speed carried into corners can seemingly be pushed just a touch faster, and the added traction found through the middle of the turn then gives way to launching out of the turn with higher exit speeds.
Lateral Stiffness: Modules of elasticity.... stress divided by strain.... and other engineering terms of endearment are the kind of things most of us just don't want to try to wrap our minds around when we go about exchanging the complexities of life for the simplicity of rolling through nature on two wheels. But, inevitably, one of the first questions I often get from customers asking about a Berd wheel is, "won't they have more side flex in turns?" Given the limp nature of the unlaced spoke, it's certainly understandable that people might project that idea onto this system at first glance, but a wheel's lateral stiffness is almost entirely dictated by the strength of the spokes in their pulled tension, the specified amount of tension they are set at, and by the bracing angle between the hub flange and the rim's nipple bed -- followed then by the width and lateral rigidity of the rim itself.
A wider hub with more space between the spoke flanges, and/or a larger diameter spoke flange, increases the bracing angle and thereby increases potential to make the wheel laterally stiffer. And under tension, Berd spokes have been tested to be up to 4x stronger than rigid spokes. Granted, Berd spokes need to undergo a couple of overnight rest and re-tensioning periods during the wheel building process in order to effectively achieve a strength under tension that is greater than steel spokes, but the product as delivered to the customer has been through that process, and (at most) the same basic spot true and minor re-tensioning procedure that is typically part of an annual Spring tune-up for any type of common bike wheel is all the attention you may ever need to give to these wheels to keep them on par with the lateral stiffness of a metal-spoked wheel. If you're a bigger and/or very aggressive rider, I always recommend out of due diligence to check tension by no later than 500 miles.
Conclusion [updated]: If there could only be one central starting point when I build my own personal bikes, then right now it's gotta be a Berd wheelset -- and even more so now that Berd has enlisted the minds at We Are One to help them design a rim from the ground up around the specific qualities of the Berd spoke -- giving birth to the Berd Hawk series rims. As I've began telling my customers when they are in that stage of deep contemplation to find the right direction on their next bike, "just buy Berd wheelset and build a bike around that." No joke. If you feel like you couldn't go back to riding without a dropper post, then chances are you'll feel the same way after adapting to a Berd wheel system. I didn't see this coming back on October 31st, 2019, but I can't think of anything that I've been a part of in the MTB industry since starting as a service-only shop back in 2015 that has brought me more satisfaction than seeing this seemingly obvious technology and this small company grow into what it is quickly becoming.
Happy Trails,
Clint @ Boone Cycles