We’ve heard enough about wheels and standards relating to them in recent times that it could send us to the looney bin. It really was the main thing to note at Sea Otter—every man and his dog are either starting a wheel brand or pushing “new” wheels to the audience. But what if there was a different take on how to make wheels stiffer and stronger? Is it possible that many of these wheel makers are, more or less, just following each other around in circles (no pun intended) on this whole Boost 110/148 thing? One man, American Classic's Bill Shook, thinks so.
It was with a similar borderline insanity that I stumbled over—not from drinking, but rather, fatigue, thanks to a busy week and having dealt with wheels enough to last anyone a lifetime—to the American Classic booth. However, when I arrived I was greeted by Bill, who shortly after greeting me went on to share his concept behind what actually makes a strong wheel, and that from his research, everyone is using Boost to do nothing more than generating a wider flanged, but still problematic system.
Bill’s research led him to go with a more symmetrical front and rear wheel. He moved the rear wheel's disc side out 6mm, which resulted in the center of the hub moving 3mm, creating a rear wheel with the rim sitting almost symmetric between the hub flanges. On the front Bill designed a new axle to work with the Boost spacing, which resulted in a total of 10mm being added to the non-disc side of the hub, also creating an almost symmetric spacing.
So where does the idea for all of this come from and how is a slightly narrower flanged, symmetric wheel actually stronger than a wider one that creates a larger bracing angle for the spokes? The theory around conventional Boost wheels makes a lot of sense to many, but Bill has a fairly insightful point to add. He notes that when the stats for the Boost width flanged wheels are made, it’s in relation to a static wheel, and from this perspective, he agrees that they are indeed a stronger wheel. The problem is that we ride our bikes (hopefully) and that movement on a wheel puts varying forces into the wheel at different points, so why are we looking at stats from a static test?
When riding a set of wheels different loads are going through the spokes. Bill notes that when rolling the spokes are loaded from the top and at the bottom, the load is relieved. As a result, the tension in the spokes is constantly moving up and down as the wheel rolls. A non-symmetrical triangulation (dish) in the wheel generates a pull from side to side, a result of the tension moving unequally because of a lack of symmetry. With that said, if a wheel is going to be used (as in, if we were to look at the numbers for a dynamic test), Bill has found that a stiffer wheel can be created from a symmetrical setup, with the axial tension changing the same amount on each side and the rim remaining in the center. If the non-drive side were pulled out, creating an unequal dish, then as the tension in the spokes goes up and down the rim will be pulled over, releasing tension every time. This is one of the causes of wheels going out of true—a symmetric wheel will stay true better because it is not moving the rim around as it is ridden.
The flipside to this is that the flange spacing can be too narrow, creating a wheel that is not stiff enough and Bill is the first to admit this, but with the current measurements, American Classic believe that going for symmetry over the wider bracing angle afforded with boost, is of more benefit to riders. Bill says that Boost is a good thing, thanks to the extra space allowing the spacing to be shifted and worked within, while still granting enough triangulation in the wheel.
We also asked Bill why not utilize an asymmetric rim in an effort to achieve the same thing. He noted that while it is possible to gain greater spoke symmetry with an asymmetric rim, it's not the best way to do so when considering function and wheel life. Asymmetric wheels need to be very off center in order to achieve the same amount of symmetry and this creates a twisting motion in the rim itself. That twisting will cause fatigue to the rim quicker than a rim without it.
At the end of the day, everyone is trying to make a stronger wheel with Boost and Bill Shook’s alternate theory is a compelling one. Yes, Boost 148 affords a better spoke bracing angle but the holy grail of wheel building has always been evenly tensioned spokes. It's a bit of a wonder why our industry seemed to put all of the cards on pushing the hub flanges out and improving the bracing angle when they could have done as Bill seems to have here and created a wheel with less dish and more evenly tensioned spokes.
Of course, absent a dynamic test that compares a Boost 110/148 wheelset with an identical wheelset (in terms of materials and lacing patterns) featuring American Classic's approach, it's impossible to say exactly where the truth lies at this point. The likes of Yoann Barelli and Cècile Ravanel, however, are putting these American Classic wheels to the test on the Enduro World Series this year… If we’re looking for further proof of the concept, perhaps we should start by keeping and eye on how those riders fare on American Classic's wheels.