Carbon Optimized Design
From the outset, in designing our wheels, we asked a simple question: what is the best way to apply carbon to the wheel building process? Should we follow what has come before, and simply use carbon to emulate structures (extruded rims, forged spokes, threaded nipples) that have been optimized to be made of metal? Or should we go a different way and develop new techniques to get the most out of carbon fiber's superior properties?
The answer is obvious, no? And to be successful in that, we had to do two key things that lead us to creating several new, patent pending processes and designs for building wheels with carbon:
- Build our carbon rims in a way that facilitates consistency of production and performance of final product rather than striving to replicate extruded metal rims.
- Use carbon spokes, built and connected to both hub and rim in a way that maximizes the benefit of carbon rather than using or simulating metal spokes.
Mad Fiber rims are built from three distinct pieces (the two sidewalls and the tire seat). As opposed to using a manufacturing system of bladders and molds to emulate an extruded metal rim, this enables exceptional control of the carbon manufacturing process, minimizing voids and eliminating the use of excess resin, resulting in increased strength and decreased weight.
There's an awful lot of talk in the market about making (and reinforcing) spoke holes in carbon rims. We've seen carbon rims drilled just like traditional aluminum rims. We've seen carbon rims with the holes molded into the rim (with reinforcing fibers placed around the openings). And we've seen threaded inserts riveted into drilled holes to at once reinforce them and allow the use of externally threaded spoke nipples.
What's it all mean? To us, it's clear: using traditional spokes and nipples with carbon rims is an imperfect proposition. Creating a hole in the rim weakens the rim right at the point where the spokes and nipples apply a stress concentration. Hence the myriad reinforcing techniques and subsequent debate about which is better. So we went a different way.
We bond wide carbon spokes to both the rim walls and the flanges. This eliminates the issue of spoke hole drilling/reinforcing, and it spreads wheel loads over a broad area, increasing strength and aerodynamic benefit while decreasing weight.
So, no threads, right? Great. But that leaves the question of how to tension the wheel. Because anyone who has ever ridden a wheel that works with the spokes in compression understands: tensioned wheels feel better and deliver more strength for a given weight.
To understand the solution, you've got to think back to your high school trigonometry class. Imagine a line drawn from the rim straight to the center of the hub body. Now imagine a line drawn from the rim center to the hub flange. It's a longer distance to the hub flange than it is to the hub center, right?
The spokes are bonded to the rim walls and hub flanges before the flanges are fixed to the hub body. This means that their un-tensioned lengths correspond to the distance from the rim to the hub center. Then all of the parts are placed in a fixture that allows us to precisely move the flanges to the outside of the hub body and bond them in place, simultaneously tensioning the wheel as the spokes are pulled into the position that requires them to cover a longer distance.
By considering all of the demands on the spokes and wheels: requisite tension to produce the desired strength and ride feel; spoke length and flange spacing dimensions to produce this tension; and optimal flange spacing for aerodynamics, we were able to create a wheel with the desired characteristics and do it in a way that comes out of the jig perfectly straight - and never goes out of true.
That the same wheel approaches or exceed the strength, aerodynamic and weight standards set by the industry's best offerings in each category? That's the result of carbon optimized design. The difference between using carbon to emulate parts originally made of metal and instead, designing parts from the beginning to take advantage of carbon's superior properties.
NEXT: Built To Last
