Consumers May Be Surprised At How Light, Fast, Snappy, and Tough A Bike They’ve Barely Heard Of Can Be
Written by Lennard Zinn of Velonews
If I had a dollar for every time I’ve been told, “We’re a small company, and the only way we can compete with the big companies is to make a better product,” I’d be a very rich man. Given the engineering budgets of companies like Trek, Specialized, Giant, and Cannondale, it’s hard to make a bike better than they make. But Felt Bicycles is a small company that surpasses them in some areas.
Just the fact that you most likely hear very little about Felt, especially now that its bikes are no longer being ridden by UCI WorldTour teams, may indicate that it’s not a marketing-driven company. Rather, it is a product-driven company, and has been ever since Jim Felt started making custom aluminum bikes with his name on them decades ago. Felt employs a small team of talented engineers, and the company and its product line are too small for them to be dedicated to single categories. Instead, ideas that work on road bikes rapidly cross-pollinate to mountain, cyclocross, and track bikes, and vice versa.
Some of these ideas can make a big difference. Here are a number of innovative details of Felt bikes that could easily escape notice, yet I believe they are rare enough and important enough to make Felt bikes stand out as superior in these areas.
You may think that how a seatpost is clamped to the bike is a yawner. However, with a material like carbon that only works well in tension and not in compression, it’s a significant issue. A seat binder generally works by compressing both the top of the seat tube and the seatpost. But to optimize stiffness of both the frame and the post, both are built with stiff fibers that can’t tolerate being pinched; the fibers will crack if deflected very far over a short distance by the seat binder clamp.
Felt’s solution for clamping aero seatposts is unique and game-changing, and its solution for clamping round posts puts reliability above weight and style considerations.
Because it isn’t round, an aero seatpost cannot be clamped inside an aero-shaped seat tube with a constricting band clamp. Instead, the clamp has to push on the trailing or leading edge of the post to wedge the opposite edge tightly against the inner wall of the seat tube or clamp. Felt uses a completely different seatpost-clamping system that also cuts the weight and the vertical rigidity of its aero posts. (And its aero posts can be huge, from the UCI-legal (3-to-1 depth-to-width ratio) aero seatposts on its AR-series aero road bikes and DA-series time trial bikes, to the extremely huge UCI-illegal (more like 8-to-1) aero seatposts on its IA triathlon bikes.)
Instead of clamping around the post or wedging it from the front or back, Felt clamps each wall of the aero seatpost against each inner wall of the seat tube by means of a vertical slot running down each side of the post. On each side, a bolt extending out of a thickened area at the top edge of the seat tube passes through the seatpost slot and threads into a separate aluminum plate conforming to the inner shape of the seatpost wall. Tightening each bolt simply clamps each wall of the seatpost flat between each aluminum plate and the wall of the seat tube.
To illustrate the concept, consider driving over a flat carbon-fiber sheet on a smooth concrete floor versus driving over a carbon seatpost. Obviously, the car tire will not crush the sheet of carbon, because there is no air space to compress it into, but it will crush both a round and an aero carbon seatpost.
The benefit to Felt’s clamping system is not just reliable clamping; it is also reduced weight, increased comfort, and increased frame durability. Since it does not have to withstand crushing forces to hold it in place, the seatpost walls can be very thin (you can easily flex the side walls of Felt AR, DA, and IA seatposts with your fingers) and hence lightweight. This also provides a slight amount of vertical compliance to a seatpost shape with which comfort is hard to come by. Finally, it prevents tearing the frame apart by tightening the seatpost, which is what wedge clamps are doing.
Clamps that wedge the seatpost from the back are effectively trying to tear the back of the seat tube off (so it has to be overbuilt and heavier to withstand it), and systems that wedge the seatpost from the front are effectively working to tear the top tube away from the seat tube. This may be part of the reason that you sometimes see bikes of pro riders tear apart in a crash at the wedge clamp inside the top tube that pushes against the seatpost; the rider standing out of the saddle is twisting at this area stuffed with carbon in a much less effective layup than throughout the rest of the frame.
Beyond a great clamping system, Felt builds a little suspension into its big “Vibration Reducing Aero” seatposts by encasing 3T’s “Difflock Comfort Module” saddle clamp in them. This 3T system fits into the large cross-hole in the top of the post. It surrounds the rail-clamping core with an elastic polymer allowing the cylindrical clamping module to twist and return when the rider hits a bump. The clamp also will accept all of the different available shapes of saddle rails without interchanging clamp parts. Finally, the seatposts are flip-position with different offsets available.
Even Felt’s round seatpost-clamping systems are different from the run of the mill. In its carbon F-series road racing, Z-series endurance road, and ZW-series women’s road bikes, Felt doesn’t chop weight by using a thin, single-bolt clamp. Instead, F, Z, and ZW frames all have taller two-bolt aluminum seat binder clamps, despite the battle to get frames below target weights, like the magical sub-700-gram weight. The 700-gram Felt F FRD frame does have a pair of titanium bolts threading into a scandium nut bar in the tall clamp; do does the F1. And rather than using a single slot, Felt has two slots on opposite sides of the seat tube, to reduce the amount that any individual fiber is forced to bend.
Carbon frames and forks used to have a woven top layer for aesthetic purposes that provided little additional strength or stiffness, while adding weight. Perhaps you assumed, as I did, that the checkerboard-weave top layer of Felt’s top frames is like this, but it isn’t. Instead, that layer of TeXtreme fabric actually saves weight and adds toughness to Felt frames, but it costs around 10 times as much as the unidirectional fabric it replaces.
TeXtreme Spread Tow Fabric offers the strength and toughness of two layers of unidirectional carbon in a single layer of the same weight as one of those unidirectional layers. Unidirectional carbon layers cannot stand alone for the same reason that a bulletproof vest made out of fibers all running the same direction could not stop a bullet; an impact can split the fibers if crossing ones are not there to hold them together.
Since the broad packets (“tows”) of TeXtreme fibers cross at 90 degrees, forming the checkerboard pattern, they provide the toughness of two crossing layers of unidirectional fabric with a single layer. Furthermore, the weaving allows thinner fibers to be used in the fabric without it being too delicate for human hands to wrap around a frame shape.
For added security, Felt uses a TeXtreme layer on the inside of the frame as well — the first layer workers put down. This can prevent “mystery” carbon frame failures by preventing fibers from imploding inward on impact. If a carbon frame takes an impact, it is often difficult to tell that there has been damage on the surface. But the sharp application of force can break internal fiber layers, which can splay out inside of the frame. Cracks can then propagate from there, and a rider’s frame may suddenly fail while JRA (“just riding along”), but the failure was actually due to a prior crash. Felt’s layer of woven TeXtreme inside can prevent severed unidirectional fabric fibers from splaying into the interior of the frame tube on impact, and can therefore stop the propagation of a crack.
TeXtreme fabric is made in Sweden, and due to laws intended to prevent strategic materials from falling into the hands of the Chinese military, Felt had to import it to the United States, have it impregnated with resin certified as being non-weapons-grade, and then send the pre-preg fabric, refrigerated, to China for use in its frames. You can imagine the added costs. Once Felt bought enough of it, TeXtreme went through a certification process with the U.S. government so that it sends the fabric to China directly, and it is pre-pregged there; this cost savings has made it possible for Felt to now use TeXtreme in a second model from the top in each frame series
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