Tech Feature: Felt Bicycles’ 2011 line

Felt refines its road line with a new carbon bladder process that led to lighter and stiffer frames.

Felt Bicycles 2011 road bikes
Felt Bicycles road product manager Dave Koesel shows off the new DA time trial and triathlon flagship.

Building a better mousetrap sometimes just requires better tools.

In the case of Felt Bicycles, revisions to the 2011 bike line didn’t start with simply throwing new materials and more exotic shapes into the mix. The process began with developing better tools. The end result is lighter, stiffer frames and a wider array of potential frame shapes.

During a media event at company headquarters in Irvine, California, Felt showed three new flagship race bikes. Felt’s new DA time trial and triathlon bike, the new F-series road frames, and the Edict cross-country race frame are all products of new construction methods and a constant quest for improvement. Additionally, product managers made a point of drawing attention to more affordable bikes that will make elite performance available at a more reasonable price.

Recent beginnings, rapid growth

Felt Bicycles is a small company, with a roster tipping over 50 employees for the first time this year. Eight of those employees are engineers. It’s also a relatively new company, founded just over ten years ago. But the company’s size and youth hasn’t been a deterrence for founder Jim Felt and president Bill Duehring. These two, plus a third business partner in Europe, have worked harmoniously from day one to continue their brand’s ascendance in the world cycling market. As Duehring said, Felt’s mission statement is not to be the biggest, but to be the best. “We are a product-driven company, and as long as Jim and I are alive, we will be a product driven company,” said Duehring.

Jim Felt himself has an extensive background in racing. His experience spans the gamut from cars to motorcycles to bicycles. And while Felt Bicycle’s major product developments are spurred by competitive goals at the high end, technology often trickles down throughout the entire range of Felt bikes. The company is well known in the USA among elite road and triathlon racers, but its products span a full spectrum of mountain bikes, urban bikes, cruisers, and BMX bikes, and they’re popular in Europe and around the world.

One of Felt’s major claims to fame is not just the pursuit of expensive, exotic bikes at the high end, but making premium performance affordable to average riders. For example, Felt product managers built several Shimano Di2 bikes into the 2011 range with prices just over $6000. It sounds like a lot, but considering that a Di2 drivetrain alone retails for $4000, finding a complete Di2 bike for less than $9000 is a rarity. On the mountain bike side, Felt has a complete 29er hardtail (the Nine Trail) on offer in 2011 for just over $600. High-end performance combined with good values across the line are Felt Bicycle’s hallmarks.

Felt Bicycles 2011 road bikes
These two-halved polyurethane internal molds are pressurized with the nylon air bladder and keep the internal structure of the frames consistent.

After early leaks, a closer look

The racing world has already stolen peeks at Felt’s flagship frame platforms.

The new DA time trial and triathlon bike unveiled at the Tour of California under the Garmin-Transitions team sports a slew of sweet design features. The aero tubes are exceedingly slender, as is the new, narrower Bayonet fork and head tube. A wide fork and rear stays help keep airflow smooth through and around the wheels. This open, smooth design also keeps the bike “wheel neutral,” so it performs well no matter what wheels are mounted in the frame. Little flares or “trips” on the trailing edges of the seat tube and seat post trick the wind into flowing smoothly off the rear of the bike.

At the start of the Tour de France in Rotterdam, Jim Felt himself showed off an early version of the 2011 F1 road frame. According to Felt, it’s lighter (by about 100 grams) and stiffer (by about 35 percent) than its predecessor. The entire F-series of road frames incorporates the new tube shapes, tapered head tube, and oversized bottom bracket, but particular attention to materials and assembly bring the top-end F1 into the range of seriously competitive road frames.

And way back in April at the Sea Otter Classic, Felt gave us an early look at the Edict cross country bike. It’s a short travel (100mm) full suspension bike with a pivotless, all carbon rear triangle and rocker link activated shock. The design is reminiscent of a Trek Top Fuel circa 2006, but the pivots, hardware, frame geometry, and design elements are all dialed up to the demands of modern World Cup athletes.

Improving the process to improve performance

Neither of these flagship race bikes would have been possible without new construction methods. Felt director of research and development Jeff Soucek was remarkably candid about the limitations of carbon molding and how he and his team of engineers have worked to overcome them. He described the different material properties of 30-, 40-, and 60-ton carbon fiber (basically, they’re progressively stiffer in one orientation) and their ply orientations in terms of stiffness and strength (carbon plies or layers are strong in only one direction and have to be layered in multiple orientations to achieve suitable strength).

The “recipe” for a given frame in a given size is called the layup schedule. Soucek showed a layup schedule for one particular frame that ran into the tens of pages. It’s essentially a spreadsheet that lists in explicit detail the exact type, size, shape, and placement of each layer of carbon as it goes into a mold. Frames of different sizes require different cuts and placement of carbon plies, so there are different layup schedules for each size of each frame.

Felt blends materials depending on the weight and price targets for a given bike. Lighter materials also tend to be more expensive. At the top end, Felt’s Ultra Hybrid Carbon (UHC) Ultimate+Nano is their lightest, strongest blend. The proprietary resin (Nano Tech) that’s pre-impregnated in this material creates a stronger bond between fibers and adds impact resistance.

External heat and pressure cures carbon fabric that’s cut to shape and layered into molds. But pressure has to be applied inside the frame as well. In Felt’s original process, internal tube-shaped nylon bags were inflated to provide that internal pressure.

“What happens is, on the old process you had the nylon bladder that was inside the frame, it inflates and pushes the carbon out,” said Soucek. “The bladder material is not very flexible so you can’t expect it to expand and fill up every little corner of the frame. What you have do is that in areas like that, you have to add some little foam corners or little reinforcement areas so the bladder flows nice and smooth around the frame and makes a good compact structure,” Soucek explained. “Well, all that’s good for strength but it adds a little bit of weight to the frame.”

Felt Bicycles 2011 road bikes
As Soucek explained, 30-ton carbon on the left isn't as stiff as the 60-ton on the right. The 1K woven fabric on the top right is about two-thirds the weight of the 3K on left. Felt's top end bikes are a careful blend of the lighter, more expensive materials shown.

In order to create more complex tube shapes with really clean interior structure and no superfluous material, Felt engineers came up with a new interior molding method. “What we’ve started doing is the process that we call our Inside Out technology. We’re using it not only in the F1 frame, but we’re using it in the mountain bike frames, we’re using it in a wide range of the products that we do,” said Soucek.

The new method employs hollow, flexible polyurethane internal molds to precisely and cleanly shape frame sub-sections. The same nylon air bladders are still inserted and pressurized inside these new internal molds, but now the molds dictate more accurately the internal shape, forcing the carbon and resin more cleanly into form. “The difference is now the bladder pushes against the urethane, and the urethane pushes against the carbon,” described Soucek. “So any of those areas that had tight little corners or intricate little shapes where we used to have to use foam or filler, it no longer has to be there.”

In addition to the InsideOut internal molding, Felt is employing a new method for manufacturing and joining different sections of the frame. It’s called Dynamic Monocoque Construction. Large sub-sections of the frame are molded separately, and then co-molded together with additional plies of material in a separate assembly step. It’s a complex process reserved for the high-end F-series frames, but it results in the lightest frames possible.

With these tools, Felt engineers have freedom to not only mold more subtle shapes, but use less material to do so. By the looks of it, every carbon frame in the 2011 Felt line reaps the benefits.

Highlights of the 2011 Felt road bike line

F-Series road bikes

Felt’s top road racing frame, the F1, gets a complete redesign for 2011. As a result of design and materials, the 2011 F1 is 100 grams lighter and 35 percent stiffer than the current F1. The F-series frames all share the same shapes and major design features, but lighter materials and more complex assembly at the F1 level keep it more expensive and lighter than the other F-series frames.

The top-end F1 is spec’d with a complete Shimano Di2 group, Mavic Cosmic Carbone Ultimate wheels, and 3T components for $12,500. The F5, with Shimano 105 and Mavic CXP-22 wheels will cost $2000. Both frames are the same in terms of design elements, but the F1 uses different materials and construction.

Major frame design elements in the F-series include a BB30 bottom bracket, tapered head tube with 1.5-inch lower bearing, and cable routing to accommodate either internal Di2 wires or retrofitted cable stops for external mechanical cables. There’s a Di2 battery mount under the left chainstay. In terms of tube shapes, the new F-series has more square-shaped ends and rounded midsections.

Felt Bicycles 2011 road bikes
From this cutaway of the lower bottom bracket structure, small individual squares of carbon can be seen layering over the top of each other. The glue joint with the rest of the frame tube is also visible.

DA time trial/triathlon bike

The exotic new DA time trial bike benefits from  surface area increased (by 25 percent) to create smoother airfoils. The head tube is narrower (35mm instead of 42mm) and hides a pair of custom ¾-inch headset bearings. Felt’s Bayonet 3 fork functions the same as the current Bayonet 2, but it’s narrower up top and wider in the blades to facilitate smooth airflow. There’s a new, mini v-brake style rear brake under the chainstays. And finally, the seat tube gets a true airfoil shape with flares or “trips” at the trailing edge to keep airflow smooth onto the back wheel.

Despite all the new engineering and what seems like more frame material, Felt’s new processes kept the weight to only about 2 percent more than the current DA.

While the DA is at the top of the range, aero bikes like the B-series bring time trial and triathlon performance to more affordable levels. The B2 is equipped with Di2 for just $6500, and the Ultegra/FSA B16 is just $2000. Pricing and spec on the flagship 2011 DA time trial bike are yet to be determined.

And for details on the 2011 Felt mountain bike line, including the new Edict race bike and the Virtue trail bike line, check out in the coming days.