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Designing the new Zipp 303 Firecrest

Words by William Tracy with images from Zipp

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For more than three decades, Zipp has been at the forefront of manufacturing carbon wheels, turning out some of the lightest and most aerodynamic models and helping make carbon rims a ubiquitous sight from the pro peloton to the local group ride.

The brand has had many successful models. But the 303, for the first years of its existence, sat in a bit of an awkward position in the brand’s lineup—sandwiched between the 202, a lightweight climber’s wheel, and the 404, a deep-section aero wheel. Like the middle bun in a Big Mac, it seemed a little lost between the two, never quite sure who it was for.

The 303 soon found its way, though. A new rim shape helped Fabian Cancellara win the Tour of Flanders and Paris–Roubaix in 2010. Over time, it became more useful for other disciplines including cyclocross—and more recently it has perfectly suited the demands of gravel cycling. It is now Zipp’s best-selling product and features the most versions of any Zipp wheel. When you have a product of this level of importance, you don’t want to make any changes lightly.

David Morse, an advanced development engineer who has been at Zipp for 12 years, says development for the latest iteration of the 303 Firecrest started about two years ago. It was a complete overhaul. “The project name was Clean Sheet,” he says. “We started all in one room and literally threw out all the assumptions we had been carrying forward for the past 15 years of what a wheel should be and what it should do.” Morse remembers it being an uncomfortable process because there was zero direction. Everyone at Zipp was trying to figure out what really mattered.

In the end, the “Clean Sheet” method produced quite an overhauled wheelset. The set has become 300 grams lighter, now weighing 1,355 grams. It’s also faster, getting a 5mm shallower rim depth of 40mm. Plus, it accommodates wider tires with its 25mm internal rim width, making it more versatile. And while wheels have been getting lighter and faster over the years they’ve also been steadily marching up in price. The new 303 Firecrest is a refreshing departure from this trend, with a slashed price tag of $1,900, which is $600 cheaper than before. But getting to this point took a lot of dedicated testing and development.

Zipp wheel product manager Bastien Donze says that early on the development team realized that it might take more than aerodynamics, something which Zipp has been at the forefront of for decades, to make a fast wheel. When you look beyond aerodynamics, “you start to open up your mind and that opens up a lot of potential for new avenues,” he says.

From developing the MOTO, a mountain bike wheel, Zipp engineers gleaned a new perspective on wheel design. They also noticed that the way gravel cyclists talk about their wheel-and-tire setup is much closer to how a mountain biker talks than a roadie. That really opened up their blinders to things in addition to aerodynamics to focus on, says Morse.

One of the most significant changes to the 303 Firecrest is its hookless rim. “The hookless rim design was a means to an end,” says Morse. Though not common on road wheels yet, a hookless rim, which does away with a rim hook that secures a tire and is compatible with tubeless tires only, soon became the obvious choice through testing. When Zipp engineers verified that they didn’t need to go above 73 psi to deliver the fastest wheel-tire combo, the floodgates opened up, says Morse.

The hookless rim enabled Zipp’s engineers to take a more holistic approach to design, implementing something called TSE (Total System Efficiency) technology, which looks at four key areas: aerodynamics, gravity (weight), rolling resistance and vibration losses.

The first two of those factors are well known to riders. Zipp managed to reduce drag by making a smoother transition between the tire and the rim. And the weight savings—300 grams, while increasing overall strength—are truly impressive. “More than any other product since I’ve been at Zipp over the past 12 years, we put more resources into dropping weight than we ever have,” says Morse.

The other two factors in TSE are not on the radar of many cyclists. Rolling resistance has been decreased by widening the tire bed to 25mm, which makes for a wider and shorter tire contact patch. The result is less tire deflection and less energy loss. And Zipp has been able to reduce vibration losses through wider tires and lower air pressure, which together act like a sort of suspension.

While awareness of vibration losses—energy lost to small bumps in the road—isn’t necessarily new, Zipp has finally been able to quantify and reduce this phenomenon through its new RollingRoad Testing Protocol—essentially, a beefed-up treadmill with sensors to which they can affix different textures and obstacles. When compared to the power meter data it takes a cyclist to maintain a certain speed, the tool has allowed Zipp to isolate the effects of vibration on the efficiency of the whole rider. “It’s been really eye-opening to see how much power can be lost to this phenomenon,” Morse says. “It’s kind of like discovering a new form of matter. We had aero, and we had gravity, and that’s what the cycling industry was paying attention to for the past 50 years. Now we have vibration loss—so it’s been pretty awesome to be on the forefront of this.”

When it comes to developing new wheel concepts, Zipp relies mainly on its internal team but it also picks up good ideas from its sponsored athletes. Designing bicycle wheels makes testing more accessible. “We’re really lucky that the product can be used directly by the engineering team,” Morse says. “If we’re designing a race car, there’s only so many people that can handle a race car at racing speeds.” But at Zipp, at least half of the engineering crew rides regularly and can provide in-depth feedback and apply their engineering understanding to make refinements.

Those refinements find their way into new prototypes. Morse estimates a refinement to an existing wheel might require just a couple dozen or so prototypes, but that a brand-new wheel may go through up to 1,000 prototypes before entering production—though he says the number has come down over the years.

Beyond all the new technology and design that goes into the latest 303 Firecrest wheels, most people are probably going to notice the new logo first. “I don’t think I’ve had more passionate discussions at Zipp than we’ve had about the graphics development,” Donze says. “That was a long and strenuous journey.”

The graphics update, like many others before it at other brands, left some divided opinions internally. But, overall, Donze says it feels like an appropriate update now that the brand is focusing beyond just aerodynamics and looking at overall wheel efficiency. It’s a new logo fitting for a new era of Zipp wheel design.

From issue 95. Buy it here.