More distance, less time.
When describing its tubeless-ready 303 Firecrest Carbon Disc Brake Road Wheel, Zipp rather drily notes that, when you're challenging the ever-expanding terrain available courtesy of the new generation of gravel grinders, the wheel will "go the distance. It'll just take less time." It's based on the same 303 depth that we first saw storm to multi-surface success under Spartacus at Flanders in 2010, but the latest 303 platform combines strength, stability, and the aerodynamic features the brand is known for in a body that, if Cancellara had it those seven years ago, may well have pushed the final gap out to two minutes or more.
The "takes less time" part of Zipp's claim is obvious: the brand was one of the early adapters of the bullet-shaped rim cross section that's swept the industry in recent years, and it's of course synonymous with Aerodynamic Boundary Layer Control (ABLC) dimpling. When compared to smooth-sided rims, Zipp credits those dimples with reducing drag across all yaw angles; however, the largest gains occur between 10 and 20 degrees, a range that Zipp claims encompasses 50% of the time we spend on the bike. By combining the gains of ABLC with the natural tendency for 45mm rims to want to hold speed in the low- to high-20s, Zipp maximizes aerodynamics.
Zipp also credits ABLC with stabilizing the wheel in crosswinds, but the new generation's titanic internal width of 21mm may have a far more significant impact, stability-wise. That width lets you run 28mm tires with impunity—in fact, Zipp recommends that size because it brings the tire's side walls neatly in line with the rim's outer face, reducing the air-tripping transitional ridge caused by narrower rims. A wider rim and plumper tire (Indulge in 28s. You won't regret it.) allow for higher air volume and a lower PSI, so when the 303 Firecrest Tubeless is paired with a big tire, it rolls more smoothly through obstacles, deforming around gravel and lumps rather than bouncing over them. That reduces rolling resistance and actually makes the tire faster—a difficult lesson for many of the 23mm/120PSI hold outs in the Competitive office to wrap their heads around. Riding is believing, though, and we're all believers now.
Rim width isn't the only speed gain enjoyed by the Firecrest Tubeless Disc platform. Since disc brakes require no rim brake track, the ABLC dimples also extend to within millimeters of the rim bead, so the little dimples begin their work of managing airflow much sooner. The cumulative gains of all of the above feel, well, zippy. We don't have laboratory numbers to quantify this, but we've seen some industry publications run tests that do support our assertions. And anyway, the real testing ground for a wheel like this is across limestone gravel, hardpack singletrack, and—yes—the Flemish stones.
- A gravel or 'cross race wheel that goes the distance in less time
- Deep, dimpled carbon rim reduces drag at common yaw angles
- Bullet-shaped rim cross section stabilizes in crosswinds
- Generous width reduces rolling resistance with large tires
- Disc brakes provide precisely modulated, confident stopping
- VCLC laminate layer adds vibration damping to the rim