We typically sell Zipp wheels as individual hoops, letting you mix and match rim depths for whatever discipline you're targeting; however, with the 404 Firecrest Carbon Clincher Road Wheelset, we've taken the liberty of packaging them as the more conservative cyclists would have them: a complementary pair of mirrored rim depths. The latest generation of 404 Firecrests feature the same proven all-purpose depth with a new pattern of Advanced Boundary Layer Control (ABLC) dimpling and a reinforced rim that further improves reliability compared to its cobblestone-proven predecessor.
As with any deep Zipp wheel, the 404 Firecrest's side-wall bulge and ABLC texturing are its signature features, both of which contribute to improved stability at the kind of yaw angles you'll actually experience on the road, not while cloistered in a wind tunnel. While these two features tend to steal the headlines, Zipp's Visco-Elastic Constrained Layer Control (VCLC) and Carbon Bridge technologies may be even more impressive despite being less evident from a visual standpoint.
VCLC is similar to a construction model that we're seeing more and more in high-end frame manufacturing, especially among the venerable Italian names. To unpack Zipp's initialism, VCLC involves constraining a visco-elastic layer between the wheels' carbon and resin layers in order to increase the structure's ability to absorb and control road noise. As mentioned above, we're used to seeing this in racing frames, but Zipp may be the only manufacturer to bring it to wheels.
The Carbon Bridge design incorporates Kevlar threads in the carbon layup to take advantage of Kevlar's 350% greater resistance to impact. The benefits throughout the wheel are obvious, but higher durability is especially welcome at the tire mounting surface, which is often the first area to take a hit when tires flat, and Zipp claims that the 404's durability under duress jumps by just over 40%.
The rims are anchored by their final new feature, Zipp's new 77 and 177 hubs in the front and back, respectively. The new hub model features a flange and spoke lace design meant to decrease the torsional and lateral flex produced by hard accelerations, sprinting, and punchy climbing.