Bike-wise we put the wheels on BH’s top-tier G7 Disc aero road bike. The same bike that was destined for a Spring Classics campaign, before the probably rash removal of disc brakes from the pro peloton, the G7 offers a stiff platform that was well suited to a mid-depth wheel and fast rolling tire. It also was developed with rough cobbled classics in mind and uses tiny seatstay to try to minimize the strain on a riders lower back that often accompanies deep carbon rims.This setup had us running the wheels with 12mm thru-axles front and rear, and tires usually inflated to anywhere between 75-90psi (5.2-6.2bar) for our 155-175lb/70-80kg testers, depending on the anticipated road surfaces. For the off road sections of our tests we paired the 404s to some Challenge Chicane open tubular clinchers, also with latex tubes. Most of our ride time was spent on a custom-built steel cyclocross bike that let us swap the end caps over for use with quick releases. The cross tires measured out pretty close to their claimed 33mm width, so you shouldn’t run into any trouble mounting up regular cyclocross tires to race.Our cross testing was pretty much limited to sandy areas, some asphalt, fine gravel, and relatively smooth cobbles, so tire pressures stayed right around 30psi (2bar).Tech Details The wheels have a claimed weight of 1715g, but our sample set weighed in at 1785g for the pair including the 12mm axle end caps and cloth rim strips installed. The clincher 404 Firecrest DB wheelset retails for $2400/2500€/£1920.Ride ReviewRiding the 404s on a disc brake bike, the first thought was that the Firecrest shape really does live up to the hype and the wheels do make you feel fast. They perform very well, especially when riding into a headwind that would otherwise feel like it was sapping your power. One of our testers even went so far as to say that in the right wind conditions it felt like they were pulling you along like a sail. The standard Swiss steel bearings also roll very smoothly and combine with the aerodynamic advantage of the rim shape and texturing to really give a sense of easy speed.That said, riding them into a crosswind is a completely different story. While a steady crosswind was manageable, the wheels make a bike scary when riding in gusty winds or on descents where the wind picks up or changes direction. Even though Zipp did a lot of pioneering in the improvement of the handling of deeper wheels with wide tordial profiles, these still resulted in several white-knuckle sections of road when we were riding at high speed.Wind was never an issue during our off-road riding. That was partially just that we lucked out, riding on more calm days, but also riding at lower speeds on loose surfaces the wind effect was less dramatic and our attention was always more focused on line choices through deep sand and over sand-covered cobbles.As with any wheel with rims close to the same depth, the 404s felt pretty stiff. They definitely are not a comfort wheelset. But we spent a good bit of time riding on a variety of cobblestones and traditional pavé, and have to say that the wheels deserve to be paired with nice supple tires and latex tubes so you can run as low a tire pressure as possible to balance comfort and grip. We managed to keep from bottoming out the tires, but the Firecrest Carbon Clincher rims do have a fairly wide and rounded bead hook that will likely let you get away with the (very) occasional bottoming with less risk of pinch flats. We had zero flats in a couple months of riding. The only downsides (beside a high price) that we felt on the wheels were mostly to do with the hubs, and in a couple of cases due to their ease of use/service. At one point we weren’t able to get the thru-axle end caps to sit perfectly straight without tools, so it required some extra effort to install the wheel and get the thru-axle through it. Once it was properly tightened down, it was fine and the bearings spun smoothly, with no more issues.The other ease of use annoyance was the removable freehub body. Much like on DT Swiss hubs, if the hub does not have a QR holding it together and you lean the wheel cassette side down, the freehub will fall off. Sure this isn’t something that will happen much on a road bike, but for cyclocross where wheel swaps are frequent, it is going to happen if you aren’t super careful. That is then compounded by the fact that the small pawls and springs like to jump off into the dirt/mud/sand and must be cleaned and relubed before reinstalling, at which point it is rather difficult to do with the cassette installed and requiring a long thin tool to help the pawls back into the hub shell. Overall the hub engagement doesn’t seem to quite live up to the rest of the wheel’s performance either.All that said the performance of the wheels certainly outperforms any nits we found to pick with the hubset. They tracked straight on both road and cross bike and really made us feel fast. At two and a half grand it’s hard to say that they offer free speed, but if you have the budget to ride them, there are few better options to upgrade your disc brake bike for improved aerodynamics, unless of course you can commit to the tubulars to get a wider and even more comfortable tire profile.Zipp.com We started out on the road with some lightweight clinchers and an aero road bike. For that we paired the 404s with Vittoria’s fast-rolling cotton tubeless clincher Corsa Speed time trial tires. Since the Zipps are not tubeless-ready, we put in some latex tubes to get the most out of low rolling resistance and to get away with slightly lower tire pressures in the 23mm tires. Mounted on the 404s, the Corsa Speed tires measured out to about 25mm which thankfully added a bit of volume for the rougher roads that were in store. We covered the tech on the wheels in depth back in April, but as a slight refresher they are composed of Zipp’s 58mm deep, 16.25mm internal full carbon clincher rim mated to Zipp’s 6-bolt 77/177D aluminum hubs. Both wheels get 24 Sapim CX-ray CX-Sprint spokes and while the rim is not a new shape or profile specific to disc brakes, they do not get a brake track, so are disc brake ONLY.The hubs use a tool-free removable freehub body (we used the typical 11 speed Shimano body) and tool-free interchangeable end caps. Both sets of end caps were included with the wheels. Back in the beginning of the spring Zipp introduced a pair of new aerodynamic wheelsets to suit the needs of the growing number of aero road bikes coming to market. There might have been speculation at the time of really what kind of bike would pair something like their deepest aero 808 rim to disc brakes, but we’ve since seen a number of suitable aero bikes make their debut. Here at Bikerumor though, our thoughts then were mostly to a wheelset that could handle more everyday type riding, so we got our hands on a set of the mid depth 404s to see how they rolled. While Zipp has proven their aero carbon tubulars on the cobbled classics and, in their disc brake guise, on the cyclocross circuit, we wanted to see how the slightly deeper 404 in a carbon clincher could handle both, making it easy to switch tires (and axles) to suit multiple disciplines….