Cosmic Pro Carbon SL UST Disc Wheel
While tubeless setups are the norm on mountain bikes these days, it's adoption for road biking has taken a much slower approach. Roadies are often seen as traditionalists and maybe even a bit stubborn, and to some extent, so is the French wheel crafting firm Mavic. Notably slower to the road tubeless game than others, it insisted on a healthy amount of research and development making sure that the safety and reliability of the setup were critically dependable. It seems a bit odd that the pioneers of the industry's first tubeless rims, the Crossmax, took so long to get on board, but in use, compared to the massive pain of setup that we've seen from other tubeless designs, we feel it was well worth the wait. We're so excited to get some saddle time in on its Cosmic Pro Carbon SL UST Disc Wheel, as it completely checks off every criterion we seek in a modern road wheel.
This lightweight wheelset takes road tubeless to the next level. As with most tubeless setups, it reduces weight, puncture potential, and PSI for less rolling resistance and more comfort. The deviation comes in ease of installation: the tires pop-on without tire levers and inflate without a compressor, CO2, or high-volume floor pump. Just use the same old floor pump you top off your tires with before every ride, though we do recommend sticking with Mavic's UST-specific tires, which come stock on the rims.
Some of us were under the impression that Mavic was sitting on the backburner while the road tubeless scene started to boom, but with the unveiling of Road UST, it is evident that we couldn't have been more wrong. Instead, it's apparent that there was a certain level of patience and discipline exhibited while Mavic's engineers were hard at work perfecting the technology, prioritizing safety and ease of use before release. The result is a tire and rim interface that was designed in conjunction with one another, harnessing all of the benefits of tubeless that we crave, like lower rolling resistance and puncture resistance, and skipping the downside that has most cyclists complaining, namely, tire installation. Since road tires require much higher pressures and sit on narrower rims, the tolerances must be tighter than on MTB wheels, so Mavic took its time until total satisfaction was achieved, with less than a millimeter of tolerance on the tire that assures you the tire will go on with ease, and stay on.
Of course, some of us found frustration from this level of perfectionism, though that kind of stubbornness and patience is only negative if you value industry trends over proven, effective, and safe technology. To illustrate the point, consider that at a recent sportive event associated with that big race in France, Mavic reportedly provided neutral service support for 38 instances of carbon clincher failures. This tells us what Mavic knew all along: delamination, deformation, cracking, and the like are all still common occurrences in the carbon wheel world. To deal with this, Mavic has long used aluminum inserts in its carbon wheels to serve as reinforcing spines and heat sinks. The risks of full-carbon rims were unacceptable to the brand, which is built on reliability, safety, and longevity as much as it is low weight and aerodynamics, all of which are reasons why generations of cyclists have been grateful for that stubbornness. Of course, these wheels are disc specific and serves the burgeoning market of road disc bikes which eliminates the need for heat management and additional pressure applied at the rim's braking surface, however, it's nice to know that the same technology instilled in its rim brake rims carries over to a disc rim with fewer demands to handle.
The rims feature a new aerodynamic profile that Mavic claims compares favorably to some of our top-selling wheels in the 40-50mm range. The French brand credits the Cosmic Pro Carbon SL with saving 2.3 watts across yaw angles up to 10 degrees, which means the aerodynamic properties don't disappear as soon as you take the wheels out of the wind tunnel and onto the actual roads. The new profile is less pointy than Mavic's usual models. Instead, it features a dramatically blunted inner face and represents the most radical departure from a pure NACA airfoil shape from the stubborn French firm to date. The shape better manages oblique resistance, combining the aerodynamic benefits of deep rims with additional crosswind stability.
With all the excitement about the new rims, it's easy to overlook the Cosmic Carbon SL's Instant Drive 360 hubs. The hubs represent yet another drastic departure from tradition, as the engagement mechanism replaces the usual pawl system with the dual-ratcheting rings formally found only in designer hubs on custom hand-builts. The design involves two rings that press together laterally. One face of the rings' teeth is sloped, so they ramp off of each other while freewheeling. The other face isn't, so the rings engage with pedal input. The design cuts the engagement angle down to nine degrees, a number we might expect to see on a mountain bike hub but are pleasantly surprised to find on the road.
The wheels ship with front and rear quick-release adapters as well as a tubeless syringe, sealant, rim tape, and valves. It also ships with Mavic's 25mm Yksion Pro UST tires for the front and rear, ensuring you hit the road with the exceptional attention to detail that went into crafting the wheels.
- Perfection meets road tubeless in this racing wheelset
- Mavic's all carbon rim construction prioritizes safety
- Rim and tire developed together for effortless installation
- Centerlock disc braking improves stopping power and modulation
- Tubeless is more efficient, comfortable, and punctures less
- Yksion Pro UST tires mount by hand without tire levers
- UST interface seats compatible tires with a standard floor pump
- Mavic proves again why it's the first and last name in wheels