Cosmic Pro Carbon SL UST Wheel
If we were to choose one descriptor to apply universally to Mavic, it might be "stubborn." There are negative and positive implications of the brand's stubbornness, and the new Cosmic Pro Carbon SL UST Wheel reinforces the positives while dispelling the negatives. The positive aspects of Mavic's stubbornness are that the brand is obsessed with safety and durability to the point where it won't compromise either in pursuit of fads. Mavic wheels simply refuse to fail because the brand refuses to gamble on new tech for the sake of newness alone. This leads to the negative aspect: Mavic has been criticized for apparently lagging behind the so-called "innovative" manufacturers because of that stubborn refusal to immediately adopt whatever new tech happens to catch the industry's collective fancy.
Of course, that kind of stubbornness is only a 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.
The brand poached an engineer from the aerospace industry, one Jean-Christophe Minni, and gave him two years to develop carbon fiber technology that would allow it to assuage its own concerns with the safety of composite materials. The full-carbon Cosmic Pro Carbon SL UST Wheel is the result. Minni's construction process produces rims that can withstand a claimed 392 degrees Fahrenheit before the resin begins to detach, and Mavic claims that braking tests on descents like Mont Ventoux and the Col de la Madone — which blend tight switchbacks and long, sweeping sections — don't cause rims to approach that threshold. This towering tolerance may seem like overkill while you're sitting on the couch browsing Competitive, but we can confirm that it's very reassuring during 20-minute descents that require a bit of brake drag. And that's why Mavic is such a trusted name in the cycling industry. They leave nothing to chance.
While that heat resistance is mostly about improvements to the resin, deformed rims aren't the only wheel failure woe Mavic's iTgMAX technology addresses. The all-important layers of material in the tire bed are wholly intact. There's no cutting fibers, no Frankensteining, no creative gap filling, and no machine finishing. By keeping each layer intact and not disturbing the finished product, Mavic reduces the chance of introducing the artificial weak points that plague piecemeal carbon lay-ups, maintaining a solid surface for increased structural integrity. Instead of a puzzle of carbon fiber scraps glued together with resin, the carbon is already a unified piece.
The brake tracks themselves are finished with lasers. Our shared cultural imagination typically treats lasers as precision finishing instruments, tools applied with a surgeon's delicate discretion in order to meet impossibly meticulous manufacturing standards. The opposite is true for brake tracks, though, as Mavic uses the lasers in order to literally rough the rims up. The lasers are the sci-fi equivalent of sandpaper, removing the outer, smooth layer of resin to expose a more erratic texture that better grips the soft, SwissStop Yellow King brake pads shipped with the wheels.
And we should stress that the Mavic-yellow pads are soft. Given that softness, a fair amount of sloughed-off material in the form of yellow powder and more frequent pad replacement is the only immediately obvious downsides to the wheel's exceptional braking. Mavic claims harder, more durable pads will work, but we strongly discourage it as they may damage the rims. We like the idea of the pad shredding much better than the rim shredding. Plus, the harder pads won't be yellow.
When the pads engage the exposed fabric of the rims' brake tracks, the wheels emit a sound like the whir of a jet engine heard at a distance. It's a reassuringly positive indication that the brakes are engaged, and the sound is especially welcome as a warning to those around you while riding in a group or pace line. It's not unlike the sound of Mavic's Exalith brake tracks — the French brand's version of brake lights for bicycles.
Given how responsive the braking is, that signature whirring is almost a necessity. With each new generation of carbon wheels, we're bombarded with claims of carbon braking that's so good it rivals or is better than alloy brake tracks — you know the drill. This time, those claims are actually true, and we suspect it's another part of the reason why Mavic took its sweet time sending the full-carbon rims to market.
Mavic's obligatory quantification of improvement is limited to braking in wet conditions, where the brand claims that stopping distances are reduced by 50%. Braking in dry conditions is equally impressive, and — once the pads and brake track have had a ride or two to get intimately acquainted — stopping on the full-carbon Cosmic Pro feels akin to Mavic's alloy offerings. It may not rival Exalith, but this is one of the most confidently responsive brake tracks we've tried.
In addition to the improved braking, the rims also 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 claims the Cosmic Pro Carbon SL UST Wheel saves 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 Pro Carbon SL UST Wheel'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.
Internal rim width is one area where Mavic remains stubbornly dug in. The Cosmic Pro Carbon SL UST Wheel is 19mm, internally, which is at odds with the trend of 20mm+ internal widths cropping up like weeds. Mavic's reasoning is simple: The International Organization for Standard (ISO) actually only recommends those expanded widths for use with tires much larger than what we typically ride and race on. For 25mm tires — the new standard — ISO recommends a maximum internal rim width of just 19mm for rims with bead hooks, so those exaggerated internal widths actually aren't in compliance unless you run tires upwards of 30mm in diameter. There are structural benefits to greater external width, though, and Mavic takes full advantage of that fact by blowing the Cosmic Pro Carbon SL UST Wheel's outer measurement up to 25mm. Stubbornly safe, as always.
As mentioned above, the wheels ship with Mavic-branded SwissStop Yellow King brake pads. We recommend only using this model of pad. The axles are hollow, which allows for conversion to different axle standards by using various end caps. The wheels also ship with Mavic's Yksion Pro UST tires in the front and rear.
- The stalwart Cosmic improves its braking and aero profile
- Blunt-faced rim profile improves crosswind stability
- Mid-depth profile slices through the air and improves stiffness
- New hubs rival those found in hand-built, custom wheels
- Get out on the road fast with included Yksion Pro UST tires
- Mavic delivers bombproof reliability in a race-ready package