Review: Mavic Cosmic Carbone 40C Carbon Clinchers


Now The Bad News

Carbon and aluminum working together.

During its initial presentation of the new Cosmic Carbone 40C, Vestal admitted that Mavic never wins the weight war because they “focus on durability.” And indeed, at 1545 grams per pair, these hoops wont wow any of the weight weenies out there.

On the plus side, the 40C requires no rim tape, which is a net gain of 30-40 grams depending on which brand of tape you choose. For example, Velox cloth rim tape is listed on several websites at 16 grams per wheel, while SRAM-branded nylon tape is listed at 18 grams per roll. By comparison, Zipp’s 303 Firecrest has a claimed weight of 1475 grams and the Reynolds 46mm clincher comes in at a claimed 1440 grams, but both require rim tape during set-up.

Mavic also claims that due to their new wheels’ unique design, the Comic Carbone 40C rims have exceptionally low inertia weight (think lower rolling resistance). Obviously we couldn’t verify this during our short test time, but that’s part of the message so we’ll pass it on.

Where these new wheels don’t make up ground is in depth and width. The 40C are 40mm deep versus 45mm and 46mm for the Firecrest and Reynolds. And the 40C’s width is listed at 19mm wide, which is also less than the competition. Mavic’s rationale here is a common refrain – safety first.

“Aerodynamics are generally enhanced by a wider rim,” admitted Vestal. “But in the case of 40C, Mavic’s first goal was to make a reliable, safe carbon clincher that brought some genuine performance benefit, including lighter weight, low inertia and low rim weight. The top 40C design goal was to keep the rim as light as possible for low inertia without sacrificing durability. By contrast, many carbon clinchers require overbuilding of the rim to withstand brake heat and radial impacts. So, any aero benefit of a wider rim wasn’t top priority.”

Mavic says these wheels were in development for three years.

Certainly plenty of consumers wont buy this explanation, since the primary reason they want a carbon clincher is for enhanced aerodynamics without the hassle of gluing tubulars. But Mavic is convinced many other would-be carbon clincher buyers will be won out by the all-purpose reliability and decent aero numbers of the 40C.

“When the Ksyrium wheels were introduced 12 years ago, they were hailed as the all-purpose, do everything wheel solution,” said Vestal, alluding to Mavic’s longtime flagship alloy wheel. “They also earned a reputation for long-term durability. Well, these new wheels are meant for the same rider who wants one pair of wheels to do everything, every day. On top of that we believe our rim shape is actually quite good in the wind, especially across a wide range of wind angles. It’s not the fastest wheel at every yaw angle, but it’s quite stable at extreme yaw, which is a benefit.”

Obviously, we did not have a change to run these wheels through a battery of wind tunnel tests, but in the light winds we encountered during test riding the wheels were never overly buffeted.

About the author: Jason Sumner

An avid cyclist, Jason Sumner has been writing about two-wheeled pursuits of all kinds since 1999. He’s covered the Tour de France, the Olympic Games, and dozens of other international cycling events. He also likes to throw himself into the fray, penning first-person accounts of cycling adventures all over the globe. Sumner, who joined the / staff in 2013, has also done extensive gear testing and is the author of the cycling guide book "75 Classic Rides: Colorado." When not writing or riding, the native Coloradoan can be found enjoying time with his wife Lisa and daughter Cora.

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  • Sandro says:

    Jason Sumner
    The Mavic Cosmic 40C is faster inertia in climb?

  • gkuch says:

    Love your photo from Mars Hill!

  • Bryan girton says:

    No catastrophic failures in four rides? I guess that would be a priority for any wheel manufacturer. $2700 for a wheelset that’s not super light or super aero and squawks when hitting the brakes? I don’t understand the aero wheel crowd, and especially how they would pay that kind of $$$ for little if any benefit over a good set of aluminums. I’ll stick with my “old skool” kysrium sl’s (tubeless) thank you, they’ve been a great wheel at a reasonable price.

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