Just In: Mavic Cosmic Carbone 40C Carbon Clinchers

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Author’s Note: This is not a full review. Please do not treat it as such. Instead the objective is to illuminate Mavic’s claims about its new carbon clincher wheels, and present our very preliminary impressions (aka: one test ride). RoadBikeReview will have these wheels for an additional week before returning them to Mavic, and will present follow-up impressions soon after.

The carbon clincher is a curious beast. Over the years it seems to have created equal parts ecstasy and agony. They look great and allow users to reap at least some of the benefits of carbon aero wheels without the headaches of gluing and maintaining tubulars.

But they also have drawbacks. Unlike aluminum, carbon fiber does a poor job of dissipating heat, and that can be a real problem when you’re bombing a long descent. You grab the brakes, heat builds up, and the next thing you know you’re on the side of the road repairing a flat — or worse.

In February 2012, organizers of the popular Levi’s Gran Fondo went so far as to ask participants in the popular, mass-start amateur road ride in Northern California to not use carbon clinchers at the event. “Please leave them at home,” read the communiqué. “Carbon clincher wheels are strongly discouraged because they can fail/explode under the extreme braking necessary on sections of this route.”

Of course anyone who’s ridden Levi’s ride knows that there are some extremely steep descents, making this request at least in part a case of Cover-Your-Ass diplomacy. But there’s no denying that the carbon clincher experience can be interesting if nothing else. Warped rims, sometimes dubious braking effectiveness (especially in the wet), tire blowouts, and the ever-present shrill can leave you questioning whether the convenience and aero efficiency is worth the trouble.

But that’s a debate we are going to steer clear of. Love them or loathe them, carbon clinchers are here to stay. And the new Mavic Cosmic Carbone 40C’s are a player in that market.

The Mavic Party Line

During our one-on-one sit-down with Mavic PR man Zack Vestal on March 20, he walked us through the chronology that brought us to this point. That story started with an explanation on why the famed French wheel maker was so late to the party, as this is Mavic’s first carbon clincher wheelset. (Actually they are a carbon-alloy hybrid, but more on that later).

“The reasons boiled down to the engineering challenges of maintaining structural integrity, withstanding braking heat, and coming up with a solution that is actually beneficial in terms of weight and rim shape,” he said. “We’ve seen many examples of carbon rims being flared out due to heating of the clincher bead, and the reality is that after some time, the industry has recognized that they are not the best wheel choice in all situations.”

Of course some of this is truth, some is PR speak, and some of it is Mavic being Mavic. Early adapter is not necessarily part of the company’s mission statement. But they do have a long history in the wheel-making realm, so some benefit of the doubt is warranted.

Whatever the case, after three years of development, the Mavic Cosmic Carbone 40C was born. Retail price is $2,750 and they’ll become available to the North American public starting June 1. They are 40mm deep, 19mm wide, and weigh 1545 grams per pair, which as any wheel aficionado knows, is a decidedly middle-of-the-road number in this game.

“We never win the weight war because we build durability,” explained Vestal. “Weight was not the driving motivator. Building a safe, durable, nice riding carbon clincher was the goal.”

For comparisons sake, which Mavic did a lot of during the presentation, Zipp’s 303 Firecrest 45mm carbon clincher weigh a claimed 1475 grams and the Reynolds 46mm clincher comes in at a claimed 1440 grams. However, as Mavic was quick to point out, these numbers do not include rim tape, which their new wheels do not need (more on that soon).

“That can be 25-30 grams per wheel or more,” said Vestal. “So the differences are not as big as they might seem.”

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 in British Columbia, Belgium, Brazil, Costa Rica, France, and Peru among many others. Sumner, who joined the RoadBikeReview.com / Mtbr.com staff in January, 2013, has also done extensive gear testing and edited a book on cycling tips. When not writing or riding, the native Coloradoan can be found enjoying the great outdoors with his wife Lisa.


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  • H A Turner says:

    If you ever ride the MadFiber wheels in a steep, gusting cross-wind, you’ll regret it! They are unbelievably bad in gusty cross-winds. I own Zipp 202s, 303s, 404s, and 606s. I also own Reynolds DV46 (tubulars and clinchers), Williams 60mm, and Mavic Ultimate tubulars. (Yes, I know, I have a wheel sickness and need help!) The MadFibers are, by far, the worst of this group in gusts from the side. They are right up there (down there?) with the 8-spoke Spinergy wheels of several years ago.

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