Ingezonden

After already being raced for about a year under the Garmin-Barracuda team, Mavic finally announced the release of the new Cosmic CXR 80 aero wheels. According to Mavic’s testing at the wind tunnel in Geneva – which we were on hand to witness – the new Cosmic CXR 80s produce substantially lower drag than Zipp’s 808 Firecrest (James Huang/BikeRadar)

Mavic on Sunday launched a
wheel the company is calling the “most aerodynamic in the world,” with a
uniquely integrated tire system called CX01 (pronounced “see ex one”).

The new Cosmic CXR 80 has a
novel 80mm-tall rim profile featuring channels for plastic ‘blades’ that snap into place and dramatically smooth the transition between wheel and tire. Garmin-Barracuda raced the wheels to victory in last year’s Tour
de France team time trial. Mavic claims this wheelset is so fast that it will unseat
the current benchmark of aero speed, the Zipp 808 Firecrest.

Not just a wide profile

It
should come as no surprise that Mavic’s new Cosmic CXR 80 carbon tubular rim is wide, measuring a generous 27mm across
at the tire bed, with a maximum width of 28mm about a third of the way down the
profile. However, it’s how that profile is integrated with the matching tire
that produces the impressive wind tunnel figures.

About
4mm of that width at the tire bed is dedicated to a channel on either side for
the new CX01 ‘blades’ – nearly weightless plastic strips that snap into place to
produce a smooth  transition between the
tire sidewall and rim. When combined with the slightly altered casing profile
and special tread texture of the matching Yksion CXR tire, the result is a NACA
0024 airfoil
profile on the leading side of the wheel and a truncated airfoil
one on the trailing side.

Mavic’s
wind-tunnel data suggests modest aerodynamic gains over a Zipp 808 Firecrest at
yaw angles up to about 10 degrees. However, Mavic’s data also suggests that the
808 begins to stall out at that angle while the drag for the Cosmic CXR 80
continues to drop. When the Cosmic begins to stall at 18 degrees – and where
the difference is most dramatic – Mavic claims a 6.4W energy savings at 50km/h
(31mph), which translates to 15 seconds saved over a 40km time trial or a
whopping 1′ 10″ for a full Ironman leg.

Compared
to Mavic’s Ksyrium, the advantages are even more dramatic: 20 watts, 49
seconds, and more than four minutes for the same conditions.

Attention
has to be paid to those novel ‘blades’ that smooth the transition between tire
and wheel. Garmin-Barracuda used them for a bit last season — until the UCI
at least temporarily banned them, pending further investigation. Mavic’s tunnel
data suggests that the blades’ biggest effect is on stall angle, which drops to
about 14 degrees when they’re removed. Up until that point, however, the blades
don’t appear to make a difference.

Plastic ‘blades’ snap into a channel in the rim, dramatically smoothing the transition between wheel and tire

So
does this mean the Cosmic CXR 80 is really faster
than the Zipp 808? Well, yes and no. Mavic’s wind tunnel data reveals only
a modest advantage over the Zipp up to 10 degrees of yaw. However, the
divergence of the two curves past that point suggests that the new Cosmic is
faster over a wider range of conditions, plus the gentler upswing hints to more
predictable handling in swirling wind.  

Aerodynamic
benefits aside, the new Cosmic CXR 80 looks to be a capable wheelset in other
key performance areas. Total claimed weight without tires is a respectable
1,630g (725g front; 905g rear; 2,170g with tires and blades) so they’re still
useful on moderately hilly courses. The sleek carbon-bodied hubs feature reasonably
wide aluminum flange spacing for good overall stiffness. Standard straight-pull
bladed stainless steel spokes and external nipples are used for easier
servicing. And the hubs use a similar internal layout to Mavic’s current
design.

Pricing
is still to be determined but availability is projected for late summer.

Testing, testing, testing

It’s
commonplace for aerodynamic wheel launches to be accompanied by pages of wind
tunnel data (which invariably show the presenter’s new model to be the best of
the bunch). However, Mavic chose to launch the Cosmic CXR 80 at the actual wind
tunnel in Geneva, Switzerland, where the testing was done, and we were able to
watch some of the testing.

In
fairness, we at BikeRadar don’t have
sufficient technical knowledge to determine if the Geneva tunnel’s protocols genuinely
replicate real world benefits or if the programmed algorithms generate truly
accurate drag data. However, it’s difficult to find fault with the relative inflection
points of the Cosmic CXR 80′s and the Zipp 808 Firecrest’s respective curves
that were generated right before our eyes.

Mavic spent more than 400 hours in the wind tunnel last year

Mavic’s
claims at least seem believable and
given the length of time that the company has delayed really getting heavily
into the aero playing field, one would at least hope the company is doing it
properly, particularly given the amount of time invested. According to Mavic,
the spent more than 400 hours of wind tunnel time spread out over eight
sessions in 2011 alone.

The
facility also built a separate “stress balance” specifically
dedicated to bicycle use – supposedly the only bike-specific test stage in the
world – and claimed resolution is on the order of a single gram of drag. Mavic
themselves even built a special widget that measures and records relative yaw
angles and wheel rotation speeds in real-time – while riding.

For
that kind of investment, the new Cosmic CXR 80 had better be good. We’ll find out for sure when test samples arrive
later this month.

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