It wasn’t so long ago that the sub-1000-gram wheelset market consisted of one brand: Germany’s Lightweight. They were such hot commodities that some of the sport’s biggest stars were shelling out thousands of dollars to get a pair. In the ensuing 10 years, a few more brands have introduced wheels at similar weights, but with price tags close to $6000. That has all changed now that Mercury has unveiled their 929-gram MZero wheelset, which boasts greater serviceability and a price tag half their counterparts’s.
Up until now, the few wheels falling in the triple-digit weight range have been a “wheel system,” with carbon rims, spokes and hubs bonded together— which doesn’t allow for any type of wheel truing or spoke replacement. The MZeros go about it differently. First, Mercury found a hub set that had the potential to deliver a wheel in the targeted weight range. Boulder, Colorado-based Dash crafts their carbon hubs inhouse, which weigh a paltry 145 grams for the pair. They achieve this by using carbon shells reinforced with aluminum rings at the spoke interface and oversized carbon axles. The rear hub uses a titanium drive ring with protruding tabs, which double as the driveside spoke flange. A heavily machined alloy freehub body sheds all unnecessary material from the already scant hub. Steel bearings come stock in the hubs, but a ceramic upgrade is available for $200.
It may be that the Dash hubs are the most spectacular feature of the wheels, but it’s the Sapim stainless steel spokes that make them more practical than the bonded carbon spokes of their competitors. Using a traditional spoke allows for replacement and wheel truing, which isn’t possible with the others.
The third component in the MZero wheel design is the carbon rims, which utilize the latest in carbon-design philosophy. Each of the 275-gram, 30mm-deep rims have a rounded, blunt nose shape for aerodynamics and crosswind handling, while the 25mm width adds stiffness and tire stability. The 23mm-wide Kenda Volare tubulars we mounted were fully supported by the width of the rim. The tires’ sidewalls don’t bulge wider than the rim as they do on narrower rims.
Never borrow a pair of these wheels for one ride “just to try”—it will be ingrained in your head how unbelievably huge the difference is between these and a pair of…well, almost anything else. We found ourselves out of the saddle for long stretches of time, grabbing gears that are usually reserved for the flats.
While the wide rims help give the wheels lateral stiffness, it unfortunately comes at the expense of damping the road’s imperfections. Even the Kenda Volare’s suppleness wasn’t enough to conceal the MZero’s unforgiving ride.
Due to their stiffness-to-weight ratio, the MZeros are an anomaly for an ultralight climbing wheel. Simply put, these wheels are in a league of their own. The 25mm-wide rim profile not only helps with the cornering rigidity, but it also gives better stability for the entire width of the tire. The front hub’s widely spaced spoke flanges help it attain the cornering stiffness that was much appreciated at higher speeds.
Due to the rounded shape of the rim’s nose, the brake track doesn’t have a perfectly flat surface for the pads to grasp; this leaves about 20 percent of the brake pad unused. Using the included carbon-specific pads, braking power was on par with other carbon tubular wheels, even with the rounded rim shape.
Just like on the climbs, crosswinds are something the MZeros don’t have to worry about. When hitting such a low weight, wind gusts could easily blow a lightweight pair of wheels off track, but due to the low 30mm depth and rounded nose, the wind has little surface area to disturb.
Although the MZeros feature replaceable spokes and have the ability to be trued, they are still very much a specialty wheel to be used on certain occasions. We’ve put them through the ringer on our various training rides without a hitch, but with their extreme weight-saving features (like the carbon axles), the MZeros are not intended for day-in-and-day-out riding.
Enlisting a multitude of materials, the Boulder, Colorado-made Dash rear hub uses carbon, titanium and aluminum in its construction. Adding another material to the mix are the stainless steel spokes.
Spending $2900 for a special occasion wheel is a luxury few get—and not all would want. But as frivolous as it may seem to some, the performance benefits the MZeros possess make them justifiable to racers looking for mechanical enhancements.
Even though they’re not the smoothest-riding wheels available, their stiffness-to-weight ratio—in addition to their ability to be trued—lands them on top of the podium in the sub-1000-gram wheel competition. Even with Mercury’s entry into the ultra-high-end market, they’re still making a full line of carbon and alloy wheels that are designed for training, racing and everything else.
-Weight: 929 grams, plus 58-gram quick releases
-Rim depth: 30mm
-Rim width: 25mm
-Spoke count: F-20/R-24
-Spoke type: Sapim CX-Ray stainless
-Spoke pattern: F-radial/R-radial non-drive side, 2x drive side
-Notes: Available for Campagnolo and Shimano/SRAM. Includes brake pads, quick releases and padded wheel bags.