Zipp says it is the company’s fastest disc ever due to the use of said tires and extensive research and development into the transition between tire and rim.
The new disc has seen nearly two years of development, including race testing under Tony Martin. Martin rode the wheel to a silver medal in the Olympic time trial, a second world TT title, and a crop of other international podiums — as well as a few flat-tire disappointments at the Tour de France.
The Super-9 uses the same brake track technology as the rest of Zipp’s successful range of carbon clinchers, employing high-temperature resins to prevent the tire blowoffs associated with the industry’s early carbon clincher efforts. That carbon brake track, which we are warmly familiar with following our recent testing of Zipp’s 202 Firecrest Carbon Clincher, offers industry-best dry braking performance with excellent outright power and modulation. It is as close as we’ve found to the performance of an aluminum brake surface when dry.
By going with a carbon clincher, Zipp could carefully shape the brake track to provide a smoother transition from tire to rim — an area that seems to be the next frontier in gaining aerodynamic advantages. Wheel giant Mavic has focused on this area as well, introducing its CXR80 wheelset with small rubber strips intended to completely flatten the tire/rim transition.
While Zipp hasn’t taken tire integration that far, it has spent quite a bit of time perfecting its own brake track. On the Super-9 CC, the two sides of the brake track are not parallel; rather the tips point inwards slightly, and the disc bulges out to its widest point just below the brake track. Following the trend of Zipp’s other carbon clincher offerings, the tire bed is very wide: The center of the brake track is 26.42mm wide and the widest point on the disc is 27.5mm.
Zipp says the disc is still optimized for a narrow tire, 21 or 23mm wide, but because of the shielding effect of the frame running a wider tire won¹t do as much damage to the aerodynamics as it would on the front wheel.
“Since most modern tri’ or TT bikes have a seat post that blocks the leading edge of the disc, it is a bit more ‘tire agnostic,’ let’s call it. You can run a 25mm tire, for added comfort or tire protection, with far less of a penalty since you are only affecting the [air’s] exit speed, and not the overall laminar flow characteristics across the entire disc surface,” explained Zipp’s David Ripley.
The disc that arrived last week at VeloNews.com World Headquarters last week weighs only 1088 grams, significantly lighter than the claimed weight of 1175g. The disc is adaptable for track use, and features a max weight limit of 275 pounds plus a max tire pressure of 125psi. The 188 disc hub is compatible with both 10- and 11-speed drivetrains.
The budget-conscious need not apply: price for a rear disc is $2,375.
The Super-9 Carbon Clincher is heavier and more expensive than virtually the same disc in its tubular version. So, why bother?
The short answer comes in two parts: First, it is possible to produce thin clincher tires with lower rolling resistance than any road-capable tubular (some track tubs may be a bit faster); second, there are aerodynamic gains to be made by perfecting the tire/rim transition with a clincher tire that are not possible with a tubular. The additional weight is far less relevant in a time trial than it is in a road race.
That is why Tony Martin and his Omega Pharma-Quick Step team worked with both Zipp and Specialized to design wheels and ultra-light, ultra-low-rolling-resistance tires for big competitions. If one is concerned purely with rolling resistance and aerodynamics, clinchers are the best option, they say.
So why are clinchers still so rare in the pro peloton? They won’t be for long — in time trials, anyway. In addition to Martin’s well-documented clincher use, BMC Racing’s Taylor Phinney rode with a rear clincher disc at the Olympics and worlds this year, and other time trialists will be jumping on the bandwagon this year. With the introduction of Bontrager’s deep carbon clinchers, don’t be surprised if you see Spartacus rolling on clinchers next year, too.
For road racing, the tubular is still king, and will be for some time. That is because there is a host of additional concerns on top of simple speed. The weight of a tubular system (rim, glue, tire) will generally be 100 or more grams lighter than its equivalent carbon clincher system weight (rim, rim tape, tube, tire). But even more important than the weight, tubulars allow a racer to continue to ride on a flat tire. Often they’ll ride for miles, a bit more slowly, of course, while they wait for a team car to catch up. And, because tubulars are glued on, and thus won’t fall off when deflated, that racer is more likely to stay upright when the flat first occurs.
Tubulars also tend to provide a rounder profile than clinchers, although that is changing as rims widen, rounding off clincher profiles. A rounder profile usually allows for better, more predictable cornering. The ride quality of tubulars is generally considered to be better than most equivalently durable clinchers as well.
And, of course, there is good old tradition. When you hear of European pros running 145psi, it’s clear that custom and folklore still wield significant power.