Roval 321 Disc – First Look

We knew it was coming. We just didn’t know when, or what it would be called. Meet the Roval 321 – a wheel we first saw July of 2017 in the Tour de France and have been asking Specialized about ever since.

The Roval 321

Before we get into the specs, let’s talk trophies. For a wheel officially introduced this week, it already has racked up a pretty impressive set of victories:

  • Tim Don set an Ironman record in Brazil on the wheel in May 2017.
  • Maciej Bodnar won the stage 20 Time Trial at the 2017 Tour de France.
  • Javier Gomez rode to a win at Ironman 70.3 Worlds in September 2017.
  • Lucy Charles won IM South Africa in April 2018.

Development started on the 321 back in 2015 when athletes started taking renewed interest in the Hour Record due to UCI rule changes. The 321 Disc wheel was initially intended to be a one-off prototype to fit in a special, custom frame made for the attempt. Because of this, Specialized (Roval is the in-house components arm of Specialized) engineers had remarkable freedom in developing a unique shape and this early thinking led to the final asymmetric lenticular design that we see today.

The shaping of the final rim was therefore adjusted to ensure a proper fit in most of today’s TT and triathlon frames. The main drivers of the aerodynamic shape remain, however. The left lens has a single large curve for aerodynamics and the ideal level of stiffness. The right lens, meanwhile, has three features within its shape that are noteworthy. Near the tire region, the shape is wide with an ideal curvature for airflow around the tire, while the midsection is sucked inward for cassette and rear derailleur clearance. And finally, where it meets the hub, it kicks outward again for a wide stance and improved stiffness.

Specialized utilized an exclusive 1k carbon fiber and monocoque molding design to achieve their final targets in the lightest possible way. The result is a clincher disc that weighs in at a svelte 1005g (compared to 1175 for the Zipp Super9). The wheel is tubeless compatible and has a wide, modern 19mm inner width to pair with the wider tires and lower pressures that riders are using today with great success.

race acrton images

Inflating a clincher disc is no small feat – usually requiring a crack pipe or, in our case, we prefer a Silca Hiro. To help us out, Specialized included a large valve stem pocket hole that is compatible with up to 80mm valve stems and most pump heads, so both inflation and carrying spare tubes is now a breeze.

The wheel’s asymmetrical shape isn’t equally stiff on each side. When you install and inflate a tire on this wheel, it actually changes the dish of the wheel. Instead of compensating for this by adding additional stiffness plies (layers) on the less stiff side, which would have only added unnecessary weight to the wheel, Specialized designed the wheel slightly off center so it adjusts to its final, centered position with an inflated tire.

Roval 321

The 321 features DT Swiss 240 hub internals, is compatible with all freehub bodies including Shimano, Campagnolo, and SRAM XD/XDR, and it’s also equipped with CeramicSpeed bearings. The rear derailleur clearance works with all current derailleurs/cassettes including CeramicSpeed OSPW systems. For those who prefer disc discs, the disc brake version uses a Center Lock disc, 142x12mm thru-axle only.

Aerodynamics

Being that this is Roval, it should be no surprised that testing was performed in the Specialized Win Tunnel. All wheels were tested in the same test session on a Specialized Shiv TT with a Roval CLX 64 front wheel. All wheels were set up with a Specialized Turbo Cotton 24mm tire at 100psi for each test.  The Lightweight tubular disc is included for comparison, and although it is a tubular, Lightweight does not have a clincher option, and Specialized felt that it was a valuable comparison point. It was tested with a Specialized All-Around 2 24mm tire at 100psi.

Aero graphs are shown as a plot of CdA {m^2] over a range of yaw angles. Each gridline represents 0.001 m^2 change in CdA. Specialized’s formula states that this equates to approximately four seconds saved over 40km regardless of speed.

Our Thoughts

Discs are heavy. So a disc wheel that is 100-200g lighter than its competitors makes us take notice. Combine that with aerodynamics on par or better than its competitors and a super-stiff design and we are definitely looking to try it out. Unfortunately, availability is definitely limited. It will be a few months before we’re able to get a look. There is good news for you, though—retail availability is set for June. So keep your eyes open at your local bike shops. If you find one, let us know! You can tweet us at @AeroGeeksFacebook message us, get us on Instagram, or email us at info@AeroGeeks.com. And also make sure to follow us on social media as well because, as soon as we get one in house, we’ll let you know.

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