Making up about 50% of your total race time, the bike portion of a triathlon is where equipment choices can make the difference between first and fifth. No other equipment choice will save you more time than a disc wheel. While traditionally-shaped disc wheels are faster than their spoked counterparts, the 321 disc turns conventional design on its head, creating the fastest wheel available.
Disc wheels often fall into two categories - a completely flat shape, with structure coming from carbon fibre and a honeycomb-foam filling, or a spoked wheel that's been faired with a carbon fibre cover. To break traditions, the 321 uses a single layer of 1k carbon fibre on each side of the wheel, and it all comes together at the brake track bridge. This kind of carbon fibre is rarely used in bicycle components due to its high manufacturing cost, but it offers a bevy of performance benefits. This coveted carbon is much lighter than other layups, like 3k and 12k, and it can only be laid by the most skilled of carbon fibre craftsmen. It's complicated, but the payout is worth it, as it delivers a supple ride and one of the lightest disc wheels available. This means that it'll spin-up quickly and reduce fatigue over the long haul.
It's long been thought that efficient power transfer and high stiffness are directly correlated, but through extensive field testing, Specialized have determined that this isn't the case. The initial disc was so stiff that, under power, it wouldn't flex with the frame and this caused brake rub. This wrongly creates the perception of a flexy wheel, when really, the wheel is actually too stiff. To solve the brake rub problem, Specialized first designed the optimal aero shape and then worked on internal stiffness targets to fit within what they consider to be a desirable frame stiffness.
While light overall weight was a development priority, the focus was aerodynamics. Through hours of Computational Fluid Dynamics (CFD) and testing in the Win Tunnel, a new-to-category shape was developed that's optimised to work with a tyre for on-bike airflow. This translates to an all-carbon disc wheel that, on the non-drive-side, has a shape that's as aerodynamic as our current understanding allows, and a drive-side shape that's as aerodynamic as the wheel-dish and derailleur clearance will allow for.
To save every possible watt, CeramicSpeed bearings and DT Swiss 240 hub internals have been added into the hub. Each 321 Disc wheel is also 2Bliss-Ready out of the box and comes with a padded wheel bag, quick-release, tubeless valve, and SwissStop Black Prince brake pads.
Designed for the most uncompromising athletes in the world, with engineering to match, the 321 Disc is the world's most advanced disc wheel for your race against the clock.