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 and 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 Roval 321 Disc for disc brakes turns conventional design on its head creating the fastest wheel on the planet. 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. In our quest 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 pay-out is worth it as it delivers a supple ride and one of the lightest disc wheels available. And in the real world this means that it'll spin-up quickly and reduce fatigue over the length of the course. Stiffness is often the “hot-topic” in the disc wheel world but we think it’s an interesting conversation. It's long been thought that efficient power transfer and high stiffness are directly correlated but through extensive field-testing we've determined that this isn't the case at all. In fact our 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. In order to solve the brake rub problem we first designed our optimal aero shape and then worked on our internal stiffness targets to fit within what we consider to be a desirable frame stiffness. And while light overall weight was a development priority our focus was aerodynamics. Through hours of Computational Fluid Dynamics CFD and testing in the Win Tunnel we developed a never-before-seen shape that's optimized to work with a tire for on-bike airflow. What this translates to is 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 we've also added CeramicSpeed bearings and DT Swiss 240 hub internals into our hub. Each 321 Disc wheel is also 2Bliss Ready right out of the box and comes with a padded wheel bag quick-release and tubeless valve stem. 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. Rim Type: Full carbon clincher 2Bliss Ready Rim Material: Carbon Braking Surface: Disc brake only Rim Depth: Solid Disc Rim Width: 19mm internal 27.3mm external at brake track Rear Hub: Roval Disc 142x12mm CeramicSpeed bearings DT Swiss 240 internals 11-speed Assembly Method: Handmade Extras: Roval padded wheel bag Roval tubeless valve Roval valve pocket covers Weight: 1015g All Roval Wheels are covered by Specialized's Lifetime Warranty which covers the wheels against manufacturing defects and imperfections. All Roval Wheels are also covered under Specialized's **it Happens No Fault Crash Replacement Warranty for 2 years. Learn more about Specialized Warranty here