Zipp

Sub-9 Carbon Road Disc Wheel - Tubular

When your accolades include some of the fastest Ironman-distance bike splits ever recorded, a Yellow jersey at the Tour, and a pair of Ironman 70.3 World Championships, you know that you're on the right track with your wheel design. Such is the case with Zipp's Sub-9 Rear Tubular Disc, as it continually proves itself to be one of the fastest disc wheels on the planet.

Unlike traditional disc wheels, the profile of the Sub-9 features a toroidal bulge that's similar to Zipp's spoked carbon wheels. Because of this design, Zipp was able to produce the first wheel with forward lift, or "negative-drag." Zipp built the wheel with this design for several reasons -- the bulge around the edge of the disc works to control airflow at the wheel's leading and trailing edges, and it also provides better vertical compliance compared to a standard disc shape. So, in addition to boosting aerodynamics, the Sub-9's slight amount of vertical 'give' keeps the wheel glued to the tarmac while cornering, and it provides a comfortable ride for those long hours in the saddle.

The Sub-9 still features the dimpling pattern that's found on the 900 and the Firecrest models, which effectively smooths air flow in order to minimize drag. Zipp calls this its Aerodynamic Boundary Layer Control (ABLC). Essentially, this is a treatment to the carbon fiber, where the surface is embossed with over 4900 golf ball-like dimples in five different sizes. As a result, along the curved rim section, the dimples work to create a slight turbulence directly above the rim surface. This creates an artificial boundary layer that forces the laminar boundary layer towards the forward part of the rim in order to become turbulent. This process enables airflow to remain attached over more of the rim for a longer period of time, providing a lower level of integrated drag. The drag that ABLC creates is called skin friction drag. And although it's greatly increased, pressure drag (which is ten times higher than skin friction) is accordingly decreased. So, you experience less drag at effective wind angles between 10 and 20 degrees.

The hub used is Zipp's durable 188 model, with internals manufactured using Zipp's high-voltage, Wire EDM technology. This specialized manufacturing process, usually reserved for avionics and Formula One gearboxes, lets Zipp machine 50% harder materials at tolerances 20 times greater than standard machining and heat treating. The result is a sub-200g hub that's able to withstand the torque of a four-cylinder car engine.

The Zipp Sub-9 Rear Tubular Disc Wheel, which weighs in around 998 grams, is an ideal triathlon or time trial setup when paired with the 808 or 404 Firecrest. It's available with either Black or White labels and a Shimano/SRAM- or Campagnolo-compatible freehub body. The wheel comes with Zipp's new Tangente Platinum Pro Evo Brake Pads, as well. Please note that Zipp does not recommend deviating from these pads, and that doing so may result in a void of your warranty.