AX-Lightness

Ultra 28C Extralite Hub Clincher Wheelset

AX-Lightness is a one of those rare, boutique operations that operate on the fringe of the mass-produced cycling industry. It brings unrivaled Bavarian meticulousness to bear on each individual piece it manufactures, and the entire process — from conceptualization to construction — takes place under the same roof in Creußen, Germany. The Ultra 28C wheels, served up here with Extralite's hubs, are lightweight and safe with all the efficiency you'd expect from carbon wheels and a healthy dose of secure, confident braking that you might not.

The rims' shape is informed by the same fluid dynamic considerations the German Manufacturer pours into its motor sport designs. The rims swell to 26 millimeters at their widest external point and a generous 18 millimeters internally. This means you can run a lower tire pressure for a more comfortable ride, all while decreasing rolling resistance and increasing cornering confidence. After all, what good is a fast, aerodynamic profile if you have to slow down to tip-toe through corners?

Aerodynamics also typically hurt when a crosswind gets ahold of your rim, but the Ultra 28Cs terminate in a blunt, round shape rather than a point. This keeps unruly laminar air in check as it travels across the rim's surface, eliminating drag-inducing pockets of dead air in the rim's wake. It also refuses crosswinds any purchase, so handling remains consistent and predictable under changing conditions.

While that combination of aerodynamics and handling in crosswinds eliminates the typical drawbacks of deep rims, stiffness and weight are still important aspects of any racing wheels. AX uses a carbon weave for the Ultra rims because, unlike the ubiquitous unidirectional fibers of late, a woven fabric has load bearing properties that recommend it for the dynamic load angles experienced by a wheel's rim throughout its rotation. This means efficient power transfer and torsional stiffness can be achieved with less material, which in turn results in less weight.

The Ultra 28Cs feature the universal construction technology that defines AX's wheels, including the Seamless Brake Surface (SBS). SBS uses high-pressure autoclaves to combine the wheels' layers with gas, eliminating any imperfections down to the smallest edge for a one-piece brake surface that's both seamless and virtually free of imperfections. It may look like a typical, mass-production rim, but the Ultra rim is nearly perfect on a microscopic scale, so there's no shuddering while braking during descents. After curing, the wheels are tempered, which realigns the resin crystals to drastically increase the braking temperatures that they can withstand before the carbon softens and deforms.

The wheels' reliability is also boosted by Spoke Reinforcement Technology, which creates the spoke holes during the manufacturing process itself. There is no post-production drilling once the rims come out of the autoclave, so there's no additional structural weakness. As a result, the Ultra 28C can bear five tons of nipple pressure, which AX takes advantage of by tensioning the spokes to 1300 N.

While the rims are purely the result of meticulous German engineering, the hubs come from Italy. AX-Lightness uses Extralite's Ultra Front SP and Cyber Rear SP hubs, which maintain the focus on lightweight climbing. The oversized flanges are specially treated to self-align under spoke tension so they better handle that high tensioning stress. They also increase the spokes' stiffness, and therefore the lateral stiffness of the wheel. An oversized axle results in even less watt-losing flex while gliding up gradients in the mid-teens, and the over-sized bearings complement the rims' aggressive climbing profile by reducing the amount of mechanical friction you experience during punchy attacks.