For riders competing in disciplines where absolute aerodynamic efficiency is critical, the engineering team at HUNT Bike Wheels saw the potential for wider, front and rear-specific rim profiles to provide considerable time savings while offering improved stability in crosswinds. Stability and predictable handling characteristics allow the rider to maintain a low, aerodynamic position on the bike despite changing wind conditions.
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Driven by in-house Computational Fluid Dynamics (CFD) analysis and extensive wind tunnel testing, HUNT has expanded the Aerodynamicist collection to include two deep-section carbon wheelsets to meet the needs of triathlon, time trial and criterium riders. The design approach addressed the differing aerodynamic demands of front and rear wheels as part of the whole system to deliver maximum confidence in handling and exceptional speed. The three resulting wheel designs include two front wheel options with depths of 73mm and 83mm, both paired with an 87mm-deep rear wheel, offering riders the choice between two distinctly different wheelset systems depending on their conditions, preferences, and goals.
Both wheelset offerings provide world-class aerodynamic performance for the rider against the tested competitors whilst delivering stable and predictable handling characteristics. Laced to our new, lighter Sprint SL hubs offering rapid 7.5-degree engagement, these wheelsets are built for race day. HUNT has published a full research white paper summarizing the results of the two-year-long design, development, prototyping, testing and validation process. Read Less
7387 AERODYNAMICIST CARBON DISC
The HUNT 7387 Aerodynamicist Carbon Disc minimizes steering forces, providing exceptionally stable and predictable ride characteristics, while offering extremely low aerodynamic drag.
Aerodynamicist rim profile, exclusively engineered and wind tunnel tested by HUNT's in-house engineering team, featuring a hooked and ETRTO-compliant tubeless-ready rim, designed for tubeless tyre compatibility.
Full Wind Tunnel Tests
INTRODUCTION AND PROCESS
HUNT set out to create two wheelset systems for riders seeking the utmost in aerodynamics for time trial, triathlon and criterium racing, each set with a different front wheel depth, allowing riders to choose the best option for their riding. After two years of CFD modeling, prototyping, wind tunnel testing, and rider testing, HUNT created an 87mm deep rear rim profile maximized for the aerodynamic demands at the rear of the bike and designed to provide optimal lateral responsiveness and efficient power transfer. The two front wheel options offer riders category-leading aerodynamics and crosswind stability at different depths, depending on their riding conditions, preferences, and goals.
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The widespread adoption of disc brakes in all formats of modern racing has offered the opportunity to transform rim profile development without the dimensional constraints of rim brake calipers, allowing for wider, aerodynamically optimized rims shapes. On top of the aerodynamic possibilities, riders also benefit from wider tyres and lower pressures, known to reduce rolling resistance and road vibration while improving grip. Time trials, triathlons, and criteriums are specific disciplines in which the high average speeds and typically flat courses offer the opportunity to generate significant aerodynamic benefits for the rider through deep rim profiles. However, the high speeds and common crosswinds require those deep wheels to be stable and predictable, so that the rider can maintain a low, aerodynamic position on the bike regardless of conditions. These demands (fast and stable) are both met through wider profiles.
CFD PROCESS
In recent years, HUNT has invested in developing its Research and Development capabilities to deliver science and engineering-led, high-performance wheels to their riders. One key focus has been to build in-house expertise in using Computational Fluid Dynamics (CFD) modelling techniques in the aerodynamic design of performance bicycle wheels.
CFD is the analysis of fluid flow around an object using numerical methods and a computational model to replicate the desired conditions, such as a bicycle wheel in a wind tunnel, and assess the aerodynamic performance. It is a development tool that accelerates the engineering process and allows us to explore new ideas and iterations at a rapid pace, but it is not a replacement for wind tunnel testing, which combined with real-world rider testing, provides the final validation of product performance. Traditionally, aerodynamic profile development has been conducted in the Wind Tunnel, which involves manufacturing several prototypes to test theories and profiles. This often means executing a wind tunnel test session without clear prediction of the outcomes, which can then necessitate the time and investment-intensive process of repeated prototyping and testing to identify the optimal solution.
PROFILE DEVELOPMENTS
The HUNT engineering team selected a depth of 73mm for shallowest front rim profile, chosen to minimize the effects of side forces from crosswinds whilst maximizing aerodynamic efficiency in a straight line. The validated wind tunnel performance of the 60 Limitless Aero Disc served as the benchmark and starting point for the 73mm profile. Feedback from HUNT-supported WorldTour riders (2021 Team Qhubeka Assos) suggested that the extra wide rim profile of the 60 Limitless Aero Disc resulted in an ultra-fast wheelset that handled cross winds and side forces like a much shallower wheel, an attribute that would be extremely valuable in an even deeper format.
The initial design concept for the deeper 83mm front rim profile began more traditionally in terms of width and shape. However, the CFD and wind tunnel-led development process quickly identified the potential for a wider shape to improve performance, even at the 83mm depth. A wider profile was modelled using CFD, then prototyped for further testing.
WHY WE CREATED FRONT AND REAR SPECIFIC RIM SHAPES:
Due to the generally laminar (constantly attached) nature of airflow, an object immediately behind another object will be subjected to disordered airflow of different speeds and directions, and therefore must be designed to reduce drag in those disordered airflow conditions. Applying this to cycling, and in particular, wheels, front and rear wheels encounter different airflow conditions and therefore have unique aerodynamic roles to play in the system. The HUNT engineering team has purposefully designed the front and rear rims in this system for their specific role, creating an optimal combination of drag reduction, crosswind stability, and low weight.
THE RESULTS
Figure 14 – Hunt 7387 pre-production Wind Tunnel Test Drag and Steering Moment Graphs with Schwalbe Pro One 25mm Tyre
As shown in the graphs, the HUNT 7387 Aerodynamicist produce exceptionally low drag values when compared to numerous leading relevant competitors with both 25mm and 28mm tyres (see white paper for full tested competitive set). The DT Swiss Dicut 80F / 80R produced the lowest aerodynamic drag from the competitor tested and became the benchmark competitor for further testing.
The HUNT 7387 Aerodynamicist Carbon Disc wheelset, our shallower front wheel offering, was designed to maximize aerodynamic benefit with minimal steering moment magnitude. The final tests concluded that the HUNT 7387 Aerodynamicist Carbon Disc wheelset provides very low steering moment given its depth, easily outperforming most industry leading competitors in both stability and minimising aerodynamic drag, performing only 0.35W slower than the deeper 8387 offering in the same conditions whilst minimising steering forces. The HUNT 7387 Aerodynamicist delivered results within 0.52W of highest performing DT Swiss Dicut 80mm, when paired with both 25 and 28mm tyres.
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