Real World Aerodynamic & Rolling Resistance Testing with Hannah Shell.

Over the past few years, competitive gravel racing has seen a seismic shift. What was once a realm of self-supported grit is now a discipline shaped by aerodynamic refinement and marginal gains; mirroring what road, time trial, and triathlon athletes have pursued for decades.

While gravel bikes differ in key ways from time trials, tire size is the most obvious: riders are now pushing into wider casings and even lightweight MTB tires in search of better rolling resistance. Hannah Shell, a consistent contender at the sharp end of the gravel scene, recently began working with aerodynamicist Marc Graveline to fine-tune her setup for marquee events like Unbound Gravel - a 200-mile epic where every watt counts. Having already tested a wide 2.1" MTB tire setup on her Cervélo Áspero with a FOX 32 suspension fork, Hannah set out to validate and optimize her entire system ahead of race day.

We caught up with Hannah and Marc outside Boulder, Colorado, for a behind-the-scenes look at real-world aero and rolling resistance testing. Building on early sessions in Arizona during Hannah’s winter training block, the duo honed in on reducing rolling resistance without sacrificing performance or ride feel.

Marc’s approach is rooted in data. His sensor system collects over 120 distinct inputs - air speed, barometric pressure, road gradient, vibration, steering input, and more - sampling up to 600 times per second. Combined with GPS, power, and speed metrics, the data allows for deep real-time and post-ride analysis. The goal: lower Hannah’s coefficient of aerodynamic drag (CdA) and reduce watts lost to suspension and rolling inefficiencies.

Initial sessions focused on aero testing, comparing riding positions, hydration systems, and storage solutions. While clothing and helmet choice weren’t the priority this time, they remain part of Marc’s wider toolkit. The focus soon shifted to rolling resistance, where Hannah tested Pirelli’s entire range of gravel and mtb tires, and various wheel combinations. The team also examined how different forks (suspension vs. rigid) and fork tuning impacted rolling efficiency. But the process wasn’t just about chasing the lowest numbers—it was about understanding trade-offs. A setup that saves watts might also compromise handling or acceleration during key race moments. That’s where the rider’s insight becomes essential, and Marc’s data-driven “what-if” simulations help guide those decisions.

After months of testing and refinement, Hannah finalised a race-day setup built for speed and stability. She returned to the Cervélo Áspero, fitted with the FOX 32 Step-Cast fork to tame Unbound’s relentless terrain. For wheels, she selected the HUNT 40 Limitless Gravel Aero - proven in testing to deliver aerodynamic performance with confidence-inspiring handling. Tire choice was a deliberate mismatch: a 45mm Pirelli Cinturato™ Gravel M up front for grip and compliance, with a 40mm rear for faster rolling. Every component was selected not just for raw speed, but for how it served Hannah on gravel’s biggest stage.

Hannah rides:

HUNT Proven Carbon Enduro H_Core MTB 29 Wheelset

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