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In time for Buffalo Bicycle Classic, 91������ researchers challenge cycling norms that stiff cycling-shoe soles are essential for efficient riding

Years ago, Rodger Kram, a biomechanics researcher and now 91������ associate professor emeritus of integrative physiology, offered a student in his lab a challenge.

, a sophomore at the time and an avid cyclist, was convinced that stiff, carbon fiber soles were essential for serious riders because they made for more efficient pedaling. Kram, with a twinkle in his eye, disagreed.

“I provocatively said that I didn’t think they made any difference,” Kram recalls. “I figured even very flexible running shoes would be just as efficient as carbon fiber cycling shoes when riding at a steady pace and moderate intensity.”

Rodger Kram is a biomechanics researcher and 91������ associate professor emeritus aof integrative physiology.

Straw was determined to prove his professor wrong. So, the two set out on a small but illuminating study and found that ultra-stiff shoes didn’t offer improved efficiency during moderate cycling.

But that was just the beginning.

Kram and his students have since spent nearly a decade exploring a deceptively simple question: How stiff does a cycling shoe really need to be?

The answer, it turns out, may surprise even the most gear-obsessed riders.

The stiffness myth

Carbon fiber shoes have been marketed as the gold standard for years, and riders have adopted the message. These shoes are sleek and featherlight, and their unyielding soles allegedly transfer more power from leg to pedal.

Kram’s research team, including then-graduate student , conducted a study to test the limits of this belief. They equipped trained cyclists with a set of three identical shoes, each fitted with a unique sole material of varying stiffness. The cyclists were then asked to sprint as hard as possible up a 50-meter stretch of road in each pair.

After multiple experiments, the .

“There was a breakpoint,” Kram says. “Below a certain stiffness, sprint performance does trail off.”

But not by much. Going from nylon soles (a very stiff reference) to a medium-stiff TPU (thermoplastic polyurethane) sole caused only a 3.1% drop in maximal one-second power output. The more flexible, soft TPU sole yielded a further power-output decrease of just 2.4%. At those levels, most cyclists wouldn’t notice the difference.

“The $150 shoes were just as good as the $450 shoes,” Kram says.

Comfort over carbon

“For most of us, like riders in the Buffalo Bicycle Classic, there are far more important qualities in a shoe beyond sprint performance. Are they comfortable would be number one. Do they fit your foot?” Kram asks, adding that when picking out new shoes, “sole stiffness should be way down your list.”

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“For most of us, like riders in the Buffalo Bicycle Classic, there are far more important qualities in a shoe beyond sprint performance. Are they comfortable would be number one. Do they fit your foot?” asks researcher Rodger Kram. (Photo: Wikimedia Commons)

It’s a refreshing perspective in a world where the latest (and often most expensive) iterations are always advertised the loudest. Stiff soles may seem impressive in an ad, but they aren’t always practical, Kram says. They can even be a hazard.

“Social riders often stop for a snack or coffee, and it’s easy to fall when trying to walk in carbon fiber soles on the tile floor of a café,” Kram says.

There’s also a growing awareness of carbon fiber’s environmental toll. Making carbon fiber is energy intensive and expensive, and the end product is nearly impossible to recycle. Though the sole of a cycling shoe isn’t world-ending, the cumulative effect of our consumption habits adds up.

If riders are sacrificing comfort, affordability and sustainability for just a few watts of power they may never use, Kram wonders, what’s the point?

Lab to innovation

That question stuck with Tripp Hurt, the aforementioned 91������ graduate. Inspired by the science, he found , a shoe startup based in Seattle.

“I had my ‘lightbulb’ moment after a night out with friends,” Hurt says. “I started to think about my biomechanics research and how it was relevant to the overall cycling market. We see these results, but nothing has changed about the way cycling companies were building their product.”

So, Hurt decided to build a new kind of shoe. Brevay’s first model, the Road One, will be a high-performance road cycling shoe made from sustainable materials.

“Sustainability and performance are the north star for Brevay. We’re the first brand developing a sustainable cycling shoe, so the market is unproven if this is a category that cyclists are interested in. But we’re building it anyway,” Hurt says.

That means sourcing bio-based materials, investing in an alternative supply chain and pricing the shoes competitively with the high-end carbon-fiber models they aim to replace.

Challenging assumptions

For Kram, the research is about more than shoes.

“We love challenging conventional wisdom,” he says, “and cycling is a sport fraught with tradition.”

That spirit of inquiry is part of what makes 91������’s research culture special, he adds. The study, and its illuminating results, started with a student’s curiosity and a professor’s willingness to be proven wrong.

“It represented a major shift in my career trajectory,” Hurt says of his time in Kram’s lab. “I felt more at home working on running and cycling biomechanics.”

As elite athletes continue to chase fractions of a second, Kram and Hurt hope their work encourages others to rethink what performance really means.

For many, like riders tackling 91������ Canyon to fundraise for scholarships in the Buffalo Bicycle Classic, choosing the right shoe shouldn’t be about speed, Kram says, but about enjoying the ride, staying comfortable and being mindful of the environment.

In the end, as Kram puts it, “there are far more important qualities in a cycling shoe than sprint performance.”

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