So you’re looking to buy a new pair of cycling shoes for the upcoming season and have a few questions.
Many aspects of shoes, say colors, choice of either leather or synthetic material upper, or the type of tightening method (Boa-dial, ratchet strap, Velcro, or laces), are pretty easy to decide on. But with most manufacturers hyping the benefits of shoe stiffness, the decision-making process gets a little more difficult.
Just like a bike, cycling shoes can be soft and compliant or stiff with better power transfer, depending on the materials used.
“We have 26 bones, as well as a bunch of muscles and tendons, in our feet, which all do fantastic things for us while walking – adapting to uneven ground to prevent injury, improve traction, and making us efficient walkers and runners,” said Stephen Quay, footwear guru for Specialized. “But once you connect a person to a bike, this adaptation no longer needs to happen. In fact, that foot collapse represents an inefficiency; your full power isn’t being transferred to the pedals. Our objective is to transform the foot into a rigid lever, turning it into a point of adaptation between the hip/knee extension and the crank arm.”
Most entry-level shoes use a nylon footplate; as the price point goes up, so does the quality – and hardness – of materials. Mid-level shoes often use fiberglass or a mix of the two materials to create the footplate, while carbon fiber is used in many of the more expensive shoes.
“The more layers, the thicker the carbon, which means increased rigidity,” said Diana Pickler, Footwear Product Manager for Pearl Izumi. “Another way to increase strength in carbon is to change the angles of the fibers to overlap in a crisscross-like pattern. The materials will be heated, then put in a compression mold to fuse the layers and create the desired shape.”
Specialized creates additional stiffness with its torsion-box construction, Quay claims. Inserting a lightweight spacer between the sole’s two carbon walls creates, in essence, a carbon box that’s stiffer than standard layering.
Each manufacturer has its own stiffness index; Scott has a standard 1-10 scale with its Road RC shoes at the top, while both Shimano and Specialized go beyond even Spinal Tap, rating its shoes up to 12 and 13, respectively. The lack of an industry-wide standard has led to some shenanigans, Quay joked.
“There have been a few brands that (we believe) have copied our stiffness index and seem to always be a point stiffer than us at any given price point,” Quay said. “Nothing fishy there at all.”
So why not go with the hardest, stiffest mid/outsole for every shoe? Price, comfort, and usability. The experts interviewed generally agree that competitive or serious recreational cyclists should aim for the stiffest shoe their budget will allow, but more casual riders will benefit from a less efficient, but more comfortable, shoe.
There are some exceptions however. Some mountain bikers spend more time off the bike, hiking over debris or up an impossibly steep section of singletrack, so more flex is crucial. Each manufacturer has their own way to balance stiffness and flex, says Gianni Franco, Research and Development Manager at Northwave. Pearl Izumi uses a shorter, three-quarter sized shank that allows flex in the toe and rear without compromising the power, as well as rugged, lugged rubber outsole for traction.
Surprisingly, the desired stiffness will vary—not only based on your preferred cycling discipline—but also on your type of steed, says Pickler. The Sidi Dominator’s softer plate provides less harsh trail feedback for riders on rigid XC-type bikes, while many full-suspension riders might gravitate toward a stiffer shoe, like the Shimano S-Phyre.
Can engineers create a shoe that’s too stiff? That’s definitely up for debate, but Quay admits there are definitely diminishing returns.
“Potentially, there’s a point when you’re already [effectively operating] at 100 percent efficiency,” Quay said. “At that point, adding more stiffness would seem useless and would just result in increased weight and cost.”
So what’s the best? Can you have a super-stiff sole that’s still very comfortable? Yes, but it requires another investment.
“A good insole or sockliner is key to the balance of comfort,” Pickler said. “Having a quality insole with proper arch support and forefoot cushion can help combat the discomfort that may accompany a stiff plate, especially on longer rides.”
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