Good news, gentleman cyclists. The next time someone asks why you shave your legs, simply flex your bald calf muscles and say, "Science."
Last week, Specialized Bicycle Components released a video claiming shaved legs are significantly faster than furry ones. How much faster? They provide almost as much of an advantage as switching from a round-tube frame to an aero-style one, says Mark Cote, who does aerodynamics R&D for the California-based manufacturer.
“We were shocked,” says Cote. “The numbers dropped so much it set my bullshit meter off. I had to immediately check the equipment to make sure it was real.”
Specialized opened its “Win Tunnel” in May 2013 as an on-site space to test the aerodynamics of its products—not the aerodynamics of body hair. (As far as we know, Specialized has no plans to move into the shaving market, though we have to say “The Shiv” would be a great name for a carbon-fiber razor.)
But in January, pro triathlete Jesse Thomas showed up for a tunnel testing session. It had been almost a year since his last race and his manscaping habits had gone into 1970s territory. “I only shave before races because Lauren doesn’t like it,” says Thomas, referencing his pro-runner wife Lauren Fleshman. “I don’t know if she actually doesn’t like it or if she’s just saying that to make me feel better because I’m kind of a hairy guy."
Apparently “kind of hairy” is an understatement. The Specialized researchers set up a scale (called the Chewbacca Scale, naturally) to rate the general hairiness of each of the six subjects they tested. On a scale from one to you-can-knit-it-into-a-sweater, Thomas ranked as a nine.
“I was actually semi-embarrassed,” says Thomas. But then he and Cote realized measuring his efficiency pre- and post-shave might be a good PR stunt. They got out a bucket, put on some rockin’ 80s jams and sheared Thomas.
“We’d tested a bunch of stuff earlier that day—kits, wheel, helmets—and the most change I’d gotten was like seven or eight watts from a super aero kit,” says Thomas. “We start up and Mark does 60-second tests—we usually do two—and he just keeps running one then another then another then another. He’s just staring dead-eyed at his computer.”
Cote was seeing a difference in efficiency translating to 79 seconds saved over 40 kilometers—twice what any equipment change had given Thomas during the entire day's worth of testing. That translates to roughly a quarter-of-a-mile-per-hour faster.
“We’d spent three hours in the tunnel and I knew he was consistent,” says Cote, meaning that Thomas was capable of replicating the same form during each test to make sure results weren’t skewed. “We have cameras to double check that, and we checked everything afterwards—none of us believed it.”
Over the next six months, Cote and his colleague Dr. Chris Yu tested five other hairy beasts in the “Win Tunnel.” Average riders saved 70 seconds per 40 kilometers after shaving their legs. To put that in perspective, Specialized’s aero Evade helmet gives an average advantage of 46 seconds over 40 km. Combine shaved legs and an Evade helmet, and you could save upwards of two minutes.
Cote will be the first to admit that the sample size is small and that it isn’t the kind of thing that’s going to end up in a peer-reviewed journal. Still, the results make sense. In 2000, NASA researcher Dr. Rabi Mehta found that a tennis ball’s fuzz affected its flight more than the size or the weight of the ball. In a wind tunnel, he determined that each fuzz filament on a ball added its own bit of drag—which is essentially what your leg hairs do when you ride.
“Shaved legs are just one more part of that speed formula,” says Cote. “It all adds up: the legs, the helmet, the aero frame. And this finally gives our girlfriends and our wives a real reason why we do this.”
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