Leg shaving in cycling is a ritual that's been around for decades. Whether it's to keep the post-ride massage from pulling out your hair or to make wound care easier to deal with after a crash, you can find plenty of answers as to why cyclists go hairless.
What you won't get are cyclists who fess up to the real reason most actually do it—because shaved legs can make you feel faster on the bike, especially when you're suited up in your aero race kit.
But up until recently, there was no evidence to support the it-feels-faster claim.
As an engineer, I was surprised as everyone else when the news broke that wind tunnel data showed that shaving your legs does indeed make you faster on a bike.
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The results of the tests in the Specialized "Wind Tunnel" were astounding. Cyclists saved between 50 to 80 seconds over a 40km/24.8-mile course. This equates to a power savings of 10 to 15 watts—the gold standard for calling a bike modification a "big deal" in the sport of cycling.
Chris Yu, Specialized's own aero expert, put the results in perspective. "That difference is basically like going from a traditional round-tube frame all the way to a Specialized Venge (an aero road frame)."
Among engineers, aerodynamics are usually considered to be a much more important consideration when buying a bicycle than the actual weight. But Yu's comment does reinforce a few important concepts.
The key to saving energy and gaining time on the bike is to understand that the whole is greater than the sum of its parts. That can be rather aggravating when you learn why putting a $3 water bottle on your bike ruins its $5,000 worth of computer-aided aero design. Likewise, the cost of upgrading from an "old school" frame to a new age aero road bike can bite the wallet a bit more than it does from the purchase of a $2 razor.
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Even if you already shave your legs, there may still be time savings to be gained. If you have what the Specialized team calls a high "Chewbacca factor" on your legs, then you probably have it on your forearms, too.
Studies indicate that the surface area of the average person's lower arm is 36 to 41 percent of their lower leg. While the leg and forearm are exposed to the air at different angles during cycling, the Specialized test results suggest that shaving your forearms might be of some advantage. The savings though probably wouldn't achieve the vaunted 10-watt threshold.
The results of the Specialized test weren't the most scientifically executed research in the history of cycling. If you wanted to publish the results in a scientific journal, it would take more documentation and several more test subjects.
In any case, the point appears more or less proven. Research and results are nothing without the "so what?" In this case, Yu gives us a bit of insight—gains on the bike are always relative. Whether it's the "high tech" benefits offered by an aero frame or the "low tech" approach of simply shaving your legs, physics and air molecules never discriminate. It's just another reason to check your gear, prioritize your aero budget, and shave your legs before race day so that you're as fast as you can possibly be.
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