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New wind-tunnel tests find surprising gains in cycling efficiency from leg-shaving

13K views 78 replies 31 participants last post by  Alex_Simmons/RST 
#1 ·
The curious case of the cyclist?s unshaven legs - The Globe and Mail

Is shaving your legs a matter of fashion or function for cyclists? When Oregon-based triathlete Jesse Thomas forgot to shave before a wind-tunnel testing session earlier this year, he realized that he had a rare opportunity for a before-and-after test to find out.

“It honestly was a total joke,” he says. “None of us expected [shaving] to make much of a difference.”

Instead, the reduction in aerodynamic drag was so significant that even the researchers running the test didn’t initially believe it.
...
The tests showed that shaving his legs reduced Thomas’s drag by about 7 per cent, allowing him to exert 15 watts less power and still go at the same speed. In theory, that translates to a 79-second advantage over a 40-kilometre time trial that takes about one hour.

In comparison, the other fancy components and techniques that Thomas had flown to California to test seemed relatively minor. A new helmet saved him 2 or 3 watts, his unorthodox “praying mantis” arm position saved 5 watts, and a new long-sleeved racing suit saved another 8 watts.
 
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#4 · (Edited)
I thought the opposite results have been shown numerous times.
It was pointed out in the article that no-one has really done any follow up research on the basis of the initial (flawed) results

from TFA

The aerodynamic benefits were generally considered a minor side-effect, more of a placebo than anything else.

The most widely cited test was a 1987 study for Bicycling magazine by engineering professor Chester Kyle, one of the pioneers of cycling aerodynamics. He found that leg-shaving reduced drag by 0.6 per cent, enough to save about 5 seconds over the course of one hour at the brisk speed of 37 kilometres per hour. At slower speeds, the savings would be less.

Given that meagre benefit, along with the fact that wind-tunnel testing generally costs at least $500 per hour, it’s not surprising that no one felt the need for further leg-hair testing.
...
In this case, Cote contacted Kyle, the author of the earlier study, to ask if he had any ideas about the discrepancy between the two results. It turned out that the 1987 test involved a fake lower leg in a miniature wind tunnel with or without hair glued onto it – hardly a definitive test, and yet it was enough to persuade most people not to bother with further tests for the next three decades.

It really should be fairly simple to test.
You mean like they did in the article?

again from TFA

The Specialized aerodynamicists in charge of the wind tunnel, Mark Cote and Chris Yu, were so surprised that they tested five more cyclists before they would let Thomas publicly reveal the findings. The results were consistent: All of them saved between 50 and 82 seconds over 40 kilometres.
 
#9 ·
I have been on the fence on leg shaving, i.e., balancing the cyclist
thing with the horror of my brothers seeing my shaved legs (they
already think I'm somewhat of a nut case cyclist with my shaved head
in summer). Oh well, time to join the party....
 
#18 · (Edited)
It seems like the results would be very individual and based on a few things:

1. How hairy are you?
2. How long are your legs?
3. How long are your shorts?

Take a really hairy long legged dude with short cycling shorts and have him shave his legs and compare that to a shorter legged, less hairy rider who typically wears shorts that comes to his knees and the results might be a bit different.

edited to add the "s" to "leg"
 
#19 ·
It seems like the results would be very individual and based on a few things:

1. How hairy are you?
2. How long are your leg?
3. How long are your shorts?

Take a really hairy long legged dude with short cycling shorts and have him shave his legs and compare that to a shorter legged, less hairy rider who typically wears shorts that comes to his knees and the results might be a bit different.
Interesting analysis. So is wearing tights "manlier than shaving your legs??
 
#24 · (Edited)
Even if shaving is rigorously tested and proven to confer a slight aero advantage, is this info really going to change anybody's mind who isn't shaving yet to start?

Seems to me the whole aero arguement was just a wink-wink :smilewinkgrin: reason for doing it anyways- kind of like the "less painfull massage" theory (like any Joe sixpack has a personal masseuse available after every ride).
 
#32 ·
It doesn't even matter.

If you're a racer type you're probably gonna shave your legs whether there's a benefit or not.

If your not a racer type, you may or may not shave your legs, and aerodynamics probably isn't even an issue.

The whole discussion ain't much different than the helmet debate or the stop sign argument or any of the other things that we can't agree on here.

I do it my way and you do it your way and ain't neither one of us gonna talk the other into doing it the other way.

That's how families are, they argue about stuff.
 
#44 ·
That would be even hotter if you were a girl!
 
#47 ·
i may have anecdotal evidence to back this up.
there is an 11 mile loop that i periodically time myself on.
over last season and this my time has steadily dropped over the months.
i timed myself in late june of this year. then it wasn't until mid/late august that i timed myself again.
in june my hairy-legged time was 36:30 for the 11 mile loop
then i shaved... well, i actually epilated my legs
did the timed loop again and came in with a 35:13 time
come to think of it, maybe it was the fact that i was about 6.5-7 lbs lighter?
 
#48 ·
i may have anecdotal evidence to back this up.
there is an 11 mile loop that i periodically time myself on.
over last season and this my time has steadily dropped over the months.
i timed myself in late june of this year. then it wasn't until mid/late august that i timed myself again.
in june my hairy-legged time was 36:30 for the 11 mile loop
then i shaved... well, i actually epilated my legs
did the timed loop again and came in with a 35:13 time
come to think of it, maybe it was the fact that i was about 6.5-7 lbs lighter?
Man, how hairy were your legs?
 
#52 ·
The new top secret dimpled aero Speedskating suits revealed for Team USA at Sochi were a complete fail. We had skaters posting significant drop offs and missing medal opportunities. Some skaters dropped the new uniform and went back to the old ones they trained in. There's something to this aero thing, but I'll say, the new suits were wind tunnel tested.

US speedskating skinsuits under scrutiny as team struggles in Sochi | Fox News

granted, coaching problems, team chaos... But actual previous skating results across that season were excellent?
 
#55 ·
With all my cycling crash scars I'm rough-textured too... I never believe anything tested in a wind tunnel because invariably the test is done by a company who has a vested interest in the results.

The company can therefore a) omit results that are contrary to their business model, and more importantly b) tailor the testing conditions to favor their product. The latter accounts for significant claims that are true, but encountered in 0.1% of actual cycling conditions.
 
#56 ·
The company can therefore a) omit results that are contrary to their business model, and more importantly b) tailor the testing conditions to favor their product. The latter accounts for significant claims that are true, but encountered in 0.1% of actual cycling conditions.
Plus, to be fair, those tests are really, really hard to do in a way that gives accurate results. So, while I agree somewhat with your skepticism as well founded, I would modify it to say that I don't trust any results that have not been reproduced by independent tests. This, of course, is doubly true when the results are so far off from both the results of others, and expectations from theory.

I remember overseeing work trying to reproduce wind tunnel test results (for a very different, but similarly difficult problem) by one of the best experimental labs in the world (I'll stick to both my and their privacy, but it's at one of the top-ten universities in our country), directed by a good friend of mine who is likewise among the very top, worldwide, in his field. Long story short, it turned out his measurements were completely wrong, and we don't even fully understand yet why they were so far off. So, if I'm looking at implausible results obtained by some dudes working for Specialized, and obtained in a new and unproven wind tunnel, excuse me for being more than a little skeptical.

As an aside, if you add up all the Watts that various measures (frames, wheels, helmets, aero bars, shaving, ceramic bearings, etc., etc.) are supposed to save you, you'll find that your bicycle should move by itself, with zero power input from the rider. Maybe something's a little off here, watcha think?
 
#71 ·
I think you'd need to perm it... the hair that is.... Everywhere!

Maybe my back hair can lower the drag behind my head?
 
#79 ·
If aero would be of any real importance, Pros would gear up in full body sharkskin swimsuits or have their shins remodelled in wing shape.
If such things were permitted by the regulations, I'm sure they would do all sorts of things.

You may laugh, or are simply ignorant of such things, but on body fairings and speciality materials have been used in cycle racing for a long time, but most are prohibited in UCI events. Indeed Tony Martin has used such things that are or bordered on non-permitted with added shapes, "winged" skin suits, and of course much work went into BC's skinsuits with fabric textures and seam placement used as air flow trips on so on.

Rather than that, I'd ask what Eddy Merckx would have done.
Eddy would go for every advantage available to him under the regulations (and probably a few that weren't), just like he did in his day.
 
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