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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

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Old 06-28-14, 01:07 PM   #1
wphamilton
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Waving, drag revealed!

It comes up with such frequency, and is debated with so much passion, that it may be one of the most important questions in the sport of cycling, yet no one has really examined it scientifically. Until now.

The roadie in full regalia, his steely gaze is focused and intent, you give a wave and you're ignored. What's up with that? Would it really hurt him to wave? That's usually a rhetorical question but I set out to find an answer. What does it cost him to wave?

So I took my road bike to a local hill to perform some coast-down tests while simulating a roadie in training. I selected a hill with a relatively gentle grade so that speeds would be similar. In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position. I wanted to make the simulation as real as possible so I wore an actual jersey, tight, and spandex cycling shorts. Helmet, sunglasses. All tests were with hands on the hoods (since careful observation has indicated that training roadies ride on the hoods, or with the same back angle while in the drops).

This is the test rig: although it's Fredded up it is, as you can see, a road bike with standard road bike geometry, normal saddle to bar drop, 700x25c tires.

To complete the simulation I strapped on a HR monitor and also turned on Strava, as if I were doing hill repeats. For you doubters out there Bike Ride Profile | Coast-down test repeats near Alpharetta | Times and Records | Strava although I didn't use Strava data since my flight recorder box is more accurate. I did three tests coasting, three waving, with no pedaling at any time. Except uphill of course. I started each test at precisely the same point in the road, with the magnet positioned 1/8th of a wheel behind the sensor.

I threw the second waving run out because passing traffic distorted the data. The final repeat in Strava was not a test run - I just did it because just coasting is pretty boring. Here is the result:

The vertical axis is miles per hour, the horizontal is units traveled (unit representing approximately 7 feet, one wheel revolution)

It's pretty clear that waving costs a significant amount of speed, presumably by adding drag. If we need a number, how much drag, here is a real general estimate. Assuming that the highest speed is the terminal velocity for that grade and object (I haven't proven that, but I've been up and down that hill a lot and it is or is close to) then the drag force is equal to the force of gravity. The force of gravity is the same for both roadie and waving, and therefore the ratio of CdxA (Coefficient of drag times area) is the inverse ratio of squared velocities. From the basic drag equation.

In this case, that comes to about 12% greater drag created by waving. So there you have it: drag is increased by 12% when he waves.
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Last edited by wphamilton; 06-28-14 at 01:30 PM.
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Old 06-28-14, 01:15 PM   #2
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"In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position."

Good information, but who waves the whole time they are riding ?
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Old 06-28-14, 01:16 PM   #3
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Nice, but I'm more of a Fred than roadie, so what would I know.
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Old 06-28-14, 01:19 PM   #4
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"In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position."

Good information, but who waves the whole time they are riding ?
No one does, but that's how you test things. Keep the testing variable constant throughout the test duration.

BTW, I felt like a lunatic waving my arm around while coasting down the hill at 26 mph.
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Old 06-28-14, 01:24 PM   #5
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BTW, I felt like a lunatic waving my arm around while coasting down the hill at 26 mph.
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Old 06-28-14, 01:24 PM   #6
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Entertaining experiment!

I lived in Charlotte for 2 years. In my first week there, I learned that waving was a thing. I liked it, people made you feel welcome. I moved back to SoCal and tried waving at people. They just look at me like I am crazy LOL

I wave anyway even if they don't wave back
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Old 06-28-14, 01:49 PM   #7
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What if instead of waving with your whole hand, you wave with only one finger?
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Old 06-28-14, 01:59 PM   #8
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Conclusion: Waving is a drag.
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Old 06-28-14, 02:47 PM   #9
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Simple entertainment for simple......

P.S Don't forget to factor in the rotation of the Earth and the gravitational pull of the Moon.
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Old 06-28-14, 02:50 PM   #10
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I wave with a snarl

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Old 06-28-14, 02:58 PM   #11
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What if instead of waving with your whole hand, you wave with only one finger?
I can't say about drag, but has been known to cause a major drop in approval ratings...

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Old 06-28-14, 03:12 PM   #12
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I wave with a snarl

And well you should, knowing now that it increases your drag by 12%!

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Simple entertainment for simple.....P.S Don't forget to factor in the rotation of the Earth and the gravitational pull of the Moon.
Possibly the most important question of the sport judging by the number of threads on the subject. These results are not only significant, they are historic even if I do have to say so myself.

Centripetal force at the equator is approximately 1/289 of the force of gravity. Since the difference in velocities between the two conditions (traveling counter rotation) is approximately .0014 that of the Earth's rotation, and since the centrifugal force varies with the square of rotational velocity, the difference in force is 2 times ten to the minus 6 power, corresponding therefore to about 7 time 10 to the minus 9 power fractional of g, and thus disregarded as insignificant.

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Old 06-28-14, 03:16 PM   #13
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And here I thought this is where the thread was going.......

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Old 06-28-14, 03:17 PM   #14
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And here I thought this is where the thread was going.......

I'll leave that test to the more adventurous, or confused as the case may be.
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Old 06-28-14, 04:03 PM   #15
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This might be the most ridiculously awesome thing I've seen on BF.
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Old 06-28-14, 04:09 PM   #16
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:wave:
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Old 06-28-14, 04:43 PM   #17
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Old 06-28-14, 05:11 PM   #18
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Originally Posted by wphamilton View Post
It comes up with such frequency, and is debated with so much passion, that it may be one of the most important questions in the sport of cycling, yet no one has really examined it scientifically. Until now.

The roadie in full regalia, his steely gaze is focused and intent, you give a wave and you're ignored. What's up with that? Would it really hurt him to wave? That's usually a rhetorical question but I set out to find an answer. What does it cost him to wave?

So I took my road bike to a local hill to perform some coast-down tests while simulating a roadie in training. I selected a hill with a relatively gentle grade so that speeds would be similar. In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position. I wanted to make the simulation as real as possible so I wore an actual jersey, tight, and spandex cycling shorts. Helmet, sunglasses. All tests were with hands on the hoods (since careful observation has indicated that training roadies ride on the hoods, or with the same back angle while in the drops).

This is the test rig: although it's Fredded up it is, as you can see, a road bike with standard road bike geometry, normal saddle to bar drop, 700x25c tires.

To complete the simulation I strapped on a HR monitor and also turned on Strava, as if I were doing hill repeats. For you doubters out there Bike Ride Profile | Coast-down test repeats near Alpharetta | Times and Records | Strava although I didn't use Strava data since my flight recorder box is more accurate. I did three tests coasting, three waving, with no pedaling at any time. Except uphill of course. I started each test at precisely the same point in the road, with the magnet positioned 1/8th of a wheel behind the sensor.

I threw the second waving run out because passing traffic distorted the data. The final repeat in Strava was not a test run - I just did it because just coasting is pretty boring. Here is the result:

The vertical axis is miles per hour, the horizontal is units traveled (unit representing approximately 7 feet, one wheel revolution)

It's pretty clear that waving costs a significant amount of speed, presumably by adding drag. If we need a number, how much drag, here is a real general estimate. Assuming that the highest speed is the terminal velocity for that grade and object (I haven't proven that, but I've been up and down that hill a lot and it is or is close to) then the drag force is equal to the force of gravity. The force of gravity is the same for both roadie and waving, and therefore the ratio of CdxA (Coefficient of drag times area) is the inverse ratio of squared velocities. From the basic drag equation.

In this case, that comes to about 12% greater drag created by waving. So there you have it: drag is increased by 12% when he waves.
I'm sensing a Nobel prize in physics.
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Old 06-28-14, 05:16 PM   #19
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Can we look for your full paper in International Journal of Aerodynamics (IJAD) - Inderscience Publishers ?
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Old 06-28-14, 05:24 PM   #20
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I'm sensing a Nobel prize in physics.

I'm sensing someone who really needs to be given something meaningful to do.

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Old 06-28-14, 06:26 PM   #21
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I love it, replicates even. Nice work!
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Old 06-28-14, 06:33 PM   #22
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26 mph and you call that a hill?
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Old 06-28-14, 06:36 PM   #23
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Please repeat the tests with various forms of waving, slightly lifting fingers from the bar, maybe a head nod. Really any form of acknowledging that the other cyclist exists.

I think you also need to consider the amount of power and motivation lost by being denied the satisfaction of a wave or acknowledgement in return. I'm sure everyone dwells on how many cyclists ignored them for the next x kilometers of their ride and that affects performance.
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Old 06-28-14, 06:53 PM   #24
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Please repeat the tests with various forms of waving, slightly lifting fingers from the bar, maybe a head nod. Really any form of acknowledging that the other cyclist exists.

I think you also need to consider the amount of power and motivation lost by being denied the satisfaction of a wave or acknowledgement in return. I'm sure everyone dwells on how many cyclists ignored them for the next x kilometers of their ride and that affects performance.
This was a full arm wave, involving each degree of freedom of motion and to the fullest extent possible. I'm not planning on breaking it down more than that. You can take over with those tests if you wish but I suspect that the results would have limited utility.

Regarding the subjective effect on ride quality I can tell you this. With an exuberant arm wave it is difficult to refrain from lifting your torso, and when you do manage to keep your shoulders fixed relative to the bike, control is negatively impacted.

Studies of psychological impact are best left to the pseudo-scientific methods of the practitioners of the soft sciences, and alas, are beyond the scope of my inquiries.

edit: I may actually repeat with the head nod, because I expect that it actually would result in some measurable increase in drag, which I think would be surprising to almost everyone.

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Old 06-28-14, 06:57 PM   #25
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26 mph and you call that a hill?
I selected a gentle grade to simulate the realistic speeds of a roadie in training.
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