https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On Monday, September 12, 2022 at 9:21:52 AM UTC-4, AMuzi wrote:
> https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
>
>
> --
> Andrew Muzi
> <www.yellowjersey.org/>
> Open every day since 1 April, 1971

The picture above the "Aerobars" caption is a good illustration of the common misconception that the addition of aerobars inherently drops your CdA. Their two positions are pretty close save the arm position (generally agreed not to contribute much), and if the rider in the foreground were to stay in the drops with his forearms parallel to the ground, his position would be noticeably more aero. Here are a couple of handy graphics.

https://ars.els-cdn.com/content/image/1-s2.0-S0167610518305762-egi10SFBRNQBJF_lrg.jpg

https://ars.els-cdn.com/content/image/1-s2.0-S0167610518305762-egi10FV195WHDF_lrg.jpg

Frank and I had a pretty productive discussion on this a while back.

On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
> https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/

I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.

On Monday, September 12, 2022 at 10:55:21 AM UTC-4, funkma...@hotmail.com wrote:
> On Monday, September 12, 2022 at 9:21:52 AM UTC-4, AMuzi wrote:
> > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
> >
> >
> > --
> > Andrew Muzi
> > <www.yellowjersey.org/>
> > Open every day since 1 April, 1971
> The picture above the "Aerobars" caption is a good illustration of the common misconception that the addition of aerobars inherently drops your CdA. Their two positions are pretty close save the arm position (generally agreed not to contribute much), and if the rider in the foreground were to stay in the drops with his forearms parallel to the ground, his position would be noticeably more aero.

That word "inherently" is certainly worth emphasizing. I think that aerodynamic effects are very susceptible
to details. One person's aerobar setup and effects may be very different from the next person's.

I've had a friend remark, when he was drafting me and I was on my aerobars, "Wow, you get really low on
those things." Unlike Jan Heine, I'm quite comfortable on mine. But then, I'm not using them on gravel
where I need the suspension effect of my arms.

Other points in that article: They mention the need for at least a 3:1 ratio in a teardrop profile. I first
got interested in vehicle aerodynamics when I was in high school. That was when I read about the
"Kamm effect," the benefits of a gradual decrease in cross section area ending in a sudden chopping
off of the tail, instead of a faster reduction in cross section. Both methods can generate a practical
vehicle length (as opposed to a ridiculously long pointed tail). But if airflow can't follow the more
rapid taper, turbulence ensues starting with a large cross section and the taper does no good. (Think
of a VW Beetle.) Following Kamm, the area generating turbulence is much smaller.

About the handlebar bag discussion: I really do think they should not be rectangles with sharp corners.
I designed and built two of mine, including one that incorporates aero bars.. Mine are rounded in front
and lack external pockets. I certainly out-coast all my friends, even those heavier than me. Perhaps
that's why?

About aero spokes: I tried them on my front wheel many years ago. I first did a coast-down test with
just the front wheel using its original round spokes (probably 14-15-14), timing the seconds for
indicated speed to drop between two values (sorry, i don't remember details). I then rebuilt the same
wheel using oval spokes, expecting the coast down to take longer. It didn't! It was slower! The oval spokes
I installed seemed less aero than round ones.

> Here are a couple of handy graphics.
>
> https://ars.els-cdn.com/content/image/1-s2.0-S0167610518305762-egi10SFBRNQBJF_lrg.jpg
>
> https://ars.els-cdn.com/content/image/1-s2.0-S0167610518305762-egi10FV195WHDF_lrg.jpg
>
> Frank and I had a pretty productive discussion on this a while back.

That was an unusually good discussion.

- Frank Krygowski

On Monday, September 12, 2022 at 4:12:57 PM UTC+1, cycl...@gmail.com wrote:
> On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
> > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
>
> I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.
>
I don't know that there's anywhere in Ireland where the road is good enough, steep enough and long enough to attempt 82mph, but I did manage over the ton (truck assisted to get up speed on the previous uphill, morons) on a Dutch commuter bike, with the handlebar grips below the fork crown. I know that there will be very little or possibly no aero effect until a much higher speed than 62mph. However, the negative act of removing the blunt plane of all my chest muscles and oversized brain from the airstream must be worth something, all that area in the CdA formula in the airstream as one sits up in the normal position of a touring bike. To a cyclist the little margins help. Some people have ridiculous faith in a straight back, and it isn't a coincidence that they're the same people with a ludicrous faith in global warming. -- AJ
>

On Monday, September 12, 2022 at 11:40:40 AM UTC-4, frkr...@gmail.com wrote:
> On Monday, September 12, 2022 at 10:55:21 AM UTC-4, funkma...@hotmail.com wrote:
> > On Monday, September 12, 2022 at 9:21:52 AM UTC-4, AMuzi wrote:
> > > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
> > >
> > >
> > > --
> > > Andrew Muzi
> > > <www.yellowjersey.org/>
> > > Open every day since 1 April, 1971
> > The picture above the "Aerobars" caption is a good illustration of the common misconception that the addition of aerobars inherently drops your CdA. Their two positions are pretty close save the arm position (generally agreed not to contribute much), and if the rider in the foreground were to stay in the drops with his forearms parallel to the ground, his position would be noticeably more aero.
> That word "inherently" is certainly worth emphasizing. I think that aerodynamic effects are very susceptible
> to details. One person's aerobar setup and effects may be very different from the next person's.
>
> I've had a friend remark, when he was drafting me and I was on my aerobars, "Wow, you get really low on
> those things." Unlike Jan Heine, I'm quite comfortable on mine. But then, I'm not using them on gravel
> where I need the suspension effect of my arms.
>
> Other points in that article: They mention the need for at least a 3:1 ratio in a teardrop profile. I first
> got interested in vehicle aerodynamics when I was in high school. That was when I read about the
> "Kamm effect," the benefits of a gradual decrease in cross section area ending in a sudden chopping
> off of the tail, instead of a faster reduction in cross section. Both methods can generate a practical
> vehicle length (as opposed to a ridiculously long pointed tail). But if airflow can't follow the more
> rapid taper, turbulence ensues starting with a large cross section and the taper does no good. (Think
> of a VW Beetle.) Following Kamm, the area generating turbulence is much smaller.
>
> About the handlebar bag discussion: I really do think they should not be rectangles with sharp corners.
> I designed and built two of mine, including one that incorporates aero bars. Mine are rounded in front
> and lack external pockets. I certainly out-coast all my friends, even those heavier than me. Perhaps
> that's why?
>
> About aero spokes: I tried them on my front wheel many years ago. I first did a coast-down test with
> just the front wheel using its original round spokes (probably 14-15-14), timing the seconds for
> indicated speed to drop between two values (sorry, i don't remember details). I then rebuilt the same
> wheel using oval spokes, expecting the coast down to take longer. It didn't! It was slower! The oval spokes
> I installed seemed less aero than round ones.

My experience at the wind tunnel supports the Herse link paragraphs about bladed spokes and is similar to you experience. Bladed spokes really only offer benefits in consistent conditions, and in the real world may actually be detrimental, but hey, they look pretty cool. I had a set of Hed tri spokes for a while. I sold them after a semi went by me a little close and a little quick such that the turbulence almost took out the front wheel. I do know a couple of guys that used to swear by their Spinergy's though.

On Monday, September 12, 2022 at 2:57:45 PM UTC-7, Andre Jute wrote:
> On Monday, September 12, 2022 at 4:12:57 PM UTC+1, cycl...@gmail.com wrote:
> > On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
> > > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
> >
> > I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.
> >
> I don't know that there's anywhere in Ireland where the road is good enough, steep enough and long enough to attempt 82mph, but I did manage over the ton (truck assisted to get up speed on the previous uphill, morons) on a Dutch commuter bike, with the handlebar grips below the fork crown. I know that there will be very little or possibly no aero effect until a much higher speed than 62mph. However, the negative act of removing the blunt plane of all my chest muscles and oversized brain from the airstream must be worth something, all that area in the CdA formula in the airstream as one sits up in the normal position of a touring bike. To a cyclist the little margins help. Some people have ridiculous faith in a straight back, and it isn't a coincidence that they're the same people with a ludicrous faith in global warming. -- AJ
> >
My experience with Aero wheels isn't so much that they make you go faster but they seem to be less sensitive to side winds. The Campy Shamals and Sciroccos can suddenly jerk to the side with wind gusts. Not gripping the bars tightly on windy days does increase your speed since you dare to go faster without the worry of the wheel twisting.

On Wednesday, September 14, 2022 at 4:11:02 PM UTC-5, cycl...@gmail.com wrote:
> On Monday, September 12, 2022 at 2:57:45 PM UTC-7, Andre Jute wrote:
> > On Monday, September 12, 2022 at 4:12:57 PM UTC+1, cycl...@gmail.com wrote:
> > > On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
> > > > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
> > >
> > > I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.
> > >
> > I don't know that there's anywhere in Ireland where the road is good enough, steep enough and long enough to attempt 82mph, but I did manage over the ton (truck assisted to get up speed on the previous uphill, morons) on a Dutch commuter bike, with the handlebar grips below the fork crown. I know that there will be very little or possibly no aero effect until a much higher speed than 62mph. However, the negative act of removing the blunt plane of all my chest muscles and oversized brain from the airstream must be worth something, all that area in the CdA formula in the airstream as one sits up in the normal position of a touring bike. To a cyclist the little margins help. Some people have ridiculous faith in a straight back, and it isn't a coincidence that they're the same people with a ludicrous faith in global warming. -- AJ
> > >
> My experience with Aero wheels isn't so much that they make you go faster but they seem to be less sensitive to side winds.

And Tommy says the exact opposite of what every other bicycle rider and engineer in the whole world has said about aero wheels. Everyone else on earth, notices the bigger surface area of the aero wheels makes them MORE sensitive to side winds. But Tommy says the opposite. Surprising. Tommy, when you are out sailing with your yacht club, use a towel for a sail. Not the 300 square foot sail. The towel will catch more wind and make you sail faster.

> The Campy Shamals and Sciroccos can suddenly jerk to the side with wind gusts. Not gripping the bars tightly on windy days does increase your speed since you dare to go faster without the worry of the wheel twisting.

On Wed, 14 Sep 2022 18:19:14 -0700 (PDT), "russellseaton1@yahoo.com"
<ritzannaseaton@gmail.com> wrote:

>On Wednesday, September 14, 2022 at 4:11:02 PM UTC-5, cycl...@gmail.com wrote:
>> On Monday, September 12, 2022 at 2:57:45 PM UTC-7, Andre Jute wrote:
>> > On Monday, September 12, 2022 at 4:12:57 PM UTC+1, cycl...@gmail.com wrote:
>> > > On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
>> > > > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
>> > >
>> > > I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.
>> > >
>> > I don't know that there's anywhere in Ireland where the road is good enough, steep enough and long enough to attempt 82mph, but I did manage over the ton (truck assisted to get up speed on the previous uphill, morons) on a Dutch commuter bike, with the handlebar grips below the fork crown. I know that there will be very little or possibly no aero effect until a much higher speed than 62mph. However, the negative act of removing the blunt plane of all my chest muscles and oversized brain from the airstream must be worth something, all that area in the CdA formula in the airstream as one sits up in the normal position of a touring bike. To a cyclist the little margins help. Some people have ridiculous faith in a straight back, and it isn't a coincidence that they're the same people with a ludicrous faith in global warming. -- AJ
>> > >
>> My experience with Aero wheels isn't so much that they make you go faster but they seem to be less sensitive to side winds.
>
>And Tommy says the exact opposite of what every other bicycle rider and engineer in the whole world has said about aero wheels. Everyone else on earth, notices the bigger surface area of the aero wheels makes them MORE sensitive to side winds. But Tommy says the opposite. Surprising. Tommy, when you are out sailing with your yacht club, use a towel for a sail. Not the 300 square foot sail. The towel will catch more wind and make you sail faster.
>

Well, Tommy has a history of not being able to install things on
bicycles correctly so perhaps he installed the aero spokes twisted so
that the "streamlining" is at 90 degrees to the rim. Viola! Less cross
wind drag.
--
Cheers,

John B.

On Wednesday, September 14, 2022 at 9:22:04 PM UTC-5, John B. wrote:
> On Wed, 14 Sep 2022 18:19:14 -0700 (PDT), "russell...@yahoo.com"
> <ritzann...@gmail.com> wrote:
>
> >On Wednesday, September 14, 2022 at 4:11:02 PM UTC-5, cycl...@gmail.com wrote:
> >> On Monday, September 12, 2022 at 2:57:45 PM UTC-7, Andre Jute wrote:
> >> > On Monday, September 12, 2022 at 4:12:57 PM UTC+1, cycl...@gmail.com wrote:
> >> > > On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
> >> > > > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
> >> > >
> >> > > I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.
> >> > >
> >> > I don't know that there's anywhere in Ireland where the road is good enough, steep enough and long enough to attempt 82mph, but I did manage over the ton (truck assisted to get up speed on the previous uphill, morons) on a Dutch commuter bike, with the handlebar grips below the fork crown. I know that there will be very little or possibly no aero effect until a much higher speed than 62mph. However, the negative act of removing the blunt plane of all my chest muscles and oversized brain from the airstream must be worth something, all that area in the CdA formula in the airstream as one sits up in the normal position of a touring bike. To a cyclist the little margins help. Some people have ridiculous faith in a straight back, and it isn't a coincidence that they're the same people with a ludicrous faith in global warming. -- AJ
> >> > >
> >> My experience with Aero wheels isn't so much that they make you go faster but they seem to be less sensitive to side winds.
> >
> >And Tommy says the exact opposite of what every other bicycle rider and engineer in the whole world has said about aero wheels. Everyone else on earth, notices the bigger surface area of the aero wheels makes them MORE sensitive to side winds. But Tommy says the opposite. Surprising. Tommy, when you are out sailing with your yacht club, use a towel for a sail. Not the 300 square foot sail. The towel will catch more wind and make you sail faster.
> >
> Well, Tommy has a history of not being able to install things on
> bicycles correctly so perhaps he installed the aero spokes twisted so
> that the "streamlining" is at 90 degrees to the rim. Viola! Less cross
> wind drag.
> --
> Cheers,
>
> John B.

But the deep section rim on aero wheels is what catches the wind. Not the spokes. The spokes make up a tiny portion of the surface area the wind hits. But given Tommy, maybe he installed both of the wheels 90 degrees to the wind. And rode sideways.

On Wed, 14 Sep 2022 20:10:47 -0700 (PDT), "russellseaton1@yahoo.com"
<ritzannaseaton@gmail.com> wrote:

>On Wednesday, September 14, 2022 at 9:22:04 PM UTC-5, John B. wrote:
>> On Wed, 14 Sep 2022 18:19:14 -0700 (PDT), "russell...@yahoo.com"
>> <ritzann...@gmail.com> wrote:
>>
>> >On Wednesday, September 14, 2022 at 4:11:02 PM UTC-5, cycl...@gmail.com wrote:
>> >> On Monday, September 12, 2022 at 2:57:45 PM UTC-7, Andre Jute wrote:
>> >> > On Monday, September 12, 2022 at 4:12:57 PM UTC+1, cycl...@gmail.com wrote:
>> >> > > On Monday, September 12, 2022 at 6:21:52 AM UTC-7, AMuzi wrote:
>> >> > > > https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/
>> >> > >
>> >> > > I no longer believe in any of this aero crap since the normal rider never rides fast enough for aerodynamic drag to come into the picture. Pro's riding 25 or more mph for hours on end may very well gain a benefit but pretending that Joe pretend racer is gaining anything is silly. That 87 mph 2 minute descent I made was with Campy Shamal new style box rims with very wide carbon spokes. I doubt I would have gone any faster if I had used aero wheels since that was about as fast as I dared. And I took up a lot of road doing that.
>> >> > >
>> >> > I don't know that there's anywhere in Ireland where the road is good enough, steep enough and long enough to attempt 82mph, but I did manage over the ton (truck assisted to get up speed on the previous uphill, morons) on a Dutch commuter bike, with the handlebar grips below the fork crown. I know that there will be very little or possibly no aero effect until a much higher speed than 62mph. However, the negative act of removing the blunt plane of all my chest muscles and oversized brain from the airstream must be worth something, all that area in the CdA formula in the airstream as one sits up in the normal position of a touring bike. To a cyclist the little margins help. Some people have ridiculous faith in a straight back, and it isn't a coincidence that they're the same people with a ludicrous faith in global warming. -- AJ
>> >> > >
>> >> My experience with Aero wheels isn't so much that they make you go faster but they seem to be less sensitive to side winds.
>> >
>> >And Tommy says the exact opposite of what every other bicycle rider and engineer in the whole world has said about aero wheels. Everyone else on earth, notices the bigger surface area of the aero wheels makes them MORE sensitive to side winds. But Tommy says the opposite. Surprising. Tommy, when you are out sailing with your yacht club, use a towel for a sail. Not the 300 square foot sail. The towel will catch more wind and make you sail faster.
>> >
>> Well, Tommy has a history of not being able to install things on
>> bicycles correctly so perhaps he installed the aero spokes twisted so
>> that the "streamlining" is at 90 degrees to the rim. Viola! Less cross
>> wind drag.
>> --
>> Cheers,
>>
>> John B.
>
>But the deep section rim on aero wheels is what catches the wind. Not the spokes. The spokes make up a tiny portion of the surface area the wind hits. But given Tommy, maybe he installed both of the wheels 90 degrees to the wind. And rode sideways.

What you really need is disc wheels. Super streamlined (:-)
https://slate.com/culture/2012/08/track-cycling-wheels-why-do-olympic-cyclists-use-disc-wheels.html
--
Cheers,

John B.