"Lightness" vs "Aeroness" UPDATED 10/2023

[Lina]

The results are bad because clearly whoever rode the Timemachine can't ride in an aero position and they can't descent. And they've all got different kit. So none of the results matter.

[HBike]

^ agreed that one piece cockpit is a marketing gain only once a Garmin computer and front light are fitted, but they sure look pretty.

If a manufacturer came up with an aero fully streamlined computer and front light mount I would believe the aero gains more.

The chap from tour suggested the additional drag from a bike computer was below their margin of error.

I'm not convinced all gains, relative to a two piece are thrown away by a computer and light.

It would be good to know more about this. I have heard the same opinion that mounting a computer doesn't make a measurable aero difference. But that doesn't account for the small and localised disruption to airflow an out front computer would cause.

My reasoning is that with like for like shapes the only tangible difference between a one piece and two piece bar is at the point the bar and stem join. That includes the stem screws, front plate and rounded bars in the clamping area.

From an air flow perspective a computer and front light obscures that particular area almost totally, so logically what else could a one piece offer over a 2 piece?

I have heard the same bits of contradicting test result info.

Perhaps one way to make sense of it - The addition of a bike computer doesn't do anything to a bike with a two piece stem/bar.

But it would tank the results of a bike with a 1 piece aerodynamic stem.

In other words, throw a bluff body in front of the stem, and the flow is turbulent. After that, doesn't matter if the stem itself is also a bluff body. And if the stem is a bluff body, then having another one in front of it makes no difference, it's gonna get forced turbulent by the stem a moment later anyway.

Just evidence-free speculation ¯\_(ツ)_/¯

As a fluid dynamicist I have to say this is wrong. The flow is changed by a bike computer in both cases. Therefore pressure distributions are changed. It may be that a bad two-piece handlepar configuration doesn't worsen aero, but a well designed one can (form, edges, screw postion, bike computer inclination, etc. all have an impact).
A short search out of curiosity pointed me to this
https://www.dcrainmaker.com/2017/05/wah ... sting.html

[alanyu]

First, as I've already posted in other thread, the modern head unit is not tall enough to shield all four bolts on a classic stem. It can only shield 1/2-2/3 of the stem height.

Second, with the unit close enough regarded as a "bad shielding", the (much) more important thing is how the trailing edge is (how the airflow detachs). This is what truely makes a good 1-piece aero barstem faster than an aero bar and a classic stem. To my knowledge, some stems has a smooth frontal cover/reversed bolt design like 3T and Pro one, but none of them are designed with the concept as a trailing edge. This is what a 1-piece can do. Also 1-piece could have a much lower overall height.

EXS's figure can illustrate the second point to a certain degree.

[Nereth]

The chap from tour suggested the additional drag from a bike computer was below their margin of error.

I'm not convinced all gains, relative to a two piece are thrown away by a computer and light.

It would be good to know more about this. I have heard the same opinion that mounting a computer doesn't make a measurable aero difference. But that doesn't account for the small and localised disruption to airflow an out front computer would cause.

My reasoning is that with like for like shapes the only tangible difference between a one piece and two piece bar is at the point the bar and stem join. That includes the stem screws, front plate and rounded bars in the clamping area.

From an air flow perspective a computer and front light obscures that particular area almost totally, so logically what else could a one piece offer over a 2 piece?

I have heard the same bits of contradicting test result info.

Perhaps one way to make sense of it - The addition of a bike computer doesn't do anything to a bike with a two piece stem/bar.

But it would tank the results of a bike with a 1 piece aerodynamic stem.

In other words, throw a bluff body in front of the stem, and the flow is turbulent. After that, doesn't matter if the stem itself is also a bluff body. And if the stem is a bluff body, then having another one in front of it makes no difference, it's gonna get forced turbulent by the stem a moment later anyway.

Just evidence-free speculation ¯\_(ツ)_/¯

As a fluid dynamicist I have to say this is wrong. The flow is changed by a bike computer in both cases. Therefore pressure distributions are changed. It may be that a bad two-piece handlepar configuration doesn't worsen aero, but a well designed one can (form, edges, screw postion, bike computer inclination, etc. all have an impact).
A short search out of curiosity pointed me to this
https://www.dcrainmaker.com/2017/05/wah ... sting.html

You're not wrong, but I what I'm trying to make sense of is the conflict between "Computer doesn't cause a measureable change in drag" and "the bar/stem connection/transition matters".

So I'm speculating, maybe the first claim isn't made with respect to a "well-designed" bar clamp. Maybe it's a big bulky ugly one that protrudes outside the frontal cross section of the computer, and also has a bad transition that trips the flow almost immediately. Maybe it ceases to be true with a better bar/stem combo - either a well designed 2 piece, or a 1 piece.

Also I agree that basically everything will make a difference, when I/we/tour magazin say "no difference" I think we're talking about whether that difference becomes small enough to be negligible compared to our experimental error (i.e. less than about a watt, from the looks of it).

[SixThirteen]

It would be good to know more about this. I have heard the same opinion that mounting a computer doesn't make a measurable aero difference. But that doesn't account for the small and localised disruption to airflow an out front computer would cause.

My reasoning is that with like for like shapes the only tangible difference between a one piece and two piece bar is at the point the bar and stem join. That includes the stem screws, front plate and rounded bars in the clamping area.

From an air flow perspective a computer and front light obscures that particular area almost totally, so logically what else could a one piece offer over a 2 piece?

I have heard the same bits of contradicting test result info.

Perhaps one way to make sense of it - The addition of a bike computer doesn't do anything to a bike with a two piece stem/bar.

But it would tank the results of a bike with a 1 piece aerodynamic stem.

In other words, throw a bluff body in front of the stem, and the flow is turbulent. After that, doesn't matter if the stem itself is also a bluff body. And if the stem is a bluff body, then having another one in front of it makes no difference, it's gonna get forced turbulent by the stem a moment later anyway.

Just evidence-free speculation ¯\_(ツ)_/¯

As a fluid dynamicist I have to say this is wrong. The flow is changed by a bike computer in both cases. Therefore pressure distributions are changed. It may be that a bad two-piece handlepar configuration doesn't worsen aero, but a well designed one can (form, edges, screw postion, bike computer inclination, etc. all have an impact).
A short search out of curiosity pointed me to this
https://www.dcrainmaker.com/2017/05/wah ... sting.html

You're not wrong, but I what I'm trying to make sense of is the conflict between "Computer doesn't cause a measureable change in drag" and "the bar/stem connection/transition matters".

So I'm speculating, maybe the first claim isn't made with respect to a "well-designed" bar clamp. Maybe it's a big bulky ugly one that protrudes outside the frontal cross section of the computer, and also has a bad transition that trips the flow almost immediately. Maybe it ceases to be true with a better bar/stem combo - either a well designed 2 piece, or a 1 piece.

Also I agree that basically everything will make a difference, when I/we/tour magazin say "no difference" I think we're talking about whether that difference becomes small enough to be negligible compared to our experimental error (i.e. less than about a watt, from the looks of it).

There's a thread on here about the SystemSix, and Damon mentions that they tested various positions of a bike computer, and the position that tested fasted was where the computer sits on top of the stem.

[bmrk]

I have heard the same bits of contradicting test result info.

Perhaps one way to make sense of it - The addition of a bike computer doesn't do anything to a bike with a two piece stem/bar.

But it would tank the results of a bike with a 1 piece aerodynamic stem.

In other words, throw a bluff body in front of the stem, and the flow is turbulent. After that, doesn't matter if the stem itself is also a bluff body. And if the stem is a bluff body, then having another one in front of it makes no difference, it's gonna get forced turbulent by the stem a moment later anyway.

Just evidence-free speculation ¯\_(ツ)_/¯

As a fluid dynamicist I have to say this is wrong. The flow is changed by a bike computer in both cases. Therefore pressure distributions are changed. It may be that a bad two-piece handlepar configuration doesn't worsen aero, but a well designed one can (form, edges, screw postion, bike computer inclination, etc. all have an impact).
A short search out of curiosity pointed me to this
https://www.dcrainmaker.com/2017/05/wah ... sting.html

You're not wrong, but I what I'm trying to make sense of is the conflict between "Computer doesn't cause a measureable change in drag" and "the bar/stem connection/transition matters".

So I'm speculating, maybe the first claim isn't made with respect to a "well-designed" bar clamp. Maybe it's a big bulky ugly one that protrudes outside the frontal cross section of the computer, and also has a bad transition that trips the flow almost immediately. Maybe it ceases to be true with a better bar/stem combo - either a well designed 2 piece, or a 1 piece.

Also I agree that basically everything will make a difference, when I/we/tour magazin say "no difference" I think we're talking about whether that difference becomes small enough to be negligible compared to our experimental error (i.e. less than about a watt, from the looks of it).

There's a thread on here about the SystemSix, and Damon mentions that they tested various positions of a bike computer, and the position that tested fasted was where the computer sits on top of the stem.

This will for sure depend on stem angle, width and computer width.


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[iflyadesk]

As far as I know Tour is reliable and independent source ( numbers what Tour publish)
They also tell components and model what they have tested, and they have exact and public testing protocol.
One downside is that they dont publish aerocurve, only -one weighted number-, which doenst tell bikes "aeroprofile".

They did—briefly—but stopped publishing it. This is very old. Like 2017 I think but not entirely sure.





I'm not a roadie anymore but I will say the times I REALLY felt the difference between an aero bike and a regular bike was on a really fast group ride when I was 10 wheels back hanging on by my fingernails and we had a brutally strong crosswind. The difference was MASSIVE. On the non-aero bike it felt as if someone had grabbed onto my seatpost and I was pulling them too.

[C36]

There's a thread on here about the SystemSix, and Damon mentions that they tested various positions of a bike computer, and the position that tested fasted was where the computer sits on top of the stem.

Recall this and 3 brands who tested it claimed they don’t understand how they got those results.

[Nickldn]

There's a thread on here about the SystemSix, and Damon mentions that they tested various positions of a bike computer, and the position that tested fasted was where the computer sits on top of the stem.

Recall this and 3 brands who tested it claimed they don’t understand how they got those results.

I would suspect that you would need a heroically accurate wind tunnel to measure at the resolution required to discern between different computers and mounting positions.

I also suspect a wind tunnel like this doesn't actually exist and what we have here is a set of imagined results.

[GrassQ]

I'm not a roadie anymore but I will say the times I REALLY felt the difference between an aero bike and a regular bike was on a really fast group ride when I was 10 wheels back hanging on by my fingernails and we had a brutally strong crosswind. The difference was MASSIVE. On the non-aero bike it felt as if someone had grabbed onto my seatpost and I was pulling them too.

Yes. Those aeroprofiles/-curves show that in certain condititions and wind (high yaw angles) , differences could be much bigger than in low wind/yaw angles (and probably also much bigger than "weighted one number" shows)

[cleanneon98]

Having gone from a non arro 2016 Emonda with Aeolus 5 wheels, to a 2024 Madone with Aeolus RSL51 wheels I can confirm the felt difference in winds is huge and the complete opposite of what I expected. I get blown around by strong gusts way less on the Madone, and riding into a head/cross wind also feels much more stable and faster. I expected the Madone to do worse in crosswinds since it has deeper profiles on the frame and fork. Sure the wheels are different too but the Emonda had the first generation D3 shaped wheels which were pretty good for their time.

I haven't tried it on group rides yet but looking forward to it