Do their claims measured in a wind tunnel pan out in a turbulent environment. Ask Hambini what he thinks :-
Why? SwissSide are one of the few who take transient flow into account in their testing and no one has seen evidence that Hambini actually did any of the testing he claims to have done.
And when has lab rolling resistance testing not panned out on real asphalt? I.e. which fast CRR tire is slow on the road?
Do their claims measured in a wind tunnel pan out in a turbulent environment. Ask Hambini what he thinks :-
Why? SwissSide are one of the few who take transient flow into account in their testing and no one has seen evidence that Hambini actually did any of the testing he claims to have done.
And when has lab rolling resistance testing not panned out on real asphalt? I.e. which fast CRR tire is slow on the road?
My point is CRR results on a real road vs a roller and drag results outdoor with a rider vs in a tunnel with unknow conditions (bike ?mannequin ?) can vary.
9 times out of 10, when I try to confirm manufacturerâs claims, I get different results. Maybe I am unlucky.
Which method(s) do you use?
Do their claims measured in a wind tunnel pan out in a turbulent environment. Ask Hambini what he thinks :-
Why? SwissSide are one of the few who take transient flow into account in their testing and no one has seen evidence that Hambini actually did any of the testing he claims to have done.
And when has lab rolling resistance testing not panned out on real asphalt? I.e. which fast CRR tire is slow on the road?
My point is CRR results on a real road vs a roller and drag results outdoor with a rider vs in a tunnel with unknow conditions (bike ?mannequin ?) can vary.
9 times out of 10, when I try to confirm manufacturerâs claims, I get different results. Maybe I am unlucky.
the guy that did some road testing with ditlev seems to have come to a similar conclusion but then magnus said when they went to tunnel using a grit not sure if this is the right term it works out better
but then magnus said when they went to tunnel using a grit not sure if this is the right term it works out better
Active turbulence grid
My active turbulence grid is courtesy of mother nature 
We can measure the turbulence but she wonât let us control it.
but then magnus said when they went to tunnel using a grit not sure if this is the right term it works out better
Active turbulence grid
My active turbulence grid is courtesy of mother nature We can measure the turbulence but she wonât let us control it.
this is all way above my pay grade but is this something like in the 4th or 5 pic behind the rider
https://bikerumor.com/swiss-side-hadron²-ultimate-aero-road-wheels-reshaped-for-faster-more-stable-aerodynamic-gains/
and why would you use it outside when it seems to occur outside anyways.
this is all way above my pay grade but is this something like in the 4th or 5 pic behind the rider
https://bikerumor.com/...e-aerodynamic-gains/
and why would you use it outside when it seems to occur outside anyways.
I am not sure I understand your question. Are you asking why you would try to create turbulence when turbulence already exists ?
No, the active turblence grid is not like that ârakeâ in the pic
here is one
https://youtu.be/lxTKSq2v7BY?si=eiW83OEmcjMzA-xb
BTW, this is all above my pay grade as well. I just measure
Which method(s) do you use?
We use an aerometer and various other sensors on the road.
this is all way above my pay grade but is this something like in the 4th or 5 pic behind the rider
https://bikerumor.com/...e-aerodynamic-gains/
and why would you use it outside when it seems to occur outside anyways.
I am not sure I understand your question. Are you asking why you would try to create turbulence when turbulence already exists ?
No, the active turblence grid is not like that ârakeâ in the pic
here is one
https://youtu.be/lxTKSq2v7BY?si=eiW83OEmcjMzA-xb
BTW, this is all above my pay grade as well. I just measure
good stuff cheers , my head is exploding now, and iam looking forward writing a mundane training program .and think about active turbulence grids later âŚ
in my little mind this came up âŚ
good stuff cheers , my head is exploding now, and iam looking forward writing a mundane training program .and think about active turbulence grids later âŚ
in my little mind this came up âŚ
https://www.youtube.com/watch?v=AtG1BRW0XNo
Yes, that is testing outdoors.
Tunnels are like the pool when it opens at 6AM and you are the first one in.
Do their claims measured in a wind tunnel pan out in a turbulent environment. Ask Hambini what he thinks :-
Why? SwissSide are one of the few who take transient flow into account in their testing and no one has seen evidence that Hambini actually did any of the testing he claims to have done.
And when has lab rolling resistance testing not panned out on real asphalt? I.e. which fast CRR tire is slow on the road?
My point is CRR results on a real road vs a roller and drag results outdoor with a rider vs in a tunnel with unknow conditions (bike ?mannequin ?) can vary.
9 times out of 10, when I try to confirm manufacturerâs claims, I get different results. Maybe I am unlucky.
My thoughts on transient vs quasi-static:
IMHO (and that goes for this entire post), bicycles experience quasi-static flow conditions for the majority of their use. This is to say that the speed of the maneuvers (rocking/steering/leaning/pedalling etc.) occur too slowly for the flow to be considered truly dynamic in nature. The flowfield on the body has reached a quasi steady state before the orientation of the body can change yet again - a particle in the flow will pass over the entire length of the body before the body can change its orientation significantly.
If one wants math, the quantities of interest are t_hat (non dimensional maneuver time) and t_star (t_star = L/V â the time needed for the flow to pass over the body). In order for the flow to be considered dynamic, and thus yield wind tunnel testing in a static environment invalid, t_hat generally must be less than ~3 (if my memory serves me right).
t_hat = t/t_star=(t*V)/L
where t is maneuver time, V is flow speed, and L is the length scale (chord length of a fork blade, rim depth, torso length, leg diameter etc.).
For bike parts, I simply donât think that maneuvers happen fast enough (nor are the length scales long enough) to make the quasi-static assumption break down - it is also assumed that beta angle sweeps in the tunnel are done for all cases one is trying to model. For the rider and her position, it becomes a possibility that the flow is on the verge of becoming fully dynamic (even then, I doubt it - though I donât know for sure), and only than at the lower speeds and only for the torso length scale & not leg diameters.
Iâm curious to hear what magnitudes you are trying to detect when you mention 9/10 times above? Picking the fly-sh!t out of the pepper is tough business! haha
9 times out of 10, when I try to confirm manufacturerâs claims, I get different results. Maybe I am unlucky.
Iâm curious to hear what magnitudes you are trying to detect when you mention 9/10 times above? Picking the fly-sh!t out of the pepper is tough business! haha
Well, the claims here are 5 watts in CRR and 4 watts in Aero at 30km/h, 17w at high yaw
That is pretty easy to see.
This is not fly shit, itâs elephant dumps
I tested last week a wheel with a claim of 12watts and a helmet with a claim of 13watts.
Manufacturers never claim 1 or 2w. Itâs always 8 and more. Pretty easy to confirm.
Do their claims measured in a wind tunnel pan out in a turbulent environment. Ask Hambini what he thinks :-
Why? SwissSide are one of the few who take transient flow into account in their testing and no one has seen evidence that Hambini actually did any of the testing he claims to have done.
And when has lab rolling resistance testing not panned out on real asphalt? I.e. which fast CRR tire is slow on the road?
My point is CRR results on a real road vs a roller and drag results outdoor with a rider vs in a tunnel with unknow conditions (bike ?mannequin ?) can vary.
9 times out of 10, when I try to confirm manufacturerâs claims, I get different results. Maybe I am unlucky.
My thoughts on transient vs quasi-static:
IMHO (and that goes for this entire post), bicycles experience quasi-static flow conditions for the majority of their use. This is to say that the speed of the maneuvers (rocking/steering/leaning/pedalling etc.) occur too slowly for the flow to be considered truly dynamic in nature. The flowfield on the body has reached a quasi steady state before the orientation of the body can change yet again - a particle in the flow will pass over the entire length of the body before the body can change its orientation significantly.
If one wants math, the quantities of interest are t_hat (non dimensional maneuver time) and t_star (t_star = L/V â the time needed for the flow to pass over the body). In order for the flow to be considered dynamic, and thus yield wind tunnel testing in a static environment invalid, t_hat generally must be less than ~3 (if my memory serves me right).
t_hat = t/t_star=(t*V)/L
where t is maneuver time, V is flow speed, and L is the length scale (chord length of a fork blade, rim depth, torso length, leg diameter etc.).
For bike parts, I simply donât think that maneuvers happen fast enough (nor are the length scales long enough) to make the quasi-static assumption break down - it is also assumed that beta angle sweeps in the tunnel are done for all cases one is trying to model. For the rider and her position, it becomes a possibility that the flow is on the verge of becoming fully dynamic (even then, I doubt it - though I donât know for sure), and only than at the lower speeds and only for the torso length scale & not leg diameters.
Iâm curious to hear what magnitudes you are trying to detect when you mention 9/10 times above? Picking the fly-sh!t out of the pepper is tough business! haha
This is on top of the fact that airflow coming onto the rider is mostly laminar or barely turbulent, unless youââŹâ˘re drafting. If youââŹâ˘re drafting aero doesnââŹâ˘t really matter that much. I expect real life conditions to be close to what we see in traditional tunnel testing. I also think they maybe injecting too much turbulence into the flow with what IââŹâ˘ve seen of transient setups they have in the tunnel, unless thatââŹâ˘s shown in their worst case configurations.
ItââŹâ˘s of course good to check if your designs fall apart in that regime, however itââŹâ˘s unlikely to have much of an effect on performance. I have a feeling that transient flow testing is more of a marketing tool than something very impactful.
To back this up, my understanding is that theyâre able to predict race performances pretty well based on wind tunnel data and power.
For $120/tire, not sure itââŹâ˘s worth it.
I just put one in my cart, figured for $120 I could try it out with my aero sensor and at least entertain myself for a bit with it. But they wanted $66 to ship it. So itâs not a $120 tire, itâs a $186 tire, at least if you live in the US. Hopefully the regular outlets get the tire.
Also, related to the front page article comment about âfirst ever aero tireâ, there used to be a Bontrager aero tire. Itâs gimmick was that it filled or smoothed out the gap between the wheel and the tire.
Thatâs odd, I just did a dummy order for one tire and the cart showed that shipping was free. Were you trying to get them overnighted or something?
Well, the claims here are 5 watts in CRR and 4 watts in Aero at 30km/h, 17w at high yaw
That is pretty easy to see.
This is not fly shit, itâs elephant dumps
I tested last week a wheel with a claim of 12watts and a helmet with a claim of 13watts.
Manufacturers never claim 1 or 2w. Itâs always 8 and more. Pretty easy to confirm.
lol - elephant dumps! love it! 
i come from a time when mfrâs didnât really claim watts - so maybe youâre right! 
looking at old data for a zipp 1080 and different tires rnâŚit looks like i reported the total axial force (in grams of dragâŚuggh!) for a wheel in isolation at 20 mph to be around 50grams for a variety of beta/sideslip anglesâŚor about 4 watts.
maybe this was the tire they were using on the comp wheel for your reported claim - haha:
This is on top of the fact that airflow coming onto the rider is mostly laminar or barely turbulent, unless youââŹâ˘re drafting. If youââŹâ˘re drafting aero doesnââŹâ˘t really matter that much. I expect real life conditions to be close to what we see in traditional tunnel testing. I also think they maybe injecting too much turbulence into the flow with what IââŹâ˘ve seen of transient setups they have in the tunnel, unless thatââŹâ˘s shown in their worst case configurations.
ItââŹâ˘s of course good to check if your designs fall apart in that regime, however itââŹâ˘s unlikely to have much of an effect on performance. I have a feeling that transient flow testing is more of a marketing tool than something very impactful.
To back this up, my understanding is that theyâre able to predict race performances pretty well based on wind tunnel data and power.
i think wind tunnels are a great tool in the toolbox for prod dev engineers/race engineers! field testing is another great independent line of inquiry. both require some experience/expertise, i reckon. weighing dollar bills with a truck scale (as John Cobb used to say) is tough work!
Well, the claims here are 5 watts in CRR and 4 watts in Aero at 30km/h, 17w at high yaw
âŚagain, itâs been a while for me since doing this stuff - so, forgive the question⌠Iâm assuming these are disc brake wheels+tires tested in isolation with the disc brake rotor installed? do you have any pics of the setup?
i ask, because the wind tunnel data I have with aero wheels/tires manufactured decades ago didnât have rotors installed, and the data above generally lines up really well with what iâd expectâŚand thatâs super cool to see! the only thing that catches my eye is that i would have expected some weirdness/high variance/asymmetry in cxa at low beta/yaw with a rotor installedâŚitâs a flat plate/disc with the aero props of a barn door after all. haha.
Tested without the disc rotor:
https://www.rennrad-news.de/news/continental-aero-111-reifen-dt-swiss-swiss-side-test/
.
Tested without the disc rotor:
https://www.rennrad-news.de/...iss-swiss-side-test/
thx for the link! I made some notes on the image below.
a few blurt outs:
blue dots are from 2009 zipp 1080+tangente tire (real data from a different wind tunnel)
red dots are maybe what the disc rotor penalty looks like?
gray dots are maybe what a narrow tire on the dt swiss wheel looks like?
âŚfat wheels over the past 15 years look to have pushed the stall point outâŚcool!
watch out for elephants! haha
