which wheels to get, (50-60mm)

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TobinHatesYou
Posts: 12443
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

deepakvrao wrote:
Wed Mar 13, 2019 1:06 am

I thought that he meant that when tyre and rim are well matched, the reason for the lower drag also leads to the poorer handling?

I guess we need to define what handling means. Is a wheel that wants to stay straight and stable better handling or worse?

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joshatsilca
Posts: 47
Joined: Thu Feb 21, 2019 4:52 pm

by joshatsilca

TobinHatesYou wrote:
Tue Mar 12, 2019 7:14 pm
I took it to mean that with tires that are too wide, the net sideforces acting on a deep wheel will be greater...adversely affecting “handling.” With a properly sized tire/rim pairing, drag is reduced, detachment on the leeward side is minimized, and the wheel should feel more stable in the wind. Hopefully Josh checks in and clarifies.
No, unfortunately it is the opposite. Think of it like an aircraft wing.. when the flow is attached the lift is high and the drag is low.. once there is separation the drag goes up and the lift drops (stall). In a wheel, the lift is the side force.. so the challenge iwth really aero wheels is that the lift component that helps negate the drag is also the part that makes handling such a challenge.. think of a front disc wheel.. it can be net zero to even negative drag.. but the lift component that is helping acheive that is a side force which is also making handling a challenge. When we did Firecrest almost 10 years ago now, the realization was that we could balance the side force components in a deep rim so that even when the side force was high, the torque would be low if we could get the center of pressure to be very close to the steering axis (and consistently there with yaw angle).

Josh
Owner of SILCA
Check out my Tech Blog: https://blog.silca.cc
Stories of the Tech behind the Tech: https://marginalgainspodcast.cc

alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

That's very interesting!
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joshatsilca
Posts: 47
Joined: Thu Feb 21, 2019 4:52 pm

by joshatsilca

TobinHatesYou wrote:
Wed Mar 13, 2019 1:09 am
deepakvrao wrote:
Wed Mar 13, 2019 1:06 am

I thought that he meant that when tyre and rim are well matched, the reason for the lower drag also leads to the poorer handling?

I guess we need to define what handling means. Is a wheel that wants to stay straight and stable better handling or worse?
This is an excellent point. Currently there is no industry standard for it and I think that the collective knowledge on what good handling really is, is still a bit lacking. When designing Firecrest, we initially thought that you wanted center of pressure behind the steering axis to create a sort of rudder effect on the front wheel, but it rode terrible and could be frightening in variable winds. I was discussing with Kim Blair at MIT and he was telling me about their attempt to model bicycle steering in the computer and how the challenge wasn't to model cornering but rather corner initiation because of the way counter steer works.. so to turn right, you have to first get the contact patch of the front tire to move to the left to give you the imbalance to lean right.. so a turn is initiated by a tiny countersteer in the beginning.

This makes total sense, it's why you can't get off of curbing if you end up in the gutter.. to lean to the side you need to lean you have to steer the contact patch into the curb..

So from there we modelled it and realized that if you get a gust of wind from the left, you want the wheel to steer to the right a little which will initiate a lean into the wind which you can then control by a combinatin of posture/hip english and turning.. If the gust turns the wheel into the wind, then the turn initiated is going in the direction of the wind and you have to then initiate a completely opposite correction. So for that product we tried to put the center of pressure as close to the steering axis as possible to minimize torque, while making sure that at all angles it was always in front of the steering axis.

However, ENVE, Reynolds and others have slightly different ideas on how/where to put the Cp and why..though everybody who is testing in tunnels with yaw torque measurement has so far followed the lead of putting the Cp in front of the axis. Sadly, half the brands I see touting 'handling' and showing their wind tunnel testing are at tunnels that can't measure what you need to measure to design for handling.. but that's another story.

Josh
Owner of SILCA
Check out my Tech Blog: https://blog.silca.cc
Stories of the Tech behind the Tech: https://marginalgainspodcast.cc

ichobi
Posts: 1793
Joined: Thu Jan 19, 2012 11:30 pm

by ichobi

I dont know if you can answer this Josh, but is it possible to tell us which wheel brands have put the most effort in r&d? Some brands like to talk about their development a lot say Zipp and Enve, some not so much like Campagnolo. All of them makes great wheels.

joshatsilca
Posts: 47
Joined: Thu Feb 21, 2019 4:52 pm

by joshatsilca

ichobi wrote:
Thu Mar 14, 2019 3:12 am
I dont know if you can answer this Josh, but is it possible to tell us which wheel brands have put the most effort in r&d? Some brands like to talk about their development a lot say Zipp and Enve, some not so much like Campagnolo. All of them makes great wheels.
ichobi, this is really hard to say at this point.. I know that when I left Zipp we estimated we spent roughly 3x what anybody else was spending on R&D, but a lot of that came from everything in that factory being done from scratch, so there was a wind tunnel team, layup team, tooling team, CFD team, materials experts.. we were also probably 40% of the global carbon wheel market at that point, so by the very nature of it we were the biggest spenders. So many companies/brands don't actually make anything themselves, so the R&D might only consist of wind tunnel testing or CFD or soemthing like that..

I will say that I thikn Zipp, ENVE, Specialized and Swisside are widely believed to do more wind tunnel than anybody else. When I left Zipp we had contracts in place with SanDiego to do 100 hours per year and were in process of building a custom balance at the ARC wind tunnel which is about a kilometer from Zipp headquarters, this is the sister tunnel to the Mercedes tunnel in England that ENVE/SimonSmart use but I'm not sure if that has them doing less or more testing.

I currently think that Swisside are doing the best combination of aero and education out there.. we used to pride ourselves on the education side of tunnel work and I just don't see that happening now in any of the other companies.

The other half of the money comes on the manufacturing side and really only Zipp, ENVE, Corima, and Shimano are actually making their own rims that I'm aware of.

Your mention of Campagnolo is an interseting one, we used to make stuff for them and they are just SOOOO conservative. Their wheels are very nicely made, but they are by design one generation behind what the cutting edge companies are doing as they are just to risk averse, Shimano is quite similar.

T
Owner of SILCA
Check out my Tech Blog: https://blog.silca.cc
Stories of the Tech behind the Tech: https://marginalgainspodcast.cc

sfo423
Posts: 736
Joined: Fri Dec 22, 2006 6:12 pm
Location: San Francisco

by sfo423

I was reading about Swiss Side working with DT Swiss on their top of the line wheels. What about FFWD and the DARC aero profile they have?

Snake oil?


joshatsilca wrote:
Thu Mar 14, 2019 5:59 pm
ichobi wrote:
Thu Mar 14, 2019 3:12 am
I dont know if you can answer this Josh, but is it possible to tell us which wheel brands have put the most effort in r&d? Some brands like to talk about their development a lot say Zipp and Enve, some not so much like Campagnolo. All of them makes great wheels.
ichobi, this is really hard to say at this point.. I know that when I left Zipp we estimated we spent roughly 3x what anybody else was spending on R&D, but a lot of that came from everything in that factory being done from scratch, so there was a wind tunnel team, layup team, tooling team, CFD team, materials experts.. we were also probably 40% of the global carbon wheel market at that point, so by the very nature of it we were the biggest spenders. So many companies/brands don't actually make anything themselves, so the R&D might only consist of wind tunnel testing or CFD or soemthing like that..

I will say that I thikn Zipp, ENVE, Specialized and Swisside are widely believed to do more wind tunnel than anybody else. When I left Zipp we had contracts in place with SanDiego to do 100 hours per year and were in process of building a custom balance at the ARC wind tunnel which is about a kilometer from Zipp headquarters, this is the sister tunnel to the Mercedes tunnel in England that ENVE/SimonSmart use but I'm not sure if that has them doing less or more testing.

I currently think that Swisside are doing the best combination of aero and education out there.. we used to pride ourselves on the education side of tunnel work and I just don't see that happening now in any of the other companies.

The other half of the money comes on the manufacturing side and really only Zipp, ENVE, Corima, and Shimano are actually making their own rims that I'm aware of.

Your mention of Campagnolo is an interseting one, we used to make stuff for them and they are just SOOOO conservative. Their wheels are very nicely made, but they are by design one generation behind what the cutting edge companies are doing as they are just to risk averse, Shimano is quite similar.

T

bas
Posts: 218
Joined: Thu Jun 30, 2016 3:58 am

by bas

I'm surprised HED aren't mentioned? Aren't they one of the pioneers of the current rim shapes, particularly with regard to the handling component?

clarinet5001
Posts: 32
Joined: Fri Jan 18, 2019 1:32 am

by clarinet5001

bas wrote:
Fri Mar 15, 2019 2:27 am
I'm surprised HED aren't mentioned? Aren't they one of the pioneers of the current rim shapes, particularly with regard to the handling component?
HED wheels are fantastic, they just tend to get passed over by 'real' weight weenies...


Also to add my .02c, the OP might as well choose based on which wheels are more aero. There's no great reason to buy carbon unless you pick something more aero than the best semi-aero alloy rims.

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