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importance of tyre aero vs rolling resistance data
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I am looking for race day tires and have read many of the previous treads on this, but I havent reaaly found any hard facts of the importance of aero vs rolling resistance for tires.
Should one choose aero over crr or the other way around?
I see the bontrager R4 aero scores pretty good in the biketech list on crr, so might be a good choice if aero characteristics are as good as claimed.
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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choose both!

it gets pretty hair splitting, find a tire with good crr, consider narrow especially up front. r4 is a great choice, zipp tangente is a great choice, some of the new continentals as well.



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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Personally I've always sided in the Crr camp. Here is my reasoning for better or worse.

Aero data is usually sited as a 'moment in time' or at X yaw it is Y better, and usually not a bunch better (for the tires at least).
Crr is all the time. No matter the speed, wind etc. it is always there.
Plus i'm a bigger rider so my Aero equation is less effected due to my larger over all size (the increase in aero efficiency of the tire is a smaller part of my total drag).
Again my Crr should become more important as my weight goes up.

This is your life, and it's ending one minute at a time. - Fight Club
Industry Brat.
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Re: importance of tyre aero vs rolling resistance data [Ti T'war] [ In reply to ]
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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Really? I thought bad Crr was bad Crr no matter the speed.
Or are you saying that Bad Crr gets worse the faster you go? That I'll buy, I was just thinking that there is a point where aerodynamics becomes an insignificant part of moving forward, where bad Crr is slowing you down at any speed.

This is your life, and it's ending one minute at a time. - Fight Club
Industry Brat.
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Re: importance of tyre aero vs rolling resistance data [Ti T'war] [ In reply to ]
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Ti T'war wrote:
I was just thinking that there is a point where aerodynamics becomes an insignificant part of moving forward, .

there is, but its like 10mph, pretty slow.



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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Thanks for the quick response so far.
So I guess one way to investigate tyre aero would be to compare wind tunnel drag data at different yaw angles for the same wheelset with different tyres attached.
Have any such information been made available online?
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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brynjulf wrote:
Thanks for the quick response so far.
So I guess one way to investigate tyre aero would be to compare wind tunnel drag data at different yaw angles for the same wheelset with different tyres attached.
Have any such information been made available online?

there is a bit of tire/aero/wheel data scattered around but you aren't going to get a definitive comparison you are looking for.

what wheels are you using?



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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jackmott wrote:
crr is in fact, less there when you go slower, just like aero =)

Does Crr change or just rr?
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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I will be on Flo60s in july, so quite wide rim which I understand might be relevant in tyre choice.
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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jackmott wrote:
Ti T'war wrote:
I was just thinking that there is a point where aerodynamics becomes an insignificant part of moving forward, .


there is, but its like 10mph, pretty slow.

~10mph is about where aero drag is about equal to rolling resistance, not where it's an insignificant fraction of the total.
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Re: importance of tyre aero vs rolling resistance data [JollyRogers] [ In reply to ]
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Crr has a moderate correlation to total tire deflection (weight/pressure) but I'd be pretty surprised if we could actually measure a difference in Crr with velocity (which is, in effect, the speed of deformation of the tire at the contact patch).

So I'm going with rr, not Crr.

The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important.

-Albert J. Nock
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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brynjulf wrote:
I will be on Flo60s in july, so quite wide rim which I understand might be relevant in tyre choice.

a known quantity that is aero and good RR is the zipp tangente 21mm

the r4 would be a fine choice as well.



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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Thanks for all the advice.
Jon from Flo cycling told me today that they have also tested their wheels with the Vittoria open corsa evo cx, and this combo produced 50 grams more drag than when the michelin pro3 tires were put on. To me that sounds like a huge difference. I was considering the vittoria tires based on low rolling resistance. Kind of sad to see halv of the improved performance of getting aero wheels go away simply by putting the wrong tires on... We need more wind tunnel data on tire/wheel combinations.
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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that is a huge difference
but what size of each tire?
how carefully did they control the test?
wind tunnel testing ain't easy, are there other reports of the vittoria being that bad aero-wise?

maybe the vittoria 23 is horrid but the 21 is great.


brynjulf wrote:
Thanks for all the advice.
Jon from Flo cycling told me today that they have also tested their wheels with the Vittoria open corsa evo cx, and this combo produced 50 grams more drag than when the michelin pro3 tires were put on. To me that sounds like a huge difference. I was considering the vittoria tires based on low rolling resistance. Kind of sad to see halv of the improved performance of getting aero wheels go away simply by putting the wrong tires on... We need more wind tunnel data on tire/wheel combinations.



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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CRR(mass)(velocity)=power required for the rolling resistance part of moving a bike at a given velocity. The crr doesn't change with speed.
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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If you haven't, read this: http://forum.slowtwitch.com/...tring=tires;#1778158

The faster you are, the more aero matters. If you're within a hand full of seconds to being on the podium, select one of the already name choices that perform well in both areas. If you're slower (and I'll throw out 35kph as a very, very rough cutoff) you'll see more difference just focusing on the crr component.
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Re: importance of tyre aero vs rolling resistance data [jackmott] [ In reply to ]
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jackmott wrote:
that is a huge difference
but what size of each tire?

Both 23mm tires.

how carefully did they control the test?

Same wind tunnel, same day, same wheel, exact same test, one right after the other.

wind tunnel testing ain't easy, are there other reports of the vittoria being that bad aero-wise?

maybe the vittoria 23 is horrid but the 21 is great.


brynjulf wrote:
Thanks for all the advice.
Jon from Flo cycling told me today that they have also tested their wheels with the Vittoria open corsa evo cx, and this combo produced 50 grams more drag than when the michelin pro3 tires were put on. To me that sounds like a huge difference. I was considering the vittoria tires based on low rolling resistance. Kind of sad to see halv of the improved performance of getting aero wheels go away simply by putting the wrong tires on... We need more wind tunnel data on tire/wheel combinations.


Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling
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Re: importance of tyre aero vs rolling resistance data [Canadian] [ In reply to ]
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Chris: what are your thoughts on the michelin pro 4 series? Do you think they will be as good a match as the pro 3?
Anyone else with experience with these tyres?
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Re: importance of tyre aero vs rolling resistance data [Canadian] [ In reply to ]
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Chris,

Thanks a lot for sharing !
Don't know if you could do that but it would be awsome if you could make a graph with the curves of both the Pro Race 3 700x23 and Corsa CX 23 700x23 on the same wheel at the different angles. You would really be the first company to show this information on same wheel and I think even though it's only two tires that's exactly what everybody wants to see here !!!

Hopefully you can make this information available (and even add it on your website to show how important tire choice is), thanks in advance !!! ;-)
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Re: importance of tyre aero vs rolling resistance data [brynjulf] [ In reply to ]
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brynjulf wrote:
Chris: what are your thoughts on the michelin pro 4 series? Do you think they will be as good a match as the pro 3?
Anyone else with experience with these tyres?

I just read through Michelin's website about the Pro 4 series tires. There doesn't appear to be many (if any) changes at all effecting aerodynamics and several performance improvements, eg. better grip, lighter weight, better puncture resistance. I'm guessing the Pro 4 will be just as good if not better.

Take care,


Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling
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Re: importance of tyre aero vs rolling resistance data [pyf] [ In reply to ]
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pyf wrote:
Chris,

Thanks a lot for sharing !
Don't know if you could do that but it would be awsome if you could make a graph with the curves of both the Pro Race 3 700x23 and Corsa CX 23 700x23 on the same wheel at the different angles. You would really be the first company to show this information on same wheel and I think even though it's only two tires that's exactly what everybody wants to see here !!!

Hopefully you can make this information available (and even add it on your website to show how important tire choice is), thanks in advance !!! ;-)

The information is certainly interesting but it can be misleading as well. You have to take into account that there are more things that contribute to tire selection than aerodynamic performance. Let me try to explain...

We chose the two tires you listed above because they are both good all around tires. For example, they have similar rolling resistances (fairly low actually), they both corner well, they are both pretty lightweight etc etc etc.

If we were to test additional tires then those tires may have rolling resistance values that counter any aero benefit you may gain, OR perhaps the tires lack grip in corners or in wet conditions. If a tire doesn't corner well and the rider on the bike knows that, they will be hesitant going into corners. In a race like a crit where you can have dozens of corners, holding back on every corner will cost you far more time than a 50gram aero benefit.

I guess the point I'm trying to make is that we don't want people to get overly hung up on having the "the most aero tire". As I said above... the tire may be super aero but if it isn't worth riding, who cares?

All in all, the vittoria was up to 50 grams slower. You can basically just move the curves we have put together up 50 grams to give yourself a pretty good idea of where the vittoria tires would be.

I hope that makes sense. Please let me know if you have any additional questions.


Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling
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Re: importance of tyre aero vs rolling resistance data [Canadian] [ In reply to ]
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To what do you attribute the difference in drag? The tire profile? The rim interface?

What's your theory about how the tire itself, in the same width, can make such a dramatic difference?
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Re: importance of tyre aero vs rolling resistance data [jyeager] [ In reply to ]
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Tire size generally changes the drag curve, a shift up or down is generally a change in tire size, a change in tire shape can dramatically change the drag curve.
Here's some tunnel data comparing a few different tires on the 303 FC carbon clincher (internally coded x45FC). you see that the GP4000 23 and 25mm are similar curve shapes, only shifted in magnitude, while the Attack despite being narrower has a different curve shape due to the different tire shape...the Michelin PR3 measures over 24mm wide despite the 23mm printed on the casing, but the shape of the tire has changed everything, especially when you consider that the GP4000 25mm is still 1mm wider.
I've thrown a V shaped wheel in for good measure, you see that tires can have nearly as much affect on aero as rim shape. Ultimately, the most aero tires are all pretty close together for a given width, maybe running 10-15 grams different between them, while the less aero tires can really spoil the party. The PR4 performs better than the PR3 here, so I'm not trying to call out Michelin, this is just a good example of the effect of tire choice. Also, the Michelin 20mm measures more like 22.3mm, and performs between the Conti 23 and 25 curves below, so I'm purely using this to illustrate a point.

Kraig Willet has a great piece about this on his site, he even has data comparing Tangentes, Bontrager wing tires, Veloflex and some others... I recommend it. he also talks about comparing rolling resistance between the tires and offsetting the data relative to the aero charts...good stuff. http://www.biketechreview.com
Josh



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Re: importance of tyre aero vs rolling resistance data [jyeager] [ In reply to ]
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jyeager wrote:
To what do you attribute the difference in drag? The tire profile? The rim interface?

What's your theory about how the tire itself, in the same width, can make such a dramatic difference?

First of all thanks to Josh for posting that data. Now I get to follow Josh on an aero topic... which is kind of like following Joe Montana on how to throw a football ;)

To answer your question my theory is that there are 3 contributing factors, tire shape/size, how that tire interacts with the wheel of choice, and possibly the tire tread itself (eg, the PR3 is a smooth tire and the Vitoria Open Corsa Evo CX II has a tread pattern). In all honesty we haven't spent much time studying tires in the tunnel. You can be sure however, that the next time we are in the wind tunnel we will be looking into this topic in greater detail.

Take care,


Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling
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