Is my math right? Aero bikes

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Krackor
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by Krackor

dton13 wrote:I think you're seriously over compensating for the difference that equipment makes - in road races/crits anyways. 13 seconds its not a small margin by any means. Aero gains are small margins in the grand scheme of things.

I don't think anyone can expect that a tactical mistake be covered up by some better equipment. I certainly never blame my bike for my losses, nor do I thank it for my wins.

Sagan rode for around ~15 minutes after the Paterberg until the finish. 13 seconds is 1.4% of 15 minutes. Over that duration, 1.4% time difference is only a 3-4% difference in Power/CdA ratio. (Time is inversely proportional to speed, and speed is inversely proportional to square or cube root of CdA. 1.014^3 = 1.04)

Small gains are better than no gains at all, and these gains are not as small and inconsequential as claimed by the math illiterate that frequent the aero threads.

mimason
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by mimason

mbrider, based on your added feedback you definitely want a power meter for your training and calculated riding you do.

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dton13
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by dton13

Krackor wrote:Sagan rode for around ~15 minutes after the Paterberg until the finish. 13 seconds is 1.4% of 15 minutes. Over that duration, 1.4% time difference is only a 3-4% difference in Power/CdA ratio. (Time is inversely proportional to speed, and speed is inversely proportional to square or cube root of CdA. 1.014^3 = 1.04)

Small gains are better than no gains at all, and these gains are not as small and inconsequential as claimed by the math illiterate that frequent the aero threads.


"math illiterate" hahah. How about some common sense? No one's saying there's no difference between aero and non-aero. In a road race, making up that 13 seconds can't be afforded in that large of a time and/or distance. You either make that jump and close the gap or you've lost the wheel and you're done. But good job throwing some numbers out there to validate yourself :thumbup:. Since you like jumping to conclusions, I'll do the same and assume you're not very good at RRs or crits.

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kgt
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by kgt

Sagan got an aero position on his bike. That, yes, it matters. Aero frame... no.

Image

mbrider
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Joined: Fri Mar 12, 2010 10:49 pm

by mbrider

@kgt - thanks for adding your opinion to my post. But you are not suggesting Sagan should show up for a TT with this set up are you? Somehow his superior form right now would make up the difference?

the fact is, Cancellara was not on equal footing. however small an advantage Sagan had throughout the entire race, and in the finale, is debatable. what is not debatable is that Cancellara not having a aero helmet and using mech was at a disadvantage. Would it have made the difference? hard to say. Cancellara and Vanmarcke might have caught Sagan only to lose in the sprint.
If Vanmarcke had not crashed a number of times and actually been able to contribute during the chase, then that would have made a difference. Had Cancellara not sat in the group, and if he would have went with Sagans and Kwio move, that would have made a difference.

But Cancellara found himself in the situation that he did. And the only thing at that moment that would have possibly changed the outcome is better equipment selection. That is what my thread is about.

If you read my responses and what I asked in this post, you would see that I have optimized all other areas. The frame is the last selection.

I have personally done an experiment with my tt bike and set it up with road bars to see if aero does make sense. And it certainly does. Even in a group. When you are traveling at race speeds, it really does matter.

Consider too that the Tarmac in the pic is very similar to a Cervelo S3. Similar in weight (within 50 grams?). Similar in bb and headtube stiffness. Maybe the biggest difference would be in comfort / compliance. But with the S3, you get an aero advantage. And a fairly significant one at that.

Nothing can make up for a significant difference in fitness / form (Kristoff). Aero can sometimes make the difference in specific situations (Kristoff)

justkeepedaling
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Joined: Thu Jan 03, 2008 6:14 am

by justkeepedaling

Gotta love kgt logic with absolutely no data.

Vias/S5/Madone are all faster frames than a Shiv TT. I don't see anyone preaching that TT's should be done on a round tube frame.

Oh wait, people doing road races actually do solo breakaways which is like a TT. And they win races!!!!

But frame doesn't matter.


bm0p700f
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by bm0p700f

Aero gains are not really addtitive though. The saving you get can be predicted but not buy some rule of thumb. You would need ptreety good CFD programme though.

power saved varies with speed and air conditions (drafting). You can say with aero it you will be a little quicker but no one can say by how much. I doubt it would make much difference anyway. If you can ride of from the pack and stay out and win you may gain a few extra seconds from a long break. The thing i if you can ride of from the pack a few seconds is neither here nor there.

If you are in the bunch an aero bike probably does not make much difference. Maybe a little but it is marginal. It certainaly will not allow you to hang on if you are in danger of dropping off and it wont let you win the sprint either. You have to do all that by yourself.

cobrakai
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by cobrakai

bm0p700f wrote:Aero gains are not really addtitive though.

Yes, they are.

bm0p700f wrote:power saved varies with speed and air conditions (drafting).

True.

bm0p700f wrote:If you are in the bunch an aero bike probably does not make much difference.

https://www.cervelo.com/en/engineering- ... he-peloton

bm0p700f wrote:It certainaly will not allow you to hang on if you are in danger of dropping off and it wont let you win the sprint either. You have to do all that by yourself.

https://www.cervelo.com/en/engineering- ... more-metre

I'm certainly not advocating the position that the bike will do all the work for you. But in races where the difference between first and second can be the width of a tire, an aero bike could easily be enough to tip the result one way or the other.

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kgt
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by kgt

Since when Cervelo blog posts are considered as scientific documentation?
Last edited by kgt on Fri Apr 08, 2016 3:56 pm, edited 1 time in total.

justkeepedaling
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by justkeepedaling

Ever since their stated data matches independent windtunnel testing by Cobb and others?

And if you actually read the articles, you'd see there are references...

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kgt
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by kgt

I am referring to the links above. I don't see any documentation.

Ghost234
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by Ghost234

Even at the pro level the effects of aero are not a total game breaker. For years Kittel won sprints on the round tubbed Felt against Cav on his Venge. Sagan has been winning on the Tarmac, not the Venge.

I'm not saying it doesn't help, but it doesn't change the game entirely.


If you are just getting back into racing, don't get a Madone 9. Get an S2/S3. Much cheaper for very similar benefits. You will crash. Unless you are able and willing to eat the cost of replacing a $5000 frame, don't do it.

AJS914
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by AJS914

cobrakai wrote: But in races where the difference between first and second can be the width of a tire, an aero bike could easily be enough to tip the result one way or the other.


How often does that happen in cat 3 or 4?

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Krackor
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by Krackor

cobrakai wrote:
bm0p700f wrote:Aero gains are not really addtitive though.

Yes, they are.

It's actually better than additive. P ∝ CdA*V^2. Improving aerodynamics is essentially "additive" (more like subtractive) in CdA. You improve your body position and lop off 0.02 m^2 CdA. You switch handlebars and get rid of another 0.005 m^2. The lower your total CdA is, the more valuable it is to remove a given amount of CdA since it's a greater percentage difference. This flies in the face of the claims of aero skeptics who say to take care of a couple of the big components then ignore the rest.

I'm not sure I've ever seen any data or math from the aero skeptics around here. It's just unsubstantiated claims with no numbers attached, and complaints when aero proponents' data and math does not live up to the skeptic's arbitrary standards (standards which the skeptic himself does not adhere to).

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