Question to the aero gurus - "non aero" frame vs Cervelo S5 frame / fork / seatpost

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DamonRinard
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by DamonRinard

Remember what question you ask. By the time the answer comes, we're sometimes already thinking of a different question. The answer to the first question is not often the answer to the second question.
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fa63
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by fa63

From what I see, 45-50 W at 40kph is not for just the frame. It is for an aero frame with all the bells and whistles (aero wheels, handlebar, etc.) over a traditional round tubed frame with traditional wheels/handlebar etc. In that context, it seems more plausible.
Last edited by fa63 on Wed Oct 05, 2016 1:44 am, edited 1 time in total.

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by DamonRinard

Bingo.
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ergott
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by ergott

fa63 wrote:From what I see, 45-50 W at 40kph is not for just the frame. It is for an aero frame with all the bells and whistles (aero wheels, handlebar, etc.) over a traditional round tubed frame with traditional wheels/handlebar etc. In that context, it seems more plausible.


This is why I was okay with a Tarmac with aero drop bars, eTap (fewer cables), and some aero wheels.

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by istigatrice

@Calnago I think @RyanH showed a good example, the maths is sound but probably for time constraints (or just lazy) they didn't want to show the full (arguably ugly and tedious) working. I wouldn't go as far to say they're intending to mislead though but people do sometimes take the wrong message from the videos (from my perspective I would argue that isn't Specialized's fault)

cyclespeed wrote:will not save 'proportionally' similar watts, as drag is a function of velocity squared...


I was a bit lose with my use of proportionally (I never said directly proportional or anything along those lines), but you've got the right idea.

@Ergott - don't forget your speedsuit and tyres...
Last edited by istigatrice on Wed Oct 05, 2016 10:54 am, edited 1 time in total.
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Marin
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by Marin

Anyone want to take a guess how close to a "fully integrated" aero bike you could get, say, a Ritchey Logic build - slim steel tubes, especially the head tube?

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cyclespeed
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by cyclespeed

ergott wrote:
fa63 wrote:From what I see, 45-50 W at 40kph is not for just the frame. It is for an aero frame with all the bells and whistles (aero wheels, handlebar, etc.) over a traditional round tubed frame with traditional wheels/handlebar etc. In that context, it seems more plausible.


This is why I was okay with a Tarmac with aero drop bars, eTap (fewer cables), and some aero wheels.


Me too. Exactly what I've done (albeit with Di2).

I've worked extensively on my position and have gone down to a 52 (i.o 54) which drops me 20mm at the front. New, narrower, aero bars. Aero tops, semi-aero helmet.

For me the frame is right at the bottom of my aero list. I love the way the Tarmac handles and feels too much to lose that for an aero frame, and my favourite area is climbing anyway. My 'mental perception' of what I've left on the table due to the frame is about 5W at 40km/h.

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Dr.Dos
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by Dr.Dos

ergott wrote:
fa63 wrote:From what I see, 45-50 W at 40kph is not for just the frame. It is for an aero frame with all the bells and whistles (aero wheels, handlebar, etc.) over a traditional round tubed frame with traditional wheels/handlebar etc. In that context, it seems more plausible.


This is why I was okay with a Tarmac with aero drop bars, eTap (fewer cables), and some aero wheels.

Exactly. It all comes down to how optimized you already are and if costs are an object. So to reiterate what I already mentioned in terms of possible savings, probably in that actual order:

Position (aero vs. power output / distance)
Bodysuit
Handlebar width
Wheels
Helmet
Tires and witdh (resistances vs. grip)
Frame and its integrated components
Handlebar shape
Overshoes
Sock length (no shit)
Everything else

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BeeSeeBee
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by BeeSeeBee

Marin wrote:Anyone want to take a guess how close to a "fully integrated" aero bike you could get, say, a Ritchey Logic build - slim steel tubes, especially the head tube?


Tom Anhalt actually compared a custom aero Stinner he had built to a Vias.
http://bikeblather.blogspot.com/2015/10 ... art-2.html

Another test he did that's a bit relevant to the original topic, he field tested a P2K vs a P3C with the same setup/position, otherwise.
http://bikeblather.blogspot.com/2014/10 ... frame.html

Using the aero rule of thumb: 0.1 lbs (50 g) of drag (@ 30 mph) = 0.5 s/km = 5W = 0.005 m^2 CdA = 0.0005 Crr

That's about 7W (~5W w/ rider) difference between the Stinner and Vias at 0°, and ~23W difference between the P2K and P3C.

I know there's always arguing over aero marketing being overstated, but this stuff does check out in the real world under the right conditions, and you can check it yourself if you're so inclined.
Last edited by BeeSeeBee on Wed Oct 05, 2016 6:54 pm, edited 1 time in total.

Marin
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by Marin

BeeSeeBee wrote:Tom Anhalt actually compared


Cool, hadn't seen these before! Thanks

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fa63
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by fa63

Marin wrote:Anyone want to take a guess how close to a "fully integrated" aero bike you could get, say, a Ritchey Logic build - slim steel tubes, especially the head tube?


Slim steel tubes are not very aero:

http://djconnel.blogspot.com/2014/08/sp ... n.html?m=1

Marin
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by Marin

fa63 wrote:
Marin wrote:Anyone want to take a guess how close to a "fully integrated" aero bike you could get, say, a Ritchey Logic build - slim steel tubes, especially the head tube?


Slim steel tubes are not very aero:

http://djconnel.blogspot.com/2014/08/sp ... n.html?m=1


That's my whole point - the rider position isn't very aero, the build isn't - but the frame? No data there. It's simplifications like this that make the whole discussion so difficult

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fa63
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by fa63

I thought your point was that a bike like Ritchey Logic with "slim steel tubes" would be aero. The post I linked to had a video by Specialized where they tested their aero bike against such a classic steel bike. Their data, from a wind tunnel under controlled conditions, showed the steel frame to have poor aerodynamics relative to the aero frame.

Am I missing something? Sarcasm is hard to catch over the internet sometimes...

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Calnago
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by Calnago

I think the point was that the frame alone is quite insignificant. And that if you were to load up an old skinny round tubed frame with the latest in aero wheels, handlebars, etc., and get yourself in the same aero position then the total difference between the two would be fairly minimal. In that test I think they were using an old Allez, set up as an old Allez, correct? I'd like to see the same test with all the latest aero components such as wheels and bars on the Allez with the same rider position. I suspect the difference would be pretty minimal.


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Marin
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by Marin

fa63 wrote:I thought your point was that a bike like Ritchey Logic with "slim steel tubes" would be aero. The post I linked to had a video by Specialized where they tested their aero bike against such a classic steel bike. Their data, from a wind tunnel under controlled conditions, showed the steel frame to have poor aerodynamics relative to the aero frame.

Am I missing something? Sarcasm is hard to catch over the internet sometimes...


Sorry, I should habe been more specific. Calnago cleared it up already, my question is about the frame's contribution.

My argument is that frontal area does count, so a slim head tube & down tube have less drag than their fat counterparts.
The angled down tube also presents an oval cross section to the already dirty/turbulent air coming from the front wheel, so the loss against an aerofoil/kamm tube wouldn't be that great.

If you take a classic looking frame, put some Zipps with a narrow front tire in it, mount an aero bar with internal cabling, put on etap - how much slower than a full aero frame would it be?

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