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PostPosted: Thu Feb 20, 2014 10:45 pm 
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Joined: Tue Jul 18, 2006 5:18 am
Posts: 584
Location: Cambridge, New Zealand
I do a lot of modelling using wind tunnel data, factoring course elevation/direction, equipment weight and rider metrics. I have had very good success relating the models to the real world.

For TT/Tri I look at steady state, solo scenarios (though do have different drafting factors for Tri as cheating is prevalent). For road races I analyse the pinch points - much as I do when coaching athletes - it's all about getting up the crucial hill or having a kick at the finish. Tour have gone with the Tri/TT method (though have alluded to the pinch point effect with cav/goss).

I may have some time later to work with Tours numbers to turn them into more useful info, in the meantime - I wrote this article http://speedtheory.co.nz/tour-de-france ... nt-effect/ about Bakelants stage winning effort - 10m difference over 1.6km on his own (at 53kph) by using an aero advantaged road frame - not enough to mean that he would have lost without - but enough to mean that he wouldn't have had yellow. Which turns it into a very significant difference.

I've analysed a few MAMIL favoured fun rides and the differences in energy usage by having an aero frame in a peloton at 30kph are not huge. But they are there. My personal experience is that riding an aero frame feels like cheating, but it's legal! So why wouldn't I do it?

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Posted: Thu Feb 20, 2014 10:45 pm 


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PostPosted: Tue Feb 25, 2014 3:52 pm 
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Joined: Fri Aug 23, 2013 7:39 pm
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I totally agree with tommasini. Just a few percent over 4 hours+ for us mere mortals isn't going to matter. So #aeroiseverything = not if your not a pro. Come to think of it, having a nicely fitted jersey is probably going to matter more.


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PostPosted: Tue Feb 25, 2014 4:37 pm 
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Joined: Mon May 30, 2005 7:13 am
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mdusink, but what if you wore a well fitting jersey and had an aero frame? why do small margins not matter to cat 4-5 racers, don't crits come down to small margins? Do people like to win less just because its not their job? If you're going to pay $2500-10000 for a new bike, why not get something on the more aero side?

Lets face it, the new S2/S3, AR and Propel advanced all have frameset weights that are not a hinderance, and are a step up in comfort and stiffness over older aero models. Benefit, with little compromise.


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PostPosted: Tue Feb 25, 2014 5:13 pm 
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I'm surprised by the closeness of the results. I wish they were able to model using a full body mannequin. SI can see a 1-2kmh increase in speed with no increase in power just by rotating my hips forward and bending my elbows a few more degrees. If I leave that position and go onto the hoods, Id be going 4-5kmh slower. I find it hard to believe that my torso position does not affect the aerodynamics of the frame and of the entire mass of me and the bike.

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PostPosted: Tue Feb 25, 2014 5:33 pm 
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Joined: Fri Jan 07, 2011 6:58 am
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Location: 604
Will never buy a cervelo because of rubbish white paper marketin.... errrr I mean data like this. Can't decide if the significance cervelo gives to these results is laughable or insulting our intelligence.


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PostPosted: Tue Feb 25, 2014 5:41 pm 
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Joined: Wed Jan 01, 2014 8:33 pm
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petepeterson wrote:
Will never buy a cervelo because of rubbish white paper marketin.... errrr I mean data like this. Can't decide if the significance cervelo gives to these results is laughable or insulting our intelligence.
http://www.tealsport.com/_upload/showca ... esults.pdf Cross Giant off your list as well. http://www.specialized.com/OA_MEDIA/pdf/Witchcraft.pdf And Specialized.


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PostPosted: Tue Feb 25, 2014 5:44 pm 
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That is not a white paper by Cervelo, it is just the results from a recent Tour magazine test. So don't blame Cervelo for just sharing the results from a test where their bikes came out on top.

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PostPosted: Tue Feb 25, 2014 5:46 pm 
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743power wrote:
I'm surprised by the closeness of the results. I wish they were able to model using a full body mannequin. SI can see a 1-2kmh increase in speed with no increase in power just by rotating my hips forward and bending my elbows a few more degrees. If I leave that position and go onto the hoods, Id be going 4-5kmh slower. I find it hard to believe that my torso position does not affect the aerodynamics of the frame and of the entire mass of me and the bike.


I thought it was mentioned earlier that they indeed used a pedaling mannequin for the test?

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PostPosted: Tue Feb 25, 2014 7:00 pm 
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Joined: Fri Aug 31, 2012 6:32 pm
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I think it's funny that so many people here are poopoo-ing a 1% difference between the fastest and slowest frames yet these are the same people who came to this website to save 20g on their saddle. 20g for a light rider with a light bike is only a 0.3% difference up a completely vertical wall.


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PostPosted: Tue Feb 25, 2014 8:08 pm 
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fa63 wrote:
I thought it was mentioned earlier that they indeed used a pedaling mannequin for the test?


They only used the bottom half of the dummy.

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PostPosted: Wed Feb 26, 2014 2:59 am 
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Location: Toronto, Canada
Also all but the giant propel got a zipp vuka sprint bar. This skewed the results as the giant bar is not as aero but is lighter and stiffer. It also hurts less as the rear of the vuka is so sharp if you hit the top of your arm when in the drops you will bruise.


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PostPosted: Wed Feb 26, 2014 3:48 am 
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deek wrote:
I think it's funny that so many people here are poopoo-ing a 1% difference between the fastest and slowest frames yet these are the same people who came to this website to save 20g on their saddle. 20g for a light rider with a light bike is only a 0.3% difference up a completely vertical wall.

HA. True.
However: I assume you've used a 6kg bike and a 60kg rider, so is it then 0.03%? I'm no scienticianist :thumbup:


Last edited by User Name on Wed Feb 26, 2014 4:43 am, edited 1 time in total.

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PostPosted: Wed Feb 26, 2014 4:11 am 
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Joined: Wed Jan 01, 2014 1:40 am
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An aero bike is as aero as an aero bike can be but a person can only be so aero, quintessentially an aero bike is more aero than a person, therefore who would care if a test dummy is utilised in aero testing or not, that is of course unless an aero test dummy was used then one would be quite interested.


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PostPosted: Wed Feb 26, 2014 4:24 am 
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Location: Geeeelong! / YURP
mdusink wrote:
So #aeroiseverything = not if your not a pro.

On that reference, Spec's data shows that the difference between a 'bad' helmet (eg: the Prevail) and an aero helmet (eg: the Evade) is not as pronounced for a rider with a low and aero position.

Whereas a rider (read: "if you're not a pro") with a more upright position will actually have a greater benefit. NGNM nailed it, it's a marginal gain that is up to each individual as to whether they buy in to.

Otherwise, deek. Word! :beerchug:

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PostPosted: Wed Feb 26, 2014 1:32 pm 
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Joined: Fri Aug 27, 2010 4:22 pm
Posts: 80
I think my main concern with NGNM's argument of 'why not' is that's it's not the simple choice of an identical frame with Y/N aero or not. There is usually a penalty in either harshness of ride or (certainly on older aero frames) front end stiffness.

I'd rather ask 'why give up ride quality for a gain that's so small it's barely measurable?'. That said, each to their own and aero frames have improved a lot so the penalty is shrinking.

Deek, damn you for pointing out the obvious! :D


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Posted: Wed Feb 26, 2014 1:32 pm 


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