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

Back by popular demand, the general all-things Road forum!

Moderator: robbosmans

User avatar
Dr.Dos
Posts: 1073
Joined: Sat Mar 27, 2004 11:00 pm

by Dr.Dos

BRM wrote:A smaller handlebar that doesn't feel right and is a bit uncomfortable, and be honest doesn't really gain speeds . . vs a comfortable handlebar. Make the choice.

When I was racing mountain bikes 20 ys. ago I ran a 44cm handlebar because the transition to training on the road felt easier. Going down to 42 was relatively easy. 40cm took 2hs to get accustomed to. 38cm felt natural right from the start. I had 42cm on last years' winter bike and man, it felt awkward and it felt like that from October to February when I didn't touch any other handlebar width as I run 42 on my CX as well.

My impression is, you have no idea what you are talking about because you a) do not try things out, b) do not have enough use cases and c) you have no imagination about other people's usecases (you might call c) lack of empathy).

User avatar
fa63
Posts: 2533
Joined: Mon Feb 19, 2007 7:26 am
Location: Atlanta, GA, US

by fa63

Here is another data point; the new Colnago Concept aero frame supposedly saves 20W over the C60 at 50 km/h:

http://www.cyclingnews.com/news/colnago ... de-review/

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Ozrider
Posts: 1018
Joined: Sat Nov 20, 2010 6:06 am
Location: Perth, Western Australia

by Ozrider

That's 20W @ 50km/h, how many watts does it save at 30-40km/h where most of us ride?



Sent from my iPhone using Tapatalk
Ozrider - Western Australia
Parlee Z5 XL (6055g/13.32lbs) Trek Madone 5.9 (7052-7500g)Jonesman Columbus Spirit (8680g)
Chase your dreams - it's only impossible until it's done

Marin
Posts: 4035
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Plus "claims to save 20 watts at 50km/h" is code for "we made up a number" - if they had run tunnel tests that showed this, they'd have posted the data.

At 50km/h, your bar tape and front brake cable probably costs 20W.
Last edited by Marin on Tue Oct 04, 2016 1:49 pm, edited 2 times in total.


istigatrice
Posts: 849
Joined: Sat May 12, 2012 8:32 am
Location: Australia

by istigatrice

@Marin did you even read the article. The frame was Wind tunnel tested, but possibly for IP reasons they don't want to post the data.

@Ozrider the wattage saving will be lower but the time saving will be higher at slower speeds. You will still save a similar proportion of watts. Specialized actually have a good video about this.

If you guys aren't interested in aerodynamics why do you feel the need to post on these threads? You're not adding any value, I don't have a problem with 'that design doesn't look aero for reasons a, b, c' but what's the value in blind skepticism like 'oh they just made up a number'?
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

Marin
Posts: 4035
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

istigatrice wrote:but possibly for IP reasons they don't want to post the data.


Yes, I read the article. Why IP reasons if they are only claiming improvements against their own product?

I'm _very_ interested in aerodynamics, which I why follow most threads about the topic and try to form my own opinion.


Currently, my opinion is that bike aerodynamics don't matter a lot and are highly overvalued compared to riding position and kit aero for obvious marketing reasons. I'm actually still pretty shaken that Mr. Rinard claims a 50w saving for an aero bike since he's one of the few sources I tend to beleive.

thumper88
Posts: 176
Joined: Tue Mar 13, 2012 7:27 pm

by thumper88

Damon has the best information, I'd go with his number for that speed.
But of course there is a seemingly infinite range given the variables... speed, wheel choice and how it interacts with frame, whether you go with the Cervelo bars. How wide the bars are is an all but unexamined biggie.
I ride that exact bike and do not possess a wind tunnel, but I can tell you that the difference is enough for this relatively unsophisticated piece of pack fodder to feel versus a Tarmac or say Allez DSW.
On a downhill I ride every ride and have done hundreds of times on at least 8 bikes, it's clear that its worth somewhere between 1.5 and 2.2 mph at @34 mph.
If i'm on the front, and the person on second wheel has an ftp that's say 40 watts lower, the result can be pretty hard on them. If their FTP is close or more, of course no biggie.

User avatar
cyclespeed
Posts: 1112
Joined: Mon Jun 06, 2016 8:45 am

by cyclespeed

istigatrice wrote:@Ozrider the wattage saving will be lower but the time saving will be higher at slower speeds. You will still save a similar proportion of watts. Specialized actually have a good video about this.


Not correct. You will not save 'proportionally' similar watts, as drag is a function of velocity squared. So the watts saved at 40kph will be significantly lower than at 50.

A quick back of a fag packet calculation gives me less than 13 watts at 40km/h, and even that I'd take with a hefty pinch of salt.

User avatar
Calnago
In Memoriam
Posts: 8612
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

That video by Specialized that @istigatrice is referring to is one of the most laughable and arguably misinterpreted (to their benefit of course) videos that I think they've done. That whole "slower riders will save even more time" bs is ridiculous. They don't do the math but rather say something like "we'll leave that to the mathletes out there". Think the scenario through at the extremes (like going extremely slow to the point you might fall off your bike) and you can start to see how ridiculous it is, unless you believe that aero matters at 2mph. But amazingly enough there are people that will argue with a straight face that aero does indeed come into play at super slow speeds. Whether it's measurable or not is another matter.


Sent from my iPhone using Tapatalk Pro
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

RyanH
Moderator
Posts: 3181
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

@Calnago the math is pretty straight forward and there's calculators for that, no need to go into a Reductio ad absurdum argument. When looking at RAAM or even Iron Man's where average speeds can be 16 to 20 mph, the time saved in absolute terms is a large number for going to an aero bike (in these cases, we're talking TT position on a TT bike).

If we have two scenarios where Rider A and B are choosing between a road bike @ 0.3 CdA and a TT bike at 0.25 CdA. Rider A expects to average 120w for the bike leg of the IM, and Rider B plans to average 260 watts, everything else is identical about them:

Estimated speeds:
Rider Watts 0.3 0.25
Rider A 120 28.4 30.0
Rider B 260 38.2 40.4

Estimated Time (Hours)
Rider 0.3 0.25
Rider A 5.66 5.36
Rider B 4.22 3.98

Time Difference (seconds)
Rider A: 1086.0
Rider B: 844.5


Here's a good calculator:

http://www.cyclingpowerlab.com/PowerSpeedScenarios.aspx

User avatar
Calnago
In Memoriam
Posts: 8612
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

Fair enough @RyanH... at 16-20mph I get that, it's in a range where it can help. It's when people start arguing that there's a benefit no matter how slow you're going that is nebulous. Even in the video they state something like "in the speed range we're talking about" or something like that, but they don't state what that range is. So then you get people trying to argue the benefits even if they're going 5mph, which is exactly what Specialized would like the masses to take away from that video. Those are the kinds of arguments I'm referring to when I say the video is being "misinterpreted".
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

RyanH
Moderator
Posts: 3181
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

Who rides bikes at less than 16 mph? :noidea: Haha.

thumper88
Posts: 176
Joined: Tue Mar 13, 2012 7:27 pm

by thumper88

If I were riding 16 to 20 on normal group rides I wouldn't bother with the aero bike, as much as a love mine. And for sure not 16 to 18.
RAAM is not particularly useful except for a pure lab-like number in this case.... its an extremely unusual case. But OK, fair enough.
But Damon put the thing in the tunnel.

RyanH
Moderator
Posts: 3181
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

DamonRinard wrote:
mbrider wrote:Specialized Tarmac SL4 with standard handbuilt clinchers 28/32 spokes / regular round bar / cables in the wind / standard brakes sticking out / regular pedals.

What would be the aero advantage of a Cervelo S5 with all the aero do dads (zipp 404s ~ 10 watt / Cervelo aero bar ~ 6 watt / SRAM Etap ~ 6 watt / TriRig front brake / EE rear brake ~ 2- 3 watt combined / aero pedals ~ 2 watt)

Would the aero advantage be 45 watts over the Specialized? 50 watts?

Lets keep this as a discussion about the bikes and not about position. Assume the same position can be achieved on either bike.


Yes, 45 to 50 Watts at 40 km/h is about right. Knock off about 1/3 if you're drafting.


@thumper88, Damon was ballparking 45-50w (see above). The only tunnel backed number he provided (that I saw) was 25w @ 40kph on the first page.

My preliminary testing is putting me on the hoods on the Litespeed T3 (38cm Ergonova bars, Campy SR, 165 cranks, 404s, longer reach than before and more drop) at a CdA hovering around 0.30 or just slightly under. To improve 50 watts over my setup would put my CdA around 0.24...that's good TT setup territory. Granted, I have 404s which are good for what, 8w @ 40kph? Still, that's 0.25 CdA which my gut check says no, I'm not going to achieve 0.25 CdA on a road bike on the hoods (although, kWalker would disagree).

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Post Reply