*Tour Aero Bike Test 2019*

Discuss light weight issues concerning road bikes & parts.
robeambro
Posts: 611
Joined: Sat Jul 07, 2018 6:21 pm

by robeambro

AJS914 wrote:
Mon May 13, 2019 2:21 pm
robeambro wrote:
Mon May 13, 2019 8:27 am
I'm not saying aero frames aren't good for sprinting, just that since it's a very short-timed event, the difference they make is often overshadowed by much other important factors. Unlike in crits, where arguably you gain for hours an aero benefit.
Aero benefits are not overshadowed. Aero benefits are always available. I just don't get the constant minimizing of aero benefits.

From the System Six white paper:
Consider the final kick with
the final 200m covered at an average speed of 60 km/h.
For a typical rider that 12s effort would require an average
of 1000W. Over this final kick the SystemSix would achieve
a 2.1 km/h top speed and reach the line 0.4 sec ahead of
the modern race bike. That doesn’t sound like a big margin,
but at 60km/h that equates to 7.2m, or four bike lengths.
https://www.cannondale.com/~/media/File ... epaper.pdf

If you don't believe their marketing numbers then go plug in your own numbers in the analytical cycling site.
I don't mean to be a smartass, also cause English isn't my first language, but "to overshadow" doesn't mean that something is not available, just that there are far more important aspects.

That said, the Cannondale White Paper compares "a modern race bike", which is either the SS Evo or a whatever-round-tube frame, I assume. So clearly the aero benefits are amplified to sound better for marketing. Let's just do it ourselves, shall we.

If you watch this video, at the specified time you'll see a table with average CdA's in the drops and in an aero position on the hoods, which is not really like sprinting but hey ho: https://www.youtube.com/watch?v=gWDmbKzf3ig&t=262s

You'll see that in the "Straight Arms Drops" position, the Cda for the Tarmac is 0.3091, and for the Reacto is 0.2973.

So, let's go to this website and plug all the data in: http://www.aeroweenie.com/calc.html

Well, on a sprint @1000w, the terminal speed for the Reacto is 61.96kmh, while for the Tarmac is 61.18. A difference of roughly 0.78kmh, which is meaningful, but only a bit more than ONE THIRD of what Cannondale claims. So maybe one third of four bike lengths, which is 2.4 metres in those 200m.

Oh and this is for that level of sprinting, not sure how many can hold that power. For lower level cat 6959 sprinters, may be less than that. If we do the same @ 900w, the difference in speed becomes 58.99 vs vs 59.25, which is 0.26kmh, which is some odd 20 watts, so still meaningful, nothing to be sniffed at, but it's still a bit more than ONE TENTH of what Cannondale claims. .

Is there a difference? YES. The aero bike is better for sprinting.
Is it as big as Cannondale claims if you compare a decently aero frame like the Tarmac? NO WAY.

I don't mean to deny aero. I think the data is pretty clear. I just wish you'd convene with me that the difference FOR THE FRAME isn't very big and in most cases isn't worthwhile buying into, and definitely not because of what the marketing says.

And this is sprinting at high watts, don't get me started on how beneficial an aero frame is on a mixed course..
Last edited by robeambro on Tue May 14, 2019 8:34 am, edited 1 time in total.

by Weenie


AJS914
Posts: 3465
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Cannondale is comparing to their super six evo climbing bike. The current Tarmac is basically an aero bike when you add the deep wheels and an aero handebar - trying to say the Venge isn't worth it because the Tarmac is so close is splitting hairs.
I don't mean to deny aero. I just wish you'd convene with me that the difference FOR THE FRAME isn't very big and in most cases isn't worthwhile buying into.
I 100% agree. Running out and buying a whole new aero frame just to save 10 or 15 watts isn't worth it for the vast majority of riders.

robeambro
Posts: 611
Joined: Sat Jul 07, 2018 6:21 pm

by robeambro

AJS914 wrote:
Mon May 13, 2019 3:50 pm
Cannondale is comparing to their super six evo climbing bike. The current Tarmac is basically an aero bike when you add the deep wheels and an aero handebar - trying to say the Venge isn't worth it because the Tarmac is so close is splitting hairs.
I don't mean to deny aero. I just wish you'd convene with me that the difference FOR THE FRAME isn't very big and in most cases isn't worthwhile buying into.
I 100% agree. Running out and buying a whole new aero frame just to save 10 or 15 watts isn't worth it for the vast majority of riders.
Oh yeah and the Tarmac tested as above did not have an aero handlebar, just saying. So maybe my above calculations would see it fare even better.

I understand that it is splitting hairs, but all of the new gen "lightweight" bikes will have aero content, while the current crop of aero bikes tends to be slower than previous gen due to discs. So the "gap" isn't getting any bigger, and comparing "Tarmacs" vs aero bikes is going to be the norm, while comparing "SS Evo's" to aero bikes will be fairly anachronistic.

RocketRacing
Posts: 869
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

Lots of math.

Lets take 3lbs off a 15lbs bike. That is a 20% weight reduction. Nice! Lets call that our climbing bike.

For a 60kg rider, that is about a 2% total reduction in system weight. For a 90kg rider, it is closer to 1.5% reduction. So light bikes pay more dividents to the lighter rider... but they are still small numbers.

Weight has little to do with performance on the flat, that is down mostly to aero and power. On the climbs, power to weight rules. The steeper the climb, the more benefit you get (and the slower you go, so the less aero matters). The crossover point of weight vs aero varies... but a rough number is a 4% incline where weight gains begin to surpass aero.

Lets look at a 75kg rider. 3lbs off the bike is worth very little at a 0% incline. Sorry folks. At a 2% incline, 3lbs is worth about 2.5w (in rolling resistance) That is like upgrading your gp4000s2 to Gp5000. At 10% average grade, that weight weenie bike is now worth about 7.5w. That is like the difference between gp5000 and much slower conti 4 seasons. So about 2.5w per lbs at a 10 degree incline.

Aero gains are more the faster you go. The steeper the climb, the more you slow, the less aero gains help.
Weight losses help with greater incline.

So, if you have to chose aero vs light... light wins as the average incline increases. And vice versa.

However... if you are more aero on a climb, and there is a headwind, the aero bike will be slowed less.

So heavier riders/sprinters probably have more to gain from an aero bike. Lighter riders will gain more from a lighter bike than will a heavy rider... but only when climbing.

My advice it to chose a bike that plays to your goals/strengths. I like what was said above that pros choose the bike that will perform best in the part of they race that they plan to attack.

spdntrxi
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Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

I thought the tipping point was closer to 6%... but otherwise I agree.

TobinHatesYou
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by TobinHatesYou

spdntrxi wrote:
Mon May 13, 2019 10:28 pm
I thought the tipping point was closer to 6%... but otherwise I agree.

The tipping points are based on speed. A 150lb rider going up a 6% grade at 400W is going 15mph and is certainly benefitting aerodynamically. At 8%, they are going >12mph and probably breaking even vs a bike that is 2lbs lighter.

Let's say there's a really short 12% ramp that takes 30s at 700W... The rider is moving at 14.5mph and the aero bike is likely faster.

For us mortals, 6% at 300W is still 12mph. My times up such climbs are basically the same on my Madone and Emonda. 30min on 6%? Probably bringing the Madone. 60min? Probably bringing the Emonda.
Last edited by TobinHatesYou on Tue May 14, 2019 12:10 am, edited 1 time in total.

cajer
Posts: 201
Joined: Sun Jul 14, 2013 1:26 am

by cajer

Has anyone ridden both the Madone SLR and Cervelo S5 Disc? I’m debating between the two, though I’m looking at the rim Madone.

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Calnago
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by Calnago

@cajer: I’ve ridden the rim brake Madone. And if you’ve been around here for any kind of time at all you likely know I’m not the world’s biggest fan of disc brakes on high end road race bikes. However, I do insist on good braking, regardless of whether it’s rim or disc and have to say I felt the Madone’s brakes are not up to a standard I can appreciate any more than a “meh, they work, sorta” kinda way. As such I’d say go disc brake if you go with the Madone.
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
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by RyanH

TobinHatesYou wrote:
Mon May 13, 2019 11:53 pm
The tipping points are based on speed. A 150lb rider going up a 6% grade at 400W is going 15mph and is certainly benefitting aerodynamically. At 8%, they are going >12mph and probably breaking even vs a bike that is 2lbs lighter.

Let's say there's a really short 12% ramp that takes 30s at 700W... The rider is moving at 14.5mph and the aero bike is likely faster.

For us mortals...
That basically describes our Sunday ride (6% grade at 400w, false flat, then 700w for 30s):

https://www.strava.com/activities/17047 ... /5337/5965

I've ran the numbers before when I had the Wilier Cento10Air and despite it being 7.3kg, it was faster (at least on paper) than my 5.5kg focus for that entire route at those speeds.

AJS914
Posts: 3465
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

What about a lighter, smaller rider with a smaller FTP vs. larger rider?

One thing I was thinking that on the flats, an aero bike is going to benefit the smaller rider more than the bigger more powerful rider.

Hypothetical riders:
54kg 170 watt ftp 3.14 watts per kg
88kg 275 watt FTP 3.13 watts per kg

Hypothetical aero bike savings: 25 watts (probably higher at key points of a ride/race)

As a percentage of FTP, the smaller rider is saving 15% of their FTP power and the larger rider only 9%.

RocketRacing
Posts: 869
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

4% is an estimate. The “why” is described well above. Basically, the stronger you are, the faster you go. The faster you go, the higher the average grade required before the light bike starts to outperform the aero bike.

A similar relationship goes for rider weight. Lighter riders will find advantages in the lighter bike at sliggtly lower grades than a heavier rider.

The answer for “what upgrades are fastest” likely comes down to the course, but i do not think you can go wrong doing the following: go aero with you forward most facing components, and spokes. So bars, fork, front brake, rims, narrower front tire. Frame helps also, but is less bang per $. Everything else, go as light as possible.

TobinHatesYou
Posts: 4163
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RyanH wrote:
Tue May 14, 2019 3:02 am
TobinHatesYou wrote:
Mon May 13, 2019 11:53 pm
The tipping points are based on speed. A 150lb rider going up a 6% grade at 400W is going 15mph and is certainly benefitting aerodynamically. At 8%, they are going >12mph and probably breaking even vs a bike that is 2lbs lighter.

Let's say there's a really short 12% ramp that takes 30s at 700W... The rider is moving at 14.5mph and the aero bike is likely faster.

For us mortals...
That basically describes our Sunday ride (6% grade at 400w, false flat, then 700w for 30s):

https://www.strava.com/activities/17047 ... /5337/5965

I've ran the numbers before when I had the Wilier Cento10Air and despite it being 7.3kg, it was faster (at least on paper) than my 5.5kg focus for that entire route at those speeds.

Haha, wow, that ride really is weirdly appropriate to the discussion.

RyanH
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by RyanH

AJS914 wrote:
Tue May 14, 2019 3:09 am
What about a lighter, smaller rider with a smaller FTP vs. larger rider?

One thing I was thinking that on the flats, an aero bike is going to benefit the smaller rider more than the bigger more powerful rider.

Hypothetical riders:
54kg 170 watt ftp 3.14 watts per kg
88kg 275 watt FTP 3.13 watts per kg

Hypothetical aero bike savings: 25 watts (probably higher at key points of a ride/race)

As a percentage of FTP, the smaller rider is saving 15% of their FTP power and the larger rider only 9%.
The more aerodynamically optimized you are (or smaller you are), the more significant the savings. Off the top of my head, an aero frame/wheels generally means a 0.02 CdA difference. If you're super aero and ride around with a 0.26 CdA with a non aero setup, then you'd be as low as 0.24, representing an 7.7% benefit vs an upright, larger rider that may be 0.35 CdA getting reduced down to 0.33 which is a 5.8% benefit.

TobinHatesYou
Posts: 4163
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RyanH wrote:
Tue May 14, 2019 3:23 am

The more aerodynamically optimized you are (or smaller you are), the more significant the savings. Off the top of my head, an aero frame/wheels generally means a 0.02 CdA difference. If you're super aero and ride around with a 0.26 CdA with a non aero setup, then you'd be as low as 0.24, representing an 7.7% benefit vs an upright, larger rider that may be 0.35 CdA getting reduced down to 0.33 which is a 5.8% benefit.

But then again we’re taking about riders that are several mph apart and the larger, faster rider is in fact saving more watts if he’s moving at 24mph vs the smaller rider moving at 21mph. The smaller rider is, however, saving more seconds over the same distance. Just a matter of perspective I guess.

RocketRacing
Posts: 869
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

AJS914 wrote:
Tue May 14, 2019 3:09 am
What about a lighter, smaller rider with a smaller FTP vs. larger rider?

One thing I was thinking that on the flats, an aero bike is going to benefit the smaller rider more than the bigger more powerful rider.

Hypothetical riders:
54kg 170 watt ftp 3.14 watts per kg
88kg 275 watt FTP 3.13 watts per kg

Hypothetical aero bike savings: 25 watts (probably higher at key points of a ride/race)

As a percentage of FTP, the smaller rider is saving 15% of their FTP power and the larger rider only 9%.
Bike calculator .com will help visualize the difference. Assuming the same bike/clothes/cda, the larger rider should still have a larger surface area, so more drag. So to go the same speed, the larger rider will need to put out more power. But the difference will not be huge, at least not as much as the power differential.

On the flat, drag and max average power dominate. W/kg is not as relevant, simply because mass has far less influence. This is why sprinters are all heavier, more powerful riders. This is also why w/kg is more important for climbs... and the steeper the climb, the more w/kg becomes key. In a climb, gravity makes itself heard far louder.

There is an interesting article on zwift insider that was just released on pacing the giro stage 1 tt. Basically, half your time is spent on flat, half spend on a near 10% grade. People go faster when they pace under ftp on the flat (saving energy), and over ftp on the climb. So “work hardest when you are slowest.”

Why? Because going faster requires exponentially more work as you hit very quick speeds due to the mathmatical nature of drag. So for a 10% increase in power, you might only see a 5% increase in speed on the flat section.

Increase your power by 10% on the climb, and your speed will increase closer to 9.5%. You can save near a minute by going sub ftp on the flats, and over ftp on the climb vs a steady even ftp the entire stage.

But... the slower you are, the more seconds you save with an aero bike.... mainly because you are on the track longer. But you still loose.

by Weenie


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