"Lightness" vs "Aeroness"

Discuss light weight issues concerning road bikes & parts.
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iflyadesk
Posts: 136
Joined: Thu Oct 11, 2012 2:18 am
Location: Chicago, IL

by iflyadesk

When I saw this from Specialized selling the Tarmac SL7, it was really persuasive because it nailed exactly what I love about my Canyon Aeroad. Most aero bikes are too heavy (and stiff) and most light bikes don't care enough about aero. I thought of the Canyon Aeroad as the only "middle ground" bike available on the market. What Specialized implies with this chart is the new Tarmac SL7 is not a "middle ground" but a "best of both worlds" and oh my goodness was it hard for me not to click BUY NOW!


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Of course, $12k (+ 10% tax) is a lot of money, so it forced me to use my cerebral cortex instead of just my limbic system. As an engineer, I'm always suspicious of dimensonless charts. But they are making claims that can be backed by numbers we have (thanks to Tour Magazine). So, I created my own "aeroness vs lightness" chart for bikes that I could find Tour Mag data. It's only as good as the data, and it doesn't take things like seat post stiffness into consideration (which I find very important -> hated my 2016 Giant Propel because it beat the hell out of me), but it's something to look at and chat about regardless.

AUG 18, 2020 EDIT: Added rim brake bikes, a guess at model years, fixed some errors, removed the link to Google Sheets because Excel is so much better at labeling and breaking out series.

AUG 23, 2020 EDIT: I think one way to better capture the "right tradeoffs" is to make the slope of the lines on the chart match the equivalent lightness vs aeroness based on a model.

AUG 27, 2020 EDIT: I just realized the original chart from Specialized included the Venge Vias and 1st Gen Venge but my chart did not, so I figured I should add them for completeness.

I was not a Tour Mag reader in Feb 2015 so I totally missed this explanation of their model and how they determine tradeoff between light and aero:


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So roughly translating that model to my chart, I've added one set of lines to show a 100km race with 500m of elevation (~270g per W) and another set of lines to show a 100km race with 2000m of elevation (~70g per W). They are assuming 85kg for the rider, bike, and kit. My personal calculations in this thread trying to figure out the weight-to-aero tradeoff for multiple accelerations in a flat crit were roughly 100g per W so that falls in between these two. I think maybe these are solid "bounding conditions." The tradeoff between lightness and aeroness likely falls on or between these two slopes for any given race.

As you can see, the 2015 Venge and Venge Vias (both rim and disc) do not really fall at the same places on my chart based on Tour Mag data. "Aeroness" could be slightly different based on differences in testing protocols between Tour and Specialized but weight is pretty straightforward. It's amazing that in 2015 you could get a top-of-the-line 6.7kg S-Works Venge for 7300 EUR. My, how times have changed. It would seem to me that bikes really haven't gotten lighter or more aero in the last six model years. What they (as an industry) have done is managed to stay pretty close to the "lightness vs aeroness efficient frontier" while providing us with better ride quality, disc brakes, electronic shifting, and easier serviceability.

SEP 2, 2020 EDIT:
Updates include:
• a couple new bikes
• several fixes of "fat finger errors" on my part
• align all the year make and model labels on the edges of the chart
• made rim brake dot looks like a rim, disc brake dot looks like a disc — pretty proud of myself for that idea, lol
• updated "Watts at 45kph" to include the air resistance of upper body and rolling resistance of tires to give a more realistic representation of the percent marginal gains at play here
• made the lines for 500m and 2000m climbining in 100km represent time-to-complete for 75kg rider at 200W average
• removed 2021 Trek Madone SLR because it was Mad Petersen's personal bike, a size 58cm with 28mm front tire and different handlebars... all things that make it unfairly slower and heavier than every other bike tested and was causing confusion


SEP 27, 2020 EDIT:

Added more bikes

Image


P.S. there are a ton more bikes out there that Tour Mag has tested that I haven't included. If there's one you know they've tested you'd like to see represented on this chart, please let me know and I'll add it. And please do buy the article from them covering the bike you want to see online or in their app. A $3.99 service that helps you make a $6,000-$12,000 decision is totally worth it. Plus, if we don't all continue to support them, there won't be anyone out there to help us seperate marketing from science.
Last edited by iflyadesk on Mon Sep 28, 2020 1:32 am, edited 11 times in total.
2018 Canyon Aeroad Disc - 7.1kg | 2018 Specialized Crux - 8.0kg

Retired: 2015 Giant Propel Advanced SL - 7.0kg | 2018 Santa Cruz Stigmata - 6.8kg | 2018 Trek Madone 9.0 - 7.1kg | Switch Single Speed - 5.9kg

ichobi
Posts: 1187
Joined: Thu Jan 19, 2012 11:30 pm

by ichobi

Whats that Canyon aeroad with tarmac wheelset?

by Weenie


alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Don't forget that shoecovers are worth more in watts saved than aero frame vs climbing frame.

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

by robeambro

There's one inherent flaw in this chart. Each tick on the aero axis is worth 6 watts, whilst each tick on the weight axis is worth 300g. Whilst the former is admittedly not much, is still far more important than a mere 300g (other than for our egos..).

This means that the chart makes you think that bikes in the top right corner are faster, whereas it's probably most of the aero bikes that are faster everywhere.

A possible solution would be to make the x and y axis to have the same dimension (ie watts) by converting the gram saving into watt savings at a certain power, so that the chart becomes "faster up a 8% climb" vs "faster on the flats". Or, by converting the watts into time saved, so that the chart becomes "time saved over a 5km, 8% climb" vs "time saved over a 10km flat TT".

pmprego
Posts: 583
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

I continue to find the aeroad tour results weird. It means that any manufacturer wasn't able to beat a bike that is now several years old.

Canyon has some type of holy grail of intelligence. Sorry but that is not likely. Actually, it's probably not true as canyon is not likely to have more R&D than firms like specialized or cannondale or giant that have way bigger budgets.

Steve Curtis
Posts: 346
Joined: Thu Jul 31, 2008 12:20 pm
Location: Hampshire UK, Dublin Ireland and Geneva Switzerland.

by Steve Curtis

alcatraz wrote:
Sat Aug 15, 2020 6:34 am
Don't forget that shoecovers are worth more in watts saved than aero frame vs climbing frame.
Exactly this. The frame is such a small part of the overall aero equation.
Ride what you want with shoe covers and save yourself the indignity of riding an SL7

Stueys
Posts: 470
Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

pmprego wrote:
Sat Aug 15, 2020 7:39 am
I continue to find the aeroad tour results weird. It means that any manufacturer wasn't able to beat a bike that is now several years old.

Canyon has some type of holy grail of intelligence. Sorry but that is not likely. Actually, it's probably not true as canyon is not likely to have more R&D than firms like specialized or cannondale or giant that have way bigger budgets.
Aeroad is a great design no doubt but lots of people have noticed that German brands tend to do consistently well in Tour tests

alanyu
Posts: 570
Joined: Thu Jun 06, 2019 1:10 pm

by alanyu

IIRC, tarmac sl6 is 220W with CLX50

demoCRIT
Posts: 99
Joined: Sat Jun 01, 2019 3:04 pm

by demoCRIT

sooooooooooo
people will belive "6% better" with 0 data to back it up
but anything with an actuall data to back it up won't be taken seriously because "reason 1/2/3"

yea

pmprego
Posts: 583
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

demoCRIT wrote:
Sat Aug 15, 2020 10:05 am
sooooooooooo
people will belive "6% better" with 0 data to back it up
but anything with an actuall data to back it up won't be taken seriously because "reason 1/2/3"

yea
Which side are you referring to?

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iflyadesk
Posts: 136
Joined: Thu Oct 11, 2012 2:18 am
Location: Chicago, IL

by iflyadesk

ichobi wrote:Whats that Canyon aeroad with tarmac wheelset?
That’s me hoping I can just swap the 1610g DT Swiss wheels on the Canyon for the 1410g Roval Rapide wheels of the Tarmac and save 200g without losing aero, thereby making my 3yr old bike “near enough as makes no difference.”
2018 Canyon Aeroad Disc - 7.1kg | 2018 Specialized Crux - 8.0kg

Retired: 2015 Giant Propel Advanced SL - 7.0kg | 2018 Santa Cruz Stigmata - 6.8kg | 2018 Trek Madone 9.0 - 7.1kg | Switch Single Speed - 5.9kg

User avatar
iflyadesk
Posts: 136
Joined: Thu Oct 11, 2012 2:18 am
Location: Chicago, IL

by iflyadesk

alcatraz wrote:Don't forget that shoecovers are worth more in watts saved than aero frame vs climbing frame.
Are you allowed to wear shoe covers when riding a more aero frame?


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2018 Canyon Aeroad Disc - 7.1kg | 2018 Specialized Crux - 8.0kg

Retired: 2015 Giant Propel Advanced SL - 7.0kg | 2018 Santa Cruz Stigmata - 6.8kg | 2018 Trek Madone 9.0 - 7.1kg | Switch Single Speed - 5.9kg

User avatar
iflyadesk
Posts: 136
Joined: Thu Oct 11, 2012 2:18 am
Location: Chicago, IL

by iflyadesk

robeambro wrote:There's one inherent flaw in this chart. Each tick on the aero axis is worth 6 watts, whilst each tick on the weight axis is worth 300g. Whilst the former is admittedly not much, is still far more important than a mere 300g (other than for our egos..).

This means that the chart makes you think that bikes in the top right corner are faster, whereas it's probably most of the aero bikes that are faster everywhere.

A possible solution would be to make the x and y axis to have the same dimension (ie watts) by converting the gram saving into watt savings at a certain power, so that the chart becomes "faster up a 8% climb" vs "faster on the flats". Or, by converting the watts into time saved, so that the chart becomes "time saved over a 5km, 8% climb" vs "time saved over a 10km flat TT".
I just copied Specialized marketing chart and gave it real numbers.

Although I’m a Midwestern crit racer and have literally seen races where my elevation gain was 16ft, they also have 200+ accelerations from 24mph to 30mph. Gotta believe that weight means something when trying to accelerate. How much? I have no idea.

I’ve also thought maybe the slope of the utility function is more curved than straight, but curves are harder to draw so I went with straight Image
2018 Canyon Aeroad Disc - 7.1kg | 2018 Specialized Crux - 8.0kg

Retired: 2015 Giant Propel Advanced SL - 7.0kg | 2018 Santa Cruz Stigmata - 6.8kg | 2018 Trek Madone 9.0 - 7.1kg | Switch Single Speed - 5.9kg

User avatar
iflyadesk
Posts: 136
Joined: Thu Oct 11, 2012 2:18 am
Location: Chicago, IL

by iflyadesk

pmprego wrote:I continue to find the aeroad tour results weird. It means that any manufacturer wasn't able to beat a bike that is now several years old.

Canyon has some type of holy grail of intelligence. Sorry but that is not likely. Actually, it's probably not true as canyon is not likely to have more R&D than firms like specialized or cannondale or giant that have way bigger budgets.
My theory is that Specialized and Trek have a more advanced testing protocol that takes into consideration more yaw angles, more real life trade offs like buffeting wind, etc, and the simple test Tour does matches the old (at this point) idea to just test 0° steady state airflow.

I could be completely wrong. Would love to find out that both Canyon and Tour mag are more sophisticated than that!


Sent from my iPhone using Tapatalk
2018 Canyon Aeroad Disc - 7.1kg | 2018 Specialized Crux - 8.0kg

Retired: 2015 Giant Propel Advanced SL - 7.0kg | 2018 Santa Cruz Stigmata - 6.8kg | 2018 Trek Madone 9.0 - 7.1kg | Switch Single Speed - 5.9kg

by Weenie


Steve Curtis
Posts: 346
Joined: Thu Jul 31, 2008 12:20 pm
Location: Hampshire UK, Dublin Ireland and Geneva Switzerland.

by Steve Curtis

.[/quote]
My theory is that Specialized and Trek have a more advanced testing protocol that takes into consideration more yaw angles, more real life trade offs like buffeting wind, etc,

[/quote]

Or they make it up to suit their agenda knowing it can't be disproved. Or skew the numbers based on unknown permutations.
Anyhow, it would appear people lap this up.

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