2021 Road Bike Stiffness Chart

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C36
Posts: 2554
Joined: Fri Mar 03, 2017 3:24 am

by C36

Deformation is linear for structures like frames in the elastic domain (wheels may be different when spokes loose too many tension for example). Twice the force would give you twice the deformation.

Those tests are quite standards to engineer a frame. questioning their relevance is like questioning any calculation Engineers would do, they are an important part of performance (I know at least one pro team that individually test their pro frames before accepting them, and do reject some).
Their Interpretation though is a different story but as a general rule (from my experience and an old discussion with Cannondale and Canyon engineers), front end / fork stiffness would be noticeable out of the saddle acceleration (the “crisp”). I hold a similar table than OP where I put in perspective the bikes tried (must have tried around 20 of the frames that passed by Tour over last years) and the lab results, that helps in analysing those values.


—————————————
- Supersix evo2 HM 5707g
- 1995 Miguel Indurain Pinarello restauration project
- R3000si Junior bike restauration project.

by Weenie


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MikeD
Posts: 1042
Joined: Thu Dec 11, 2014 9:55 pm

by MikeD

spartacus wrote:
MikeD wrote:
Sat Mar 13, 2021 8:08 pm
In general, I prefer a stiff frame and fork to a flexy one, and get my comfort from wider, lower pressure tires, padded bar tape and gloves, and a comfortable saddle. In my opinion, flexy frames are more prone to shimmy, handle poorly, and waste energy by flexing instead of putting that pedaling force to the rear wheel.
The problem with this chart though is it might lead someone to believe a bike is "flexy" like the SL7 for example which certainly does not feel very flexy.
Also, I would think a heavier rider would consider a particular frame flexy whereas a light weight rider wouldn't.

spartacus
Posts: 1049
Joined: Mon Apr 04, 2011 6:53 pm

by spartacus

MikeD wrote:
Sat Mar 13, 2021 10:25 pm
spartacus wrote:
MikeD wrote:
Sat Mar 13, 2021 8:08 pm
In general, I prefer a stiff frame and fork to a flexy one, and get my comfort from wider, lower pressure tires, padded bar tape and gloves, and a comfortable saddle. In my opinion, flexy frames are more prone to shimmy, handle poorly, and waste energy by flexing instead of putting that pedaling force to the rear wheel.
The problem with this chart though is it might lead someone to believe a bike is "flexy" like the SL7 for example which certainly does not feel very flexy.
Also, I would think a heavier rider would consider a particular frame flexy whereas a light weight rider wouldn't.
That's definitely true and some manufacturers tune the stiffness of different frame sizes so it makes me wonder if that is a factor in this test.

As for "deformation is linear in the elastic domain" - This is flex at a junction between four tubes and who knows how many pieces of carbon weave so maybe not the entire structure reaches the point where it can no longer flex at the same time? Certainly not every frame even with the same N/mm can flex the same maximum amount?

stevesbike
Posts: 333
Joined: Thu Oct 24, 2019 5:33 pm

by stevesbike

spartacus wrote:
Sat Mar 13, 2021 10:36 pm
MikeD wrote:
Sat Mar 13, 2021 10:25 pm
spartacus wrote:
MikeD wrote:
Sat Mar 13, 2021 8:08 pm
In general, I prefer a stiff frame and fork to a flexy one, and get my comfort from wider, lower pressure tires, padded bar tape and gloves, and a comfortable saddle. In my opinion, flexy frames are more prone to shimmy, handle poorly, and waste energy by flexing instead of putting that pedaling force to the rear wheel.
The problem with this chart though is it might lead someone to believe a bike is "flexy" like the SL7 for example which certainly does not feel very flexy.
Also, I would think a heavier rider would consider a particular frame flexy whereas a light weight rider wouldn't.
That's definitely true and some manufacturers tune the stiffness of different frame sizes so it makes me wonder if that is a factor in this test.

As for "deformation is linear in the elastic domain" - This is flex at a junction between four tubes and who knows how many pieces of carbon weave so maybe not the entire structure reaches the point where it can no longer flex at the same time? Certainly not every frame even with the same N/mm can flex the same maximum amount?
some of your prior remarks conflate transversal stiffness (what Tour tested) and eccentric stiffness (affected by pedaling action) and the former is meant more as a benchmark than a replication of both the torque and force applied by a rider. As a benchmark, the issue of linearity of transversal stiffness doesn't much matter.

dbzznlqbqft
Posts: 57
Joined: Sun Jul 05, 2020 11:02 pm

by dbzznlqbqft

wheelsONfire wrote:
Sat Mar 13, 2021 8:10 pm
Check data of the new Ax Vial EVO instead. I think it'll come out as one of the stiffest
Interesting, I never thought AX updated a new vial. What makes you think it is one of the stiffest? Would you like to share some data?

dbzznlqbqft
Posts: 57
Joined: Sun Jul 05, 2020 11:02 pm

by dbzznlqbqft

spartan wrote:
Sat Mar 13, 2021 2:48 pm
so the peak TARMAC was the SL6 lighter / stiffer/ more compliant than the SL7. yes SL7 is at best 3-5 watts faster but marginal.
It seems sometimes designing an aero shape will compromise some stiffness and weight.
As an unprofessional, I do consider rim-brake SW SL6 much better than SW SL7 simply lighter, stiffer, and some adequate-already aero design.

RDY
Posts: 2587
Joined: Thu Jul 30, 2020 10:31 pm

by RDY

I've heard a lot of Trek riders complaining about disc rub when out of the saddle. If this testing is anything to go by, they seem to have very whippy forks and headtubes almost across the board, relative to some of the other manufacturers (and noodle BBs).

Difficult to see how they manage it given how heavy they are relative to the rest of the industry.

On the other end of the spectrum, Giant's waifish TCRs are very light and yet very stiff.

TobinHatesYou
Posts: 13050
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RDY wrote:
Sun Mar 14, 2021 4:09 am
I've heard a lot of Trek riders complaining about disc rub when out of the saddle. If this testing is anything to go by, they seem to have very whippy forks and headtubes almost across the board, relative to some of the other manufacturers (and noodle BBs).

Difficult to see how they manage it given how heavy they are relative to the rest of the industry.

On the other end of the spectrum, Giant's waifish TCRs are very light and yet very stiff.

Not sure HT stiffness matters for brake rub, but it might matter for stuff like speed wobbles.

My 2018 Emonda SLR Disc's brakes don't rub when out of the saddle, but the Madone SLR Disc is more susceptible. It's likely that very localized flex at the flat mounts is the main contributor...not sure what Tour Mag's methodology is here because they measured greater stiffness in the Madone fork than the Emonda.

jfranci3
Posts: 1605
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

C36 wrote:
Sat Mar 13, 2021 9:56 pm
Deformation is linear for structures like frames in the elastic domain (wheels may be different when spokes loose too many tension for example). Twice the force would give you twice the deformation.

Those tests are quite standards to engineer a frame. questioning their relevance is like questioning any calculation Engineers would do, they are an important part of performance (I know at least one pro team that individually test their pro frames before accepting them, and do reject some).
Their Interpretation though is a different story but as a general rule (from my experience and an old discussion with Cannondale and Canyon engineers), front end / fork stiffness would be noticeable out of the saddle acceleration (the “crisp”). I hold a similar table than OP where I put in perspective the bikes tried (must have tried around 20 of the frames that passed by Tour over last years) and the lab results, that helps in analysing those values.


—————————————
- Supersix evo2 HM 5707g
- 1995 Miguel Indurain Pinarello restauration project
- R3000si Junior bike restauration project.
This is not a simple structure which is why you need to preload it and the on-center to preload ramp will look different than the preload -after. Again, those stiffnesses aren't indexed to anything, nor rated for importance (for example, the BB is always going to try to move under you, limiting its values importance; while the fork best to be flexy so long as it doesn't run the rotors for mid-turn bumps and it doesn't contribute to perceived stiffness)

Additionally, load the frame is deforming as you apply load so the angle of attack and leverage will be reduced as you apply load (if you press down on the pedal and the BB deflects down and in, you're now pressing the pedal down closer to the frame (a reduced "q" factor)). The spring rate increases as everything deflects.

In any case, on these bikes in the core sizes, your handle bars and stem are going contribute a lot more to the perceived stiffness than the frame. If you want stiffer, get a smaller bar and stem. For cornering,it still vertical load (otherwise you'd fall when you hit the tiniest bump). The bike frame only feels real lateral flex when you're at full sprint, out of the saddle, yanking on the bars - even then, you're moving the bike around under you, reducing the lateral loads. The bike is alway going to try to make any lateral load vertical.

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wheelsONfire
Posts: 6394
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Location: NorthEU

by wheelsONfire

dbzznlqbqft wrote:
Sun Mar 14, 2021 12:35 am
wheelsONfire wrote:
Sat Mar 13, 2021 8:10 pm
Check data of the new Ax Vial EVO instead. I think it'll come out as one of the stiffest
Interesting, I never thought AX updated a new vial. What makes you think it is one of the stiffest? Would you like to share some data?
https://bikerumor-wpengine.netdna-ssl.c ... n-test.jpg

https://bikerumor.com/2020/08/18/ax-lig ... Ima_zyTnxo

I have the last version with rim brakes and i have had the first Vial EVO D and a later version. Now as mentioned, Vial EVO Race rim brake.
The Disc version is based on the rim version, but revised accordingly for disc brakes.
Bikes:

Ax Lightness Vial EVO Race (2019.01.03)
Open *UP* (2016.04.14)
Paduano Racing Fidia (kind of shelved)


Ex bike; Vial EVO D, Vial EVO Ultra, Scott Foil, Paduano ti bike.

User avatar
C36
Posts: 2554
Joined: Fri Mar 03, 2017 3:24 am

by C36

jfranci3 wrote:
This is not a simple structure which is why you need to preload it and the on-center to preload ramp will look different than the preload -after. Again, those stiffnesses aren't indexed to anything, nor rated for importance (for example, the BB is always going to try to move under you, limiting its values importance; while the fork best to be flexy so long as it doesn't run the rotors for mid-turn bumps and it doesn't contribute to perceived stiffness)

Additionally, load the frame is deforming as you apply load so the angle of attack and leverage will be reduced as you apply load (if you press down on the pedal and the BB deflects down and in, you're now pressing the pedal down closer to the frame (a reduced "q" factor)). The spring rate increases as everything deflects.

In any case, on these bikes in the core sizes, your handle bars and stem are going contribute a lot more to the perceived stiffness than the frame. If you want stiffer, get a smaller bar and stem. For cornering,it still vertical load (otherwise you'd fall when you hit the tiniest bump). The bike frame only feels real lateral flex when you're at full sprint, out of the saddle, yanking on the bars - even then, you're moving the bike around under you, reducing the lateral loads. The bike is alway going to try to make any lateral load vertical.
Not sure I totally follow but frames do behave linearly since the start of the load. No magics, it follows physics.
Regarding the changes in load and « lever » during the put of the saddle pedal stroke (if I understand you), that’s an important point, the bike is more inclined during the 2-5 o’clock phase of the downstroke, when you generate more force, then the need to measure this aspect.

Finally regarding bar and stem stiffness, from blind tests, it’s the least perceived change. People are quite incapable of determining how it impacts their bike stiffness. Partially linked to the little force your arm have compared to your legs and the relatively short lever compared to a fork or a wheel


—————————————
- Supersix evo2 HM 5707g
- 1995 Miguel Indurain Pinarello restauration project
- R3000si Junior bike restauration project.

dbzznlqbqft
Posts: 57
Joined: Sun Jul 05, 2020 11:02 pm

by dbzznlqbqft

wheelsONfire wrote:
Sun Mar 14, 2021 2:11 pm
dbzznlqbqft wrote:
Sun Mar 14, 2021 12:35 am
wheelsONfire wrote:
Sat Mar 13, 2021 8:10 pm
Check data of the new Ax Vial EVO instead. I think it'll come out as one of the stiffest
Interesting, I never thought AX updated a new vial. What makes you think it is one of the stiffest? Would you like to share some data?
https://bikerumor-wpengine.netdna-ssl.c ... n-test.jpg

https://bikerumor.com/2020/08/18/ax-lig ... Ima_zyTnxo

I have the last version with rim brakes and i have had the first Vial EVO D and a later version. Now as mentioned, Vial EVO Race rim brake.
The Disc version is based on the rim version, but revised accordingly for disc brakes.
Look what I just found, some tour data for German superlight weight bikes. https://www.benobikes.com/en/news/revie ... ers-tested

You're right about Vial evo, it seems that it's comparable to RCA and maybe even better.

rudye9mr
Posts: 578
Joined: Wed May 01, 2019 12:01 pm

by rudye9mr

rudye9mr wrote:
Fri Aug 07, 2020 11:10 am
Dr.Dos wrote:
Thu Aug 06, 2020 6:59 pm
Image
^219w @45kmph / Tour Magazine - fyi

Luftwiderstand (Drag), 45km/h... 219W
Gewicht Komplettrad (Weight / complete Bike)....7.9Kg
Lenkkopfsteifigkeit (Steering Head Rigidity /Stem?)).....99Nm/deg
Seitensteifigkeit Gabel (Lateral Rigidity Fork)....57N/mm
Tretlagersteifigkeit (Bottom Bracket Stiffness)......69N/mm
Federharte Sattelstutze (Spring hard seat post)...297N/mm

Gewicht Rahmen (Frame Weight)...1.340 Kg
Gabel (Fork).......0.425 Kg
Steuerlager........0.096 Kg
can you add to spreadsheet please? ^source and data above...tx

dbzznlqbqft
Posts: 57
Joined: Sun Jul 05, 2020 11:02 pm

by dbzznlqbqft

rudye9mr wrote:
Mon Mar 15, 2021 12:51 am
rudye9mr wrote:
Fri Aug 07, 2020 11:10 am
Dr.Dos wrote:
Thu Aug 06, 2020 6:59 pm
Image
^219w @45kmph / Tour Magazine - fyi

Luftwiderstand (Drag), 45km/h... 219W
Gewicht Komplettrad (Weight / complete Bike)....7.9Kg
Lenkkopfsteifigkeit (Steering Head Rigidity /Stem?)).....99Nm/deg
Seitensteifigkeit Gabel (Lateral Rigidity Fork)....57N/mm
Tretlagersteifigkeit (Bottom Bracket Stiffness)......69N/mm
Federharte Sattelstutze (Spring hard seat post)...297N/mm

Gewicht Rahmen (Frame Weight)...1.340 Kg
Gabel (Fork).......0.425 Kg
Steuerlager........0.096 Kg
can you add to spreadsheet please? ^source and data above...tx
Sure thing! Thanks :D

User avatar
wheelsONfire
Posts: 6394
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

dbzznlqbqft wrote:
Sun Mar 14, 2021 11:46 pm
wheelsONfire wrote:
Sun Mar 14, 2021 2:11 pm
dbzznlqbqft wrote:
Sun Mar 14, 2021 12:35 am
wheelsONfire wrote:
Sat Mar 13, 2021 8:10 pm
Check data of the new Ax Vial EVO instead. I think it'll come out as one of the stiffest
Interesting, I never thought AX updated a new vial. What makes you think it is one of the stiffest? Would you like to share some data?
https://bikerumor-wpengine.netdna-ssl.c ... n-test.jpg

https://bikerumor.com/2020/08/18/ax-lig ... Ima_zyTnxo

I have the last version with rim brakes and i have had the first Vial EVO D and a later version. Now as mentioned, Vial EVO Race rim brake.
The Disc version is based on the rim version, but revised accordingly for disc brakes.
Look what I just found, some tour data for German superlight weight bikes. https://www.benobikes.com/en/news/revie ... ers-tested

You're right about Vial evo, it seems that it's comparable to RCA and maybe even better.
It's better than RCA.
Bikes:

Ax Lightness Vial EVO Race (2019.01.03)
Open *UP* (2016.04.14)
Paduano Racing Fidia (kind of shelved)


Ex bike; Vial EVO D, Vial EVO Ultra, Scott Foil, Paduano ti bike.

by Weenie


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

www.starbike.com



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