Aero Frame Flex

Discuss light weight issues concerning road bikes & parts.
Post Reply
Wildh
Posts: 36
Joined: Fri Apr 01, 2016 6:11 pm

by Wildh

I'm just doing some general research and can't seem to find a lot of info out there showing any pictures or videos of frame flex with aero frames. Since I live in an area where bikes are not plentiful, I'm curious about other frames.

This video is a Workswell 081. I'm holding the seat steady and applying a moderate side to side force at the steerer to replicate a sort of torsional force that maybe similar during a very hard in the saddle effort.



What do those of you with say a Canyon Aeroad see? I ask because that is a similar design in frames.

Again, this is more experimental and I'm not trying to get into a bashing competition for open mold frames vs major brands. If this is strictly a result of an interior frame, that is fine. We can discuss that, but let's stay civil.

I did not repeat this exercise with other frames via video, but I had a chance to do this with a Madone and a Bianchi XR4. I was surprised. The Madone was quite rigid which is what expected. The Bianchi felt closer to the 081. That is essentially what got me to thinking and wondering if others have done similar exercises.

by Weenie


jfranci3
Posts: 271
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

That's a lot of flex, but the trainer can put a lot stress on the bike you'd flat out never see on the road.
You've got a lot more leverage standing 2ft away from the bike which is solidly mounted in the trainer, which also has a lot of leverage. You're also measuring steering column to rear stay rigidity rather than steering column to crank. Also, it's very uncommon to apply force in that direction when riding the bike, as you'd fall over. You also cannot apply that force force that direction to the head tube as you'd normally have he cranks adsorbing your base leverage and the bars deflecting or turning, adsorbing your upper body forces. You're also seeing a lot of front wheel roll magnified by the height.

This suggests that if you lock down the fork and the rear, put 45kg on the crank, you should see about .75mm of deflection. You can also lock the crank down and put a known load on the head tube. You should see about 99nm/deg.
Last edited by jfranci3 on Tue Apr 17, 2018 2:57 am, edited 3 times in total.

Wildh
Posts: 36
Joined: Fri Apr 01, 2016 6:11 pm

by Wildh

Thanks for the response. Yes I thought about that in regards to the trainer. It's not much difference off the bike but for purposes of video stability, I thought it would be better clamped in and viewing it with one static point.

I agree it's not a force that is common in normal riding and to be fair, in a stand up Sprint, the seat tube will sway and not be static as is in my application here. Also, bottom bracket stiffness in this bike is about as good as any I've ridden so power transfer is not sacrificed. The only time I notice it is on the trainer or when I'm in a seated position and apply a pressure on one side of the handlebar or the other. It's much more subtle when of the trainer and under normal riding.

Again, this is more of a post to discuss the pros and cons of various points of frame flex and the trade off on performance so it's not too make over generalized opinions or biases and your response was excellent in that regards.

I can see some advantage of top tube having some give for ride compliance but more in the vertical axis.

adam0bmx0
Posts: 6
Joined: Tue Mar 13, 2018 5:10 am
Location: Brisbane, AU

by adam0bmx0

I've got 2 aero bikes and 2 non-aero bikes I've done my 'wiggle' test on. :D

That is whilst riding, sat in the saddle, hands on the hoods, try and deflect the bike side to side with your arms keeping you butt firmly planted.

Granted a few things come into play, but it's noticable between frames.

2014 Cervelo S5, wiggles alot! 2016 Focus Izalco Max, wiggles a moderate amount, not as much as the S5, 2016 BMC Team machine and 2016 Time machine (SLR02 and TMR02 models) very little wiggle movement, and generally feel much stiffer overall.

Wildh
Posts: 36
Joined: Fri Apr 01, 2016 6:11 pm

by Wildh

The wiggle test! Yes that is a good explanation. And your right... It's very different from bike to bike. I have a gt grade which uses a triple triangle design and there is NO flex when performing the wiggle test. That bike is very comfortable riding with very thinned out stays. It's a really a wonderful all around bike. Not very fast though. It's very upright.

User avatar
Juanmoretime
Administrator
Posts: 7089
Joined: Sat Jun 19, 2004 11:08 am
Location: Urbana, Illinois

by Juanmoretime

I went from a Lynsey R320 which cornered awesome to a Blue AC1 and while the Blue is a much more comfortable ride when it comes to stiffness I can tell the difference when cornering. The Blue is very inspiring when cornering hard.
RESIDENT GRUMPY OLD MAN.

Toby
Posts: 48
Joined: Thu Sep 06, 2012 4:30 am

by Toby

Juanmoretime wrote:
Tue Apr 17, 2018 10:18 am
I went from a Lynsey R320 which cornered awesome to a Blue AC1 and while the Blue is a much more comfortable ride when it comes to stiffness I can tell the difference when cornering. The Blue is very inspiring when cornering hard.
Did you mean that the Lynskey is much more comfortable, or that the Blue is both more comfortable and more confident in corners?

User avatar
Juanmoretime
Administrator
Posts: 7089
Joined: Sat Jun 19, 2004 11:08 am
Location: Urbana, Illinois

by Juanmoretime

Typo and not enough coffee. The Blue is definitely more comfortable.
RESIDENT GRUMPY OLD MAN.

peted76
Posts: 243
Joined: Mon Jun 23, 2014 10:30 pm

by peted76

Subscribed.

User avatar
Calnago
Posts: 6381
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

I love the “Wiggle Test”. I think it gives a pretty good indication of front end handling characteristics. I can do it in a block of riding. Just sort of try to flick the front end as if you’re trying to initiate a speed wobble or other bad things. Obviously don’t go crazy and don’t do it at speed down a hill. But if it seems a little too easy to get a lot of “wiggle”, then you can expect the same characteristic to be present when you run into a bit of trouble at speed or descending. The hard part is determining what is the right tradeoff for you in particular in terms of how stiff or wiggly you like it.
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

by Weenie


Post Reply
  • Similar Topics
    Replies
    Views
    Last post