Minimising cross-wind buffeting: Aero, round-tube, or?

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Prawn
Posts: 126
Joined: Tue Mar 20, 2018 5:44 am

by Prawn

If I was a really good rider, I'm sure this wouldn't be an issue: I don't like the feeling of being throw around by cross-winds, especially when the wind is gusty.

This got me wondering: What type of frame is the least susceptible to wind gusts? ...and what is the relative contribution of frames and wheels in this regard?

Some initial observations:
  • There is nothing more aero than air. ...so maybe the answer is something like 'the shape doesn't matter much - just minimise the cross-sectional area presented to the cross-wind'
    An aero section may not be so 'aero' when a gust hits from the side (and presumably detaches flow).
    A cylinder isn't a great shape in terms of drag - but it beats a box section (which may be how an aero shape appears to a side gust).
    There may be some compromises between drag when there are low yaw angles of wind and susceptability to cross-winds; the objective is to minimise cross-wind susceptability regardless of overall 'aeroness'
What do you think? What does your experience suggest?

by Weenie


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RNAV
Posts: 81
Joined: Sat Apr 18, 2020 3:55 pm

by RNAV

I'd be willing to bet that any differences between frame tube shapes will be imperceptible to the rider under crosswind conditions. Any differences in wheel depth, however, will be perceptible.

I've ridden both round tube bikes and aero bikes, both with shallow wheels. I've ridden both round tube bikes and aero bikes, both with deep section wheels. Speaking specifically to crosswind handling, the only thing that made a noticeable difference was the depth of the wheels.

Butcher
Shop Owner
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by Butcher

I'll second that thought.

Marin
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Location: Vienna Austria

by Marin

Frame ist mostly irrelevant. Front wheel matters.

Lakal
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Joined: Thu Apr 23, 2020 12:20 pm

by Lakal

I went from a 35mm*26mm(width) to a 45mm*28mm front wheel. Both Farsports.
The 45mm*28mm front wheel is much more stable in crosswinds so i guess the width of the front wheel is important too.

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cyclespeed
Posts: 905
Joined: Mon Jun 06, 2016 8:45 am

by cyclespeed

My SL6 Sworks on 50mm deep wheels was far less susceptible to crosswinds than my Factor OStro on the same depth wheels, so for me at least, yes, the frame design does matter.

You can see immediately that the Ostro has a lot more real estate side on than the SL6. And it's mostly designed to be cutting through the air going forwards, not sideways, so Cd will be very poor side on.

RNAV
Posts: 81
Joined: Sat Apr 18, 2020 3:55 pm

by RNAV

cyclespeed wrote:
Mon Sep 20, 2021 2:01 pm
My SL6 Sworks on 50mm deep wheels was far less susceptible to crosswinds than my Factor OStro on the same depth wheels, so for me at least, yes, the frame design does matter.

You can see immediately that the Ostro has a lot more real estate side on than the SL6. And it's mostly designed to be cutting through the air going forwards, not sideways, so Cd will be very poor side on.
Just curious, were they the exact same wheelset? Some wheel manufacturers market that their wheel profiles are designed for improved stability/aerodynamic benefits in crosswinds. I understand the wheel depths were the same, but if they weren't the exact same wheel set, you're dealing with two variables (different wheels, different frame) vs one variable (same wheels, different frame).

I get what you're saying, though: an aero tri bike frame will likely catch more crosswind then a round tube frame.

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wheelsONfire
Posts: 4528
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

Prawn wrote:
Sun Sep 19, 2021 7:41 am
If I was a really good rider, I'm sure this wouldn't be an issue: I don't like the feeling of being throw around by cross-winds, especially when the wind is gusty.

This got me wondering: What type of frame is the least susceptible to wind gusts? ...and what is the relative contribution of frames and wheels in this regard?

Some initial observations:
  • There is nothing more aero than air. ...so maybe the answer is something like 'the shape doesn't matter much - just minimise the cross-sectional area presented to the cross-wind'
    An aero section may not be so 'aero' when a gust hits from the side (and presumably detaches flow).
    A cylinder isn't a great shape in terms of drag - but it beats a box section (which may be how an aero shape appears to a side gust).
    There may be some compromises between drag when there are low yaw angles of wind and susceptability to cross-winds; the objective is to minimise cross-wind susceptability regardless of overall 'aeroness'
What do you think? What does your experience suggest?
I do think the frame will have an effect. How much we perceive it's an issue or not is subjective. Just as a deeper front wheel is a problem or not a big deal.
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

Hexsense
Posts: 2257
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

So, slim round tube is not aero.
Massively deep aero tube is not stable in crosswind.
Then simply slim aero tube like the current SuperSix? It's slimmer than Tarmac SL7 and most other similar bikes.

I feel the difference in lean angle against stiff constant cross wind between my SuperSix and my Allez Sprint. Allez Sprint need more lean angle to fight the wind. SuperSix barely need any lean into the wind. Biggest difference between SuperSix's shape versus Allez Sprint are the seat post and seat tube depth and truncated down tube on SuperSix VS oval-ish on Allez Sprint.

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

by TobinHatesYou

My Madone has been blown over a couple times when leaned against fences. My Emonda and CR1 never did. It definitely makes a difference in high yaw crosswinds. At lower yaw an aero bike is probably more stable than a non-aero bike.

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cyclespeed
Posts: 905
Joined: Mon Jun 06, 2016 8:45 am

by cyclespeed

RNAV wrote:
Mon Sep 20, 2021 6:47 pm
cyclespeed wrote:
Mon Sep 20, 2021 2:01 pm
My SL6 Sworks on 50mm deep wheels was far less susceptible to crosswinds than my Factor OStro on the same depth wheels, so for me at least, yes, the frame design does matter.

You can see immediately that the Ostro has a lot more real estate side on than the SL6. And it's mostly designed to be cutting through the air going forwards, not sideways, so Cd will be very poor side on.
Just curious, were they the exact same wheelset? Some wheel manufacturers market that their wheel profiles are designed for improved stability/aerodynamic benefits in crosswinds. I understand the wheel depths were the same, but if they weren't the exact same wheel set, you're dealing with two variables (different wheels, different frame) vs one variable (same wheels, different frame).

I get what you're saying, though: an aero tri bike frame will likely catch more crosswind then a round tube frame.
Good point - Sworks had Campa Bora Ultra 50, the Ostro DeCadence 50. But the profiles and widths are extremely similar, and I cannot believe that the difference comes from the wheels.

This thread kind of confirms my suspicions that if it's a breezy, blustery day, you may be better off on a non aero bike, or at least one that doesn't have super deep profiles. I find they work best on still days, with as little yaw as possible.

Nickldn
Posts: 919
Joined: Mon Mar 25, 2019 12:35 am

by Nickldn

cyclespeed wrote:
Tue Sep 21, 2021 9:25 am
RNAV wrote:
Mon Sep 20, 2021 6:47 pm
cyclespeed wrote:
Mon Sep 20, 2021 2:01 pm
My SL6 Sworks on 50mm deep wheels was far less susceptible to crosswinds than my Factor OStro on the same depth wheels, so for me at least, yes, the frame design does matter.

You can see immediately that the Ostro has a lot more real estate side on than the SL6. And it's mostly designed to be cutting through the air going forwards, not sideways, so Cd will be very poor side on.
Just curious, were they the exact same wheelset? Some wheel manufacturers market that their wheel profiles are designed for improved stability/aerodynamic benefits in crosswinds. I understand the wheel depths were the same, but if they weren't the exact same wheel set, you're dealing with two variables (different wheels, different frame) vs one variable (same wheels, different frame).

I get what you're saying, though: an aero tri bike frame will likely catch more crosswind then a round tube frame.
Good point - Sworks had Campa Bora Ultra 50, the Ostro DeCadence 50. But the profiles and widths are extremely similar, and I cannot believe that the difference comes from the wheels.

This thread kind of confirms my suspicions that if it's a breezy, blustery day, you may be better off on a non aero bike, or at least one that doesn't have super deep profiles. I find they work best on still days, with as little yaw as possible.
I have 2 bikes:

* one with 55mm deep wheels and plenty of untruncated aerofoils on the frame,

* the other with slightly shallower 45mm wheels and truncated aerofoils making up the frame.

I feel crosswinds much more on the first bike, the second one is relatively immune to crosswinds. I don't think it's the wheels that make such a huge difference, I think it's the frame has a lot to do with it too.

Wheels may have been a culprit in the past, but now most are pretty stable. So yeah the frame has to be a factor.
Giant Propel Advanced SL Red Etap 11s Easton EC90 wheels CeramicSpeed BB 6.5kg

Vitus ZX1 CRS Campy Chorus 12s Bora WTO 45 disk brake wheels Yoeleo H10 bars 7.5kg

Andrew69
Posts: 445
Joined: Thu Feb 19, 2009 10:52 am
Location: ɹǝpunuʍop

by Andrew69

Nickldn wrote:
Tue Sep 21, 2021 9:35 am
I feel crosswinds much more on the first bike, the second one is relatively immune to crosswinds. I don't think it's the wheels that make such a huge difference, I think it's the frame has a lot to do with it too.

Wheels may have been a culprit in the past, but now most are pretty stable. So yeah the frame has to be a factor.
I think it depends on exactly what kind of winds we're talking about
A steady cross wind and most new generation wheels are pretty good, but in very gusty wind, depth of front wheel will still be more important than frame tube shape simply due to the mechanics of steering and the fact the fork is in effect a lever for forces acting on the front wheel.

The closest Ive ever come to crashing in a crosswind was recently when my handlebars were almost reefed out of my hands as I had a very gusty wind hit the front wheel right as I went between 2 buildings which acted as a wind tunnel and funnel the wind through with even more force.
Yet same road with a steady wind, no problem

by Weenie


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