Aero bikes, are they really 'aero'?
carbineacs
Posts: 65
I've been following and looking at some aero bikes recently, and something is bugging me.
Are they really aero? I'm not going to profess to being an aerodynamics expert, but I do have a basic understanding.
I'm going to target two desirable aero bikes as examples. The Trek Madone, and the Scott Foil.
Both of these bikes have large, flat sections on them facing the rear of the bike. On the Madone, it's the down tube where the bottle mounts and Di2 junction goes. The whole downtube at the 'rear' is flat. The proprietary brakes are also surprisingly flat faced. On the Scott Foil, it's the seattube. The entire rear face of it is flat. I've seen a few other aero bikes like that too.
I may be over simplifying things here, but a large flat surface, is going to cause low pressure directly behind it, causing air to be pushed into the space it occupies, therefore causing drag and you the rider, having to use more energy to push the bike through that moving forward.
To make it even simpler (to me), I can't recall seeing anything that's designed to cut through the air for maximum efficiency, have any flat sections on it. Aircraft being a very good example. Every trailing edge is as thin as possible to reduce drag, and keep lift. Race cars don't count as they are trying to create drag in places to cause downforce.
I know bike manufacturers are marketing experts, and of course I've read that the rider position has a far greater impact on drag than the bike itself. Every bike mag, website, article on this seems to point to 'science' saying that weight mean nothing and aero is everything. So I'm thinking, have we all been really duped by excellent marketing, and I wonder how long the next big thing will be.. I suspect it will be 'weight is everything, aero doesn't mean anything under 40mph'!
So, can any aero or physics experts put me right? I can't find anything (I trust) on the Madone's aero credentials really. However, regardless of how aero it really is, it's a bloody nice looking bike!
Are they really aero? I'm not going to profess to being an aerodynamics expert, but I do have a basic understanding.
I'm going to target two desirable aero bikes as examples. The Trek Madone, and the Scott Foil.
Both of these bikes have large, flat sections on them facing the rear of the bike. On the Madone, it's the down tube where the bottle mounts and Di2 junction goes. The whole downtube at the 'rear' is flat. The proprietary brakes are also surprisingly flat faced. On the Scott Foil, it's the seattube. The entire rear face of it is flat. I've seen a few other aero bikes like that too.
I may be over simplifying things here, but a large flat surface, is going to cause low pressure directly behind it, causing air to be pushed into the space it occupies, therefore causing drag and you the rider, having to use more energy to push the bike through that moving forward.
To make it even simpler (to me), I can't recall seeing anything that's designed to cut through the air for maximum efficiency, have any flat sections on it. Aircraft being a very good example. Every trailing edge is as thin as possible to reduce drag, and keep lift. Race cars don't count as they are trying to create drag in places to cause downforce.
I know bike manufacturers are marketing experts, and of course I've read that the rider position has a far greater impact on drag than the bike itself. Every bike mag, website, article on this seems to point to 'science' saying that weight mean nothing and aero is everything. So I'm thinking, have we all been really duped by excellent marketing, and I wonder how long the next big thing will be.. I suspect it will be 'weight is everything, aero doesn't mean anything under 40mph'!
So, can any aero or physics experts put me right? I can't find anything (I trust) on the Madone's aero credentials really. However, regardless of how aero it really is, it's a bloody nice looking bike!
Rule #65 // Maintain and respect your machine.
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The seatpost is never going to be an area where you get much clean air in the first place. Considering you and your legs are above and either side of it. The from end of the bike around the headtube and around the fork are most beneficial of aero design as they are the bits pushing through the air. Lots of aero seatpost are prone to slipping so it’s best to have reliability over a bit of aero shaping which in reality is going to be quite minimal0
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thegreatdivide wrote:
Short answer to my long question! A quick search with 'Madone Kamm principle' and I get;
https://www.trekbikes.com/us/en_US/insi ... tual_foil/
Which explains it all.. I've not seen that before on the site and I spend too much time looking at Madones!
I will stay a bit cynical about it as some more physics based resources say the Kamm principle must be executed perfectly (which a lot of car manufactures haven't done right..) but I will tentatively trust Trek's engineers!
Thanks for the info, now I know the right terminology I can look into it a bit more.Rule #65 // Maintain and respect your machine.0 -
I don't notice a difference between my Moda Stretto and my bottom level Specialised Secteur tbh0
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Get a head on shot of anyone on a bike and you'll see that the rider is by far the biggest area and drag.
I'm sure aero bikes are more aero than ones that aren't - but I can't see it's noticeable.
I have an aero bike but mainly cos I like the look of it. No kamm tails though...0 -
Kamm principle, the UCI's 3-1 rule (although now outdated, these bikes were designed with that rule in mind), weight considerations?
I have a Foil, I can't notice any difference between it and my last non-aero bike. Looks nice to me though!0 -
Poptart242 wrote:Kamm principle, the UCI's 3-1 rule (although now outdated, these bikes were designed with that rule in mind), weight considerations?
I have a Foil, I can't notice any difference between it and my last non-aero bike. Looks nice to me though!
That's my main thing about them, they do look good! Scott Foil is a good looking bike for sure. Bianchi Oltre XR4 is my favourite but I would have to have it in red and I think that would upset people..
I was speaking to some extremely talented cyclists the other week, one a cycling sports scientist who trains a national team, and the other who cycles fast for a living, has many years under him and is also very talented. One was adamant weight was far more critical than aero (rider + bike) as you're always climbing something, nothing is really 'flat', and the other was saying aero is critical, weight is not!
It would be interesting to see what other people say about going from an aero to 'normal' race bike.. I wonder if Sagan would really notice a difference, or even lose, between his Venge and Tarmac in a sprint.. I suspect not!
Unfortunately neither of my bikes are aero or amazingly light (like, Emonda SLR9 light) so I can't tell, but I'm sure my 500g lighter bike with carbon wheels 'feels' faster.. wish I knew for sure if it is or not..Rule #65 // Maintain and respect your machine.0 -
the aero bike will be more aero, than an standard bike, but really as others have said, its the thing on top and the position they are in that's the biggest contributing factor.
going back to my recent bikes, the aero one was faster on the flat, than the non aero one... but elsewhere it wasn't quite as good....0
