I'm not talking specifically about triathlon frames, just frames which have aerodynamically shaped tubes. As I understand it, both types of frame are legal for road-racing under UCI rules.

So, why would one choose a traditional frame with round or "squoval" tubes over an aero frame? For example, why would one choose to ride a Cervélo R5 with (more) traditionally shaped tubes over a Cervélo S5 which would seem to be more aerodynamically sound?

Does it boil down to personal preference, or are there specific conditions in which one out-performs the other?

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    I strongly suspect that "streamlined" frames do not provide measurable improvement over standard round frames. They exist mostly for looks. And they likely weight a hair more and make it harder to add things like a strap-on water bottle holder. Oct 30, 2012 at 22:29
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    @DanielRHicks - the aero bikes do provide a very measurable difference over "standard" frames.
    – Ken Hiatt
    Oct 31, 2012 at 0:06
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    @DanielRHicks - You may have doubts but the differences have been measured in wind tunnels (with rotating front wheel) and also in field tests. Whether the difference is large enough to matter is a legitimate question; but whether the frames "provide measurable improvement" is not.
    – R. Chung
    Oct 31, 2012 at 0:46
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    @DanielRHicks - we can (and probably should) move this to a discussion room if you wish but these advantages don't disappear. Here's an example of a field test under real-world conditions that measured the difference between two frames that were already pretty aero. Subsequently the rider raced in a 40K TT and his actual time came within half a second per km of the predicted time.
    – R. Chung
    Oct 31, 2012 at 4:33
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    First, how could "a placebo effect" alter the recorded speed and power? Second, the field test was consistent with wind tunnel measurements. How could a placebo effect affect the wind tunnel? Third, I already pointed out that it was an example comparison of two frames that were already considered aero -- I used this example because the difference was smaller than usual. We really should move this to a discussion room if you wish to continue.
    – R. Chung
    Oct 31, 2012 at 17:08

2 Answers 2


Aero frames are generally slightly heavier than the standard frame you'd compare it to, though the difference might not even be enough for the average person to notice. Someone who regularly competes in time trials might want the increased speed on relatively flat ground, competitors will certainly notice the difference.

If you're not competing in time trials or triathlons and you don't have an extra couple thousand dollars burning a hole in your pocket, you would probably choose the standard, more compatible, traditional, and lighter frame that is going to perform perfectly well on your average terrain. If you frequently ride on hilly terrain, the added cost and weight of the aero frame isn't likely to be worth the trade off.


It will probably depend on terrain, speed, and other aerodynamic (or lack thereof) factors whether one would even notice a difference between an "aero" frame or a "normal" frame.

If you're climbing lots of hills, riding in traffic, or otherwise not in a position where wind resistance is your chief enemy, I doubt you'd see a benefit from going aero.

If you live out in the farmlands and ride on fast, flat roads, or somewhere that has lots of wind, you may notice a difference, because wind/air resistance becomes a factor.

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    Plus it seems to me like you should optimize the wind resistance of your body before your frame. Things like: wearing tight clothing, lowering your handlebars, using areobars, getting a more airo helmet seem like cheaper, easier alternatives that are not permanent investments. Nov 8, 2012 at 18:00

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