Yes that’s why I did 12 repetitions on each bike. So I actually rode 24km on each bike
So over 24 km there should have been 43 seconds cumulative time difference between the two bikes. In my tests the cumulative time difference was zero.
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You could also argue that 100km of riding outside is too open to differing conditions.
Ultimately all this back and forth supports my opinion than the difference is marginal.
I’d like to add I’m not an aero hater, I own an aero bike and I love riding it but I think we’ve been sold a bit of a lie.
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I think the benfits of aero frames are completely overblown - certainly way down the list of things that make the most improvement to aero as a whole and even further down the list of all the things that make you go quicker.
But…I absolutely love big fat aero frames and with silly aero features 
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Agreed it’s way down the list in terms of watts/$. If you’re happy with your non aero bike in every other way (stiffness, position, tyre clearance, brake type, etc) and are running aero wheels and fast tyres on it then can’t really justify the spend to replace it with an aero bike for that handful of watts. But if you’re buying a new bike anyway and it’s a choice between a brand’s aero vs traditional models which are pretty much the same price at any given spec point, and you care about speed, then it also seems a bit of a no brainer to go with the aero option. Unless there were other factors that were higher priority than speed e.g. Greater tyre clearance, or 2 piece bars for easier traveling.
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You posts sure seem to say otherwise
Maybe it’s not your intention, but it just comes off as an “old man yells at clouds” kind of post.
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I’ve done a few TTs on the same 10 mile course on two bikes
Bike 1 - Caad12, tririg front brake, cervelo s5 carbon aero handlebars, 50 carbon wheels, 25 mm gp5000, 54 tooth chainring, waxed chain.
Bike 2 - Orbea orca aero with downtube toolbox - 60 mm carbon wheels, 25 mm gp5000 front, 28 mm rear, alloy wiggle prime aero bars 2 cm narrower than caad12, 52 tooth chainring, front and rear lights fitted as rules demand lights now, waxed chain.
Same skinsuit, helmet, shoes etc.
Caad12
- 24.19 at 278 watts
- 24.57 at 268 watts
- 24.35 at 265 watts
Orbea orca aero
- 23.53 at 265 watts
- 23.40 at 273 watts
And just a fun data point on a faster course on the aero road bike
22.53 on 269 watts which is 26.5 mph or 42.6 kmh on a measly 270 watts 
This was full shrimp mode though.
My take home is I found at least 30 seconds (or 0.5 mph) over 10 miles going from an optimised non aero bike to an aero bike.
Aero bike also stops better, is more comfortable but is heavier.
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Nice data! I am going to do 150-300 watts in 50 watt increments, plus one all out TT effort on each bike on a 5 mile closed course, on a 2013 CAAD 10 and a 2023 System Six. I’m curious where the aero bike shines power & speed wise.
30" to 1’ over 10 miles doesn’t seem like a lot to a general cyclist, but that’s massive in a race, and can be the difference between getting caught and staying out of sight on a break away. That’s potentially 3 minutes in 30 miles… 
As I mentioned earlier in the thread for tt’s and even group racing any advantage no matter how little is always significant as 1 second can be the difference you’re looking for.
However for anyone else the savings are insignificant but buy the sexy bike that will get you out riding by all means.
It really didn’t to me.
⠀
David wrote:
and AJS914 wrote:
Be interested to know what speed that Tour test averaged…
But the above suggests, that for mere mortals (as David wrote) riding at 16-20mph - especially if riding with a group offering drafting oppos - then you’re probably in the realm of benefits that are barely, if at all, discernible. 
If it takes TT or race-like speeds and efforts for the (very real) benefit to become more clearly discernible, then David’s point seems pretty reasonable.
So now we’re at the point of refuting scientific data from multiple sources regarding aero bike savings because your gut feel and some guy’s “aero tests” on the internet say otherwise? 
Is an aero frame or even a full aero setup necessary for casual riding at 20mph or training? Absolutely not. Do you need it in non-competitive environments? Not in the least, if you’re riding for fun or training then your average/top speed is irrelevant. Should you choose an aero over standard round-tube frame when buying a bike for non-competitive rides? It depends - a poorly fitting aero frame will be slower than a properly fitting non-aero frame.
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Out of interest, who’s refuting scientific data?
Would say that just because something isn’t discernible doesn’t mean it’s not there. Even when sitting in a group in the draft an aero setup is saving you watts vs a non aero setup. Especially as most of us, most of the time, aren’t riding in big enough groups to get the kind of wind protection that you get in a big peloton. E.g. I do a lot of group rides but they’re typically 4-8 riders, maybe 10 tops, so you’re still catching a fair bit of wind even when not on the front (and actually sidewinds are where the aero bikes and wheels offer maybe the biggest gain).
It’s just that if you’re pushing Z1 or Z2 watts in the draft you don’t notice the same as when you’re pushing threshold or VO2 watts. Still a very real benefit though.
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I did some testing when I bought my SystemSix in 2020. I compared it to my 2014 SuperSix Evo.
The systemsix had 64 mm rims, the supersix had 60 mm, both running 25mm GP5000’s. I used the same power meter for all runs and everything was done on the same day.
I did several laps of a ~5 mile circuit with ~200 ft of climbing each lap, nothing steep. I’ll just average the results, but 2-3 laps were done to arrive at each average. Avg/normalized power about equal.
I’ll present these as follows: Body position (hoods/drops), avg power, time, speed
SystemSix:
Hoods, 198 W, 15:00, 20.4 MPH
Drops, 196 W, 14:50, 20.5 MPH
Hoods, 263 W, 12:58, 23.5 MPH
SuperSix Evo:
Hoods, 200 W, 15:28, 19.7 MPH
Drops, 197 W, 15:46, 19.3 MPH
Hoods, 266 W, 13:30, 22.6 MPH
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Thanks! Out of interest do you know what was the external rim width on the respective wheels? A lot of older aero rim brake wheels were optimised around 23mm or narrower tyres and even a 25mm used to bulge out wider than the rim which on those narrower rims would cost quite a few watts.
For the SystemSix, the external is 33 mm and the tire measured 27 mm.
For the SuperSix, external and measured tire are both 25 mm.
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Absolutely.
I honestly don’t think there’s too much disagreement on this thread, and what there is is fairly nuanced - I think it’s more about the conditions under which the advantage gained becomes discernible or becomes material to the rider. For some people, their speeds and their types of riding, the actual advantage won’t amount to that much, perhaps not even noticeable, while for others it’ll be a big deal.
+1 mph at very achievable power outputs is significant. Thanks for sharing.
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What’s your theory on the slower speed in drops vs hoods on the SuperSix Evo, whereas on the SystemSix the drops/hoods speeds were very similar (& fractionally faster on drops vs. hoods, ie. opposite to the SuperSix)?
Are your positions comparable across the two bikes?
Yeah similar setup on both bikes.
The “hoods” position was an aggressive, arms-bent, forearms parallel to the ground, position, so not upright.
Dunno, aero is weird sometimes.
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