So I’ve had a merida reacto for about 4 years now and I really like it. Just for kicks I decided to build a steel frame bike up. So I found a genesis Volare, built it up with spares I had and second hand bits of ebay.
I’ve been out on it today on one of my usually loops and low and behold it’s no slower than my reacto. I know there are lot of variables, wind etc. However this is real world riding and beginning to think for mere mortals aero bikes don’t make much difference. Anyone else have real world examples?
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I went from a 2018 Orbea Orca - nothing aero, to a 2023 Polygon Helios, all aero. I was hitting strava segment PB’s left and right. It definitely made a difference. My terrain is flat, hilly, coastal and windy. I’m easily 1+ mph faster on the average ride. I did not do any back to back comparisons as my aero bike was a replacement of my stolen bike. It was so obvious to me anyhow.
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Assuming everything else is equal (position, clothing, power output, wheels, tyres) then the frame itself doesn’t make a huge difference. Small enough that it maybe gets lost in the noise when comparing 2 rides on the different bikes - e.g. Weather conditions or small differences in power meter measurements could have a bigger effect. If in a group ride it will be even smaller. In a high speed solo effort like a TT I can definitely see the speed difference in the data though.
If I had to put a number on it then having done a few TTs on both my aero carbon bike and my round tubed titanium bike (same position, same depth wheels, same tyres wren in race setup) the aero bike tends to be about 0.3-0.5kph faster for the same power at ~40kph. Maybe a little more if it’s a more technical course, but I think that’s because that bike is also lighter and stiffer so has more of an advantage if I’m having to brake and accelerate.
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My personal experience is that with an aero bike (and all other ‘aero’ stuff) it’s a combination of various items working in unison that makes a noticeable difference.
Any single thing on its own is just impossible to reasonably discern out on the road with any real accuracy (acknowledging that ‘feel’ does indeed count for a lot).
For example, as already mentioned, travelling at average Joe speeds (let’s say for example 20mph) then just an aero frame on its own compared to a so-called non-aero frame may produce minimal / tough to even notice gains for an average rider who maybe sports an ok-ish aero riding position most of the time / some of the time.
However, again as already mentioned, it is quite possible (probable?) that an aero bike will not only have an aero frame, but also deeper / wider aero wheels, and if reasonably specified may also have higher quality hubs, with lower friction bearings, and maybe higher end road tyres, and maybe aero bars and perhaps a more tidy or enclosed cabling setup etc.
All of those things combined, would perhaps more likely become noticeable.
Then add in higher speed (for example 30mph on a concerted TT effort) and it becomes even more apparent.
Then add an aero road helmet, tougher fitting kit or a skin suit, aero socks and gloves and shoe covers etc. and the compounding of all these separate small sub elements adds up to an even more noticeable difference.
If the aero bike is relatively ‘new’ and the non-aero bike is relatively ‘older’ then frame weight might also be a factor, that impacts speeds at least a little, on anything other than pan flat roads.
Finally, adopt a more ‘aero’ position, which perhaps a more aggressive aero bike may force you into compared to a more relaxed frame geometry and that adds another layer.
I imagine that as already mentioned, actually trying to pinpoint a material difference out on the road for any single item (such as a frame) is super difficult, given the high number of uncontrollable external variables, but add a reasonable number of the aforementioned elements together and you perhaps can tell the difference.
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The more efficient you get, the more efficiency matters. Or another way to say it, the less watts it takes to hold a given speed, the more aerodynamics matter. Watts savings isn’t static or even linear, so the faster you are able to go for a given power output, the greater the potential savings of aerodynamic clothing, frames, wheels, etc.
Assume you have a 300 watt ftp. If you are rolling on box section wheels, gravel tires, non aero frame, baggy tee shirt, cheap helmet, very upright, and weight 100 kg, it may take 300 watts to go 20 mph. An aero frame may only save 5-10 watts at 20 mph. If you have a maximized position, weigh 65 kg, with all aero gear, 50-60mm carbon wheels, race tires, etc you might be able to hold 26 mph at 300 watts. The aero frame in this scenario might get you a 20+ watt gain. The more aero and efficient the system becomes, the greater drag the least aerodynamic component or part has.
If your average speed is 16 mph, I’m not surprised an aero bike doesn’t help. At 26 mph, it’s likely a pretty massive gain, with the caveat that the rest of the system is actually efficient. If it takes 450 watts to go 26 mph, then the likelihood of seeing much gain is still low. If it’s only 250 watts, then the aero frame should yield dramatic speed improvements.
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Yeah that’s my point, Mere mortals who are riding 16 to 20mph I’m beginning to think aero dynamic frames don’t make a discernible difference.
I think many of the view points here are salient but I come at it from a slightly different angle. Often if you feel fast you may actually be faster, this can come from so many places, many of which have been mentioned. Also in the Strava era, chasing down mere seconds to claim KOM status on a given segment may be of value in which case an aero frame is a definite positive. I have owned more than one of each type, aero and non aero and personally feel an aero bike is faster in nearly all circumstances as long as the gradient isn’t above about 6%. This is of course where speed is the overriding concern. If getting out, riding with your friends or some form of less competitive riding then no an aero bike is not advantageous. It really depends how you view it and what you like.
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Come spring I’ll wait for a calm day and do a loop with both bikes using the same power meter pedals and see what difference I get.
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Wait, you lose a third of your body weight to get the gains? 
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As a complete opposite example, I was riding my Specialized Crux for about 6-7 months as my dedicated road bike. We were moving so I had downsized my stable to have less to travel with (plus gave me an excuse later to buy a new road bike). Had my deep section aero wheels on it for most rides as well. Then I bought a Cannondale SuperSix Evo. Every ride had 10-15 PRs on Strava segments. Faster on every terrain. And I wasn’t pushing it going for segments, the SuperSix was just faster and more aero.
One ride is hardly evidence. Not to mention you’re on a new bike, so you may unconsciously be pushing a little harder because it’s new and different. Or wind.
I tested a 2024 road bike, aero frame, disk brakes, 50mm wheels, hidden cables, ceramic bearings, oversized pulleys, Ultegra Di2 against a Focus Izalco from 2015, rim brakes, 21mm wheels, exposed cables, mechanical Dura ace 9000. Both bikes had the same 38cm bars and the same tyres. The Izalco is 1.5 kg lighter.
I did 24 runs on a flat 2km segment, alternating with each bike. I used Assioma pedals power meter which I calibrated before each run and I rode at a constant power of 270W. So 12 runs with each bike at approximately 40 km/h.
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No it’s not evidence but what I mean is we are fed a narrative that aero bikes save this that or the other when in reality unless you’re competing, particularly in time trials then the difference between aero and non aero bike are marginal at best. Just my thoughts. ride the bike you like
And the conclusion?
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Well then I have to say it’s an odd point for you to make a whole thread about. It just seems like you’re trying to rationalize not wanting an aero bike. They’re faster. They’ve been proven faster. I and others here have data that show they’re faster on our everyday non racing rides. If the round tube steel bike is better for you, cool, ride what you like. I like going fast. It doesn’t have to be a race. Fast is fun. It’s not marginal, it’s noticeable. That’s fine if that’s not the case for you.
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Honestly, I’m tired of the aero denier attitude you find on forums. Aero is not some conspiracy foisted upon us by the industry.
There have been so many tests by reputable people that it’s pretty clear that aero gains are real. In some cases, it’s a big difference. And in many cases, it’s just a small difference.
AFAICT, ballpark saving are along the lines of:
Wheels - low profile, box section to aero wheels - save about 20-25 watts
Frame - non aero round tube frame to full aero frame - 10-15 watts
aero bars / cockpit - 3-5 watts
aero helmet - 5 watts
So, you go from your old, old bike with no aero features to all the aero features, then it’s quite a big gain. 30-40 watts is very meaningful if you race or even if you go spirited group rides and want to perform.
Now if you have a 5 year old aeroish bike with aero wheels already, then any upgrade you do is going to be marginal at best.
Likewise, if you go from your 10 year old Zipp 303s to some fancy modern wheels, any gain is going to be in the neighborhood of a handful of watts. Not much.
Similarly, since the frame itself only yields a 10-15 watt improvement for a significant investment, it’s usually not worth upgrading just to get those few watts.
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In an average June or July when I’m in decent form, I’d need to spend several hours each week for a month or two trying to gain an extra 10W, or get an aero bike …
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Can you post the data for the runs?
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I own an aero bike
Out of 12 runs, the 2024 bike was faster on 3 runs. The Izalco was faster on 6 runs. 3 runs were the same. The overall average speeds were identical.
I also did the same test last year on the 2023 version. Out of 14 runs, the 2023 bike was faster on 6 runs, the Izalco was faster on 6 runs and 2 were the same.
These are real world conditions with wind and a small amount of traffic (one or two cars per run).
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It seems like 2km is not very far to suss out the differences. Also, from what I can tell, it’s very hard for an individual to do these types of tests really well on open roads. To do a good job, it seems like one would need an aero sensor and maybe do it on a velodrome.
The German magazine Tour is famous for their aero bike tests. One thing that stuck out to me was that the time savings from a non aero bike to a full aero road bike was on the order of 3 minutes over 100km. That would be 1.8 seconds per 2km which is hard to measure.
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