EDIT - Sorry - I didn't notice that you were specifying NON-AEROBAR bike setups. My comment below includes aerobars, so slightly different.

I do this all the time. I have a entry-level aluminum road bike from 2009 that I added clip-on aerobars to and which I still get to ride on a semiregular basis (often when my race bike is in the shop, which is was for quite awhile during the supply chain crunch waiting for parts), vs a fast Premier Tactical bike.

I used the same wheels for comparison, 88 carbon depth (although I end up racing on 88/disc on race day on the Tactical.) Same Giro Aerohead helmet and same triathlon suit. I ride 3 main loops a lot, so I know really well what my power and speed should be on them for each bike. The only small caveat is that my position is close but not identical between bikes, mainly because of one is a road, not TT bike, but I'm equally low on each.

I'd estimate about 3-4 minute difference on a 2 hr loop for the road bike+aerobars vs my TT bike. Like 2:00 vs 2:03-2:04. Yeah, not a huge difference, but it's a difference. 1-2 mins on a 1 hr loop.

So you're definitely in marginal gains territory with these pricey frame upgrades. Still, riding a hot new TT bike is really fun, and you gotta try it to believe it.

The upgrade that made the biggest difference for me was a wheel upgrade. My upgrade was from the stock 'training' Shimano wheels with butyl tubes that my road bike came with, so going from that to latex 88/disc was huge - huge enough to take me from my typical top 15% in a local Oly race to the having the fastest bike split after the upgrade, around 6-7 minute improvement over an hour. In a 2 hr training ride, it's about a 10 minute time gain when comparing race wheels+latex to no race wheels. It's such a big upgrade that I can't agree with the prior information I was seeing online that wheel upgrades are just 'marginal gains' - they are literally such a big factor that it's impossible to compete with the top guys even at a small local race without them. (Most calculators online said I would need to generate like 80-120 watts more power to get the equivalent speed gain on training type wheels, which is impossible for most people.)

I mean it's pretty cool that some of us already did that. https://drive.google.com/...w1E3t2fUwReMyDr-8B0Q

In the old days the bike was ~ 15% of the total drag package (call it 12-20% depending how well or not you were set up). Now you can shrink that by 2-5% (again depending on how well you're set up). Which makes positioning, clothing, helmet choice even more important. Today's bikes just do a such a good job integrating everything, hiding cables and making adjustments easier vs 10yr ago.

I did some very informal testing on my scott plasma 3 which was heavily modified (drilled out the frame to run electronic shifting internally, added tririg bars & front brake + extensive wind tunnel testing) and my modified P3x which had a P5x front end on it. FWIW My plasma was as fast as the tactical in the above paper. (actually at 0 yaw it was slower than at 2 of the above tested yaw angles it was faster and slower at the other.)

On the flats the P3x was ~ 5-7w less than my Plasma to go the same speed or about 1 maybe 1.2mph faster for the same watts. very informal testing though looking at averages over multiple sessions on the same rectangular like course. Climbing though I think the P3 was slower, it did not feel as good climbing that's for sure, not that the Plasma was a climbing machine

hope that helps. lmk if any questions

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

One of those isn't right. A 2.5% change in power would be ~1% change in speed... unless you were going so slow that Crr dominated, or climbing steep hills where they would trend closer to the same effect.

For 240W and 25mph a 6W change would be ~0.25 mph.

Definitely some confounding variables there, besides just the wheel design.

Like I said informal. Not head to head.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

If you aren't saying that 5-7W are equivalent to 1-1.2mph, then what are you saying?

If I am interpreting the OP’s question correctly, they are asking about comparing 2 road bikes. ie a 2010 Specialized Allez (the round tube non-sprint version) vs something like the new Madone

While I am a fan of the aero shootout and the work you guys did, not sure how much of it would apply I’m this question that is comparing bikes that were already optimized for aero in their tube shapes and what not based on the knowledge and tech at the time.

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Matt

I have a '19 Cervelo R5, rim brake version. It's not an aero bike, per se, but the shaping of the massive downtube seems like a really big Kam Tail shape. :) It rides really nicely, stiff and light and all that...

I also have a '02 Litespeed Classic, pretty much an old school round-tube'd Ti bike. Modern parts on it, but nothing fancy at all about the tube shaping.

For all I can tell, there are really only two differences, one of which can't be quantified. On multiple rides on various routes that I ride frequently, the elapsed time works out roughly the same, on average, for a similar power and RPE output. The Litespeed is significantly more comfortable to ride, even with the same wheels at the same pressures as the Cervelo. I have the contact points set in the exact same position, so it's not about being more or less upright, or whatever. Some of it is geometry (the Litespeed has slightly longer chainstays and quite a bit more trail, so it's more stable) and some of it is just 'feel'. As for 'feel', the Cervelo certainly feels like a race bike. So, the subjective feel of the bikes is different.

Quantitatively, however, it is much easier to crank out a max sprint on the Cervelo. But, that's the only scenario I've found where the increased stiffness of the frame is a plus.

I should not have used the word testing. I did not say 5-7w are equivalent to 1-1.2 mph. What I should have said is I noticed that the p3x seemed to be 5-7w faster at some times and around 1 to 1.2 mph faster at other times

I distinctly put ~ in front of the wattage, used the word informal as well as a range of a few tenths of a mph to indicate the uncertainty within.

It's more of a hey here is what I noticed on a few rides over the same course on different days.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta