I agree for the most part. All I’m getting at is that it’s easy for people to become discouraged because they don’t have the perfect tool for the job. Obviously one setup is faster but it’s still doable and maybe competitive if you only have a road bike.
And reference my ride, It’s impossible to compare watts. I’m not very big and have a decent amount of experience riding and staying in aero positions. Watts don’t win races. Power meters are also not exactly consistent among each other.
Absolutely all in favour of using what you’ve got! Did my first ironman on a road bike with clip on aero bars, shallow wheels, Conti gatorskins, etc and had an absolute blast 
. Then actually did some research, bought a secondhand TT frame and built it up myself on the cheap and tested some different positions with the incredibly scientific “rolling downhill and seeing how far you get” method, knocked over an hour off my bike time the next IM for similar RPE/HR/fitness (no power).
@PawelKozel said he was planning on buying a new bike for the race though so I’m guessing there’s budget for a tri bike.
All the attributes of TT/tri bike (aero frame, aero bars, aero wheels) come with a caveat - it’s all based on an average speed of 40kph. Outside of pros and top tier age groupers, that’s not realistic. Add in the fact that most TT bikes are heavy, climb poorly, corner poorly, descend technical descents poorly (compared to a road bike), and the shininess starts to fade. Sure, on a pan flat course like Texas or Florida, there’s some advantage, but take IM Switzerland, with lots of climbs and technical descents (in pouring rain when I did it), and the road bike has an advantage. I see triathletes waste thousands on Tri bikes expecting instant speed, but lose all that advantage due to poor riding skills, or crashing b/c their head was down and they pull a Bernal.
This thread is so odd, what year is it!!!
IMHO
TT bikes are def a horses for courses thing, but the slower you are the more time benefit you gain from improving aerodynamics.
Going slower you gain less total watts benefit, but due to the additional time on course your total time savings go up.
Top work! 
Boo!
You have a point but come on; reads thread, wonders about it, jumps on bike for 4hrs, and gives us the answer.
Hi @JoeX ,
I was looking at this type of videos
Yeah, I’m just trying to ‘quantify’ the advantage that seems a bit too small to me (or ‘unproven’) although with all your argumentation and opinion I’m getting outside, indeed everybody is hell bent on - tri bike is really faster than a road bike with aero bars. So I’m lost 
If you are just wanting to have the debate for the debate sake just say so, I feel like you are trolling a bit now ?
Did you watch the video? she saved approx. 48 watts between her road bike position and the position with clips ons, and then another 6% (3 watts) when she switched to the dedicated TT bike.
The caveat in that video is that she used the same position on both the road bike with clips and the TT bike in a wind tunnel. Most riders do not have that option (wind tunnel) nor are road bikes easy to get that low of a front end as in the video. Most of the time you add clip on bar and they are sticking up above your drop bars and get this bodged half tri bike half road bike
Not trolling at all ! Sorry if that’s what it looks like - I’m just looking for as much of objective numbers as possible.
And yes, of course I did watch the video - the real comparison is between road bike with aero bars vs TT bike. And as you said, the difference comes out at 3W for her.
The video you’ve linked has some caveats that explain the confusion;
“ We can’t ignore the fact that the AIR is not a ‘standard road bike’ - it has been designed to be tinkered with and taken very close to a TT ready rig, with a four-position seat post. This allowed for effectively a 76 degree seat position and a low front end on the X-Small road bike I was aboard”
Ultimately they got the same positions for the rider on both bikes which is not going to happen for most riders and their bikes.
It can be confusing as many people do fine with clip ons and feel it’s a massive investment to get a tri bike. Some of us have tried clipons and moved on to a tri bike and know the benefits first hand, so we’re a lot more comfortable with the message.
On the side bar for that video there are many other videos, with the more conventional message. My own opinion is that there is a lot of money behind the “aero road” bike marketing.
Quantifying benefit of attributes of our hobby tools and trying to perform a cost.benefit analysis is a fools errand, and ultimately you will just do what you want to. So I say use the bike you like - and the red ones go faster. 
I would say most find it challenging to get great tri position on their road bike. Getting that low of a front end as in the video, in my opinion she gets there pretty easy because of her size and that bike. If you are tall and your bike has a high headtube you are not so lucky.
you will see her bars in the video are under the drop bars which is unusual, for her its only three watts, but she is going from a great position to a great position. She isn’t the norm.
I agree with @JoeX - above - however I am leaning more toward purple these day (that new Cervelo S5 in Sapphire Ice - whooo take my money)
100% this….most people think “oh, I’ll put clip-ons on my road bike and that will be close enough”.
Nope…not even close. It is better, but doesn’t come close to a full Tri bike setup. Again, go play with Best Bike Split if you want an “objective” number.
Back in the day, I set up my Cervelo S2 as a Tri bike and got into a great position….but it wasn’t easy. I had to use the reversible seatpost, and eventually got a 120 stem that was -30*. I also had a full TT bar setup. In this configuration, I was probably losing nothing over a dedicated Tri bike….but again, it took effort to get there.
ETA - I can’t get the link to my pic to work from my iPad. I’ll post the pic later.
Interesting Slowtwitch article HERE about seat tube angle as it relates to this thread.
TLDR steeper STA’s FTW.
By now you should know the limitations, though, because many people with experience have repeated them here:
Rather than talking in circles, you could tell us:
If the answer to the first two is no, you should really try to rent or loan a TT/tri bike to see what they feel like. If the answer to the last one is no, you should know that you are leaving some speed on the table, too.
To me the idea of clip-on bars is that you can use your road bike for two tasks. The more changes you have to make — and putting on an extreme stem, TT bars, TT shifters and brakes, etc. defeats that purpose.
Support for Aero bars on gravel/road bikes. The only difference is you don’t need to run off the bike. But as far as on the bike effectiveness I think anyone would want aero bars for solo efforts. The question needs to be re worded: Road bike with aero bars vs Tri bike speed. I’ve done them all and know what’s fastest for me in every situation. You guys need to figure it out for yourselves. Enjoy
I am a little confused what you want to say here: nobody is denying that using aero bars during long endurance races doesn’t come with aero benefits. It is a matter of optimization: you wouldn’t want to ride a gravel race on a hypothetical TT/tri bike with wide gravel tires on it. Handling is severely compromised on a TT bike, something you need for some sections at least. Putting tri bars or togs gives you an additional position, but the bike setup isn’t designed around the assumption of you being in the aero bars.
The bike stint of a triathlon is quite different: here, you want to be aero as much as possible, bike handling and other things come in second.
Thank you all for some excellent answers ! Will most probably buy a tri bike now
PS. Still disappointed though at the lack of data and experiments on that - this should be easier. Dumb idea - crowd-testing - one could publish some testing protocols and people add their results (a bit like hardware testing, but obviously with a human factor). Like - people who have both, a tri and road bike with aero bars, upload results for a 10km ride in such conditions etc etc. I would think that with hundreds of people, we should see some interesting results.
Oh yeah…100%. That was what I was trying to o convey. I was able to do it, but it took a concerted effort to do it. It was not just as simple as slamming on some clip-ons and thinking I was aero.
But I did have online cable adjusters / splitters between the HB and the frame. I had my road HB setup with full length cables / front half housing to match the adjusters. I could swap between the two setups in ~20 minutes. But it was still a total PITA.
I don’t know why you have that impression. There is all kinds of data out there on this subject. Again, Best Bike Split can give you the differences.
Or go over to Slowtwitch and ask the question there….you will be deluged with data on the subject.
(Just kidding…don’t go there. That place sucks and reeks of attitude and entitlement. 
)
If you think about it, you will quickly realize that it is not at all easy. The reason is very simple: as of now there are no good, commercially available solutions for measuring drag. Some companies are working on it, and might release something in the next few years, but even then, it is early days.
And even then, a lot is about finding the right position. You really have to train yourself to be comfortable in that position for 5–6 hours, which again is quite different than, say, a TT setup where you need to be comfortable for 15–60 minutes.
The data will almost invariably be useless to you. You will have people who just put on clip-on aero bars without altering their road bike setup. Others might go in whole hog to build a tri/TT bike on the cheap, complete with proper tri bars that replace your handlebars, new shifters and brakes, etc. The results won’t be comparable at all. Instead, I reckon you’d get a very wide distribution with lots of noise and a large confidence interval.
IMHO I’d approach the topic from a very different direction:
With hydraulic brakes and/or internal cable routing, changing your setup might take even longer. I can totally see someone building up a used road bike as a cheap TT or tri bike, though.
Also, getting your setup just right every time would test my patience. Just getting handlebars really straight is something that drives me up the wall. Not to speak of saddle position and saddle height.