A good CdA for bike and rider is ~2200 cm^2. Non streamlined shapes have a Cd of ~1. How many cm^2 of frontal area are we talking about?

This seems silly, but given this is a TRI forum......I think it needs to be specified more often whether this is for TRI or for TT when asking a question.

I prefer watts for TT, time for Tri.

Almost none of us get to the speeds the wattage numbers are quoted at, but all of us can benefit from the time savings over longer periods of time.

This would be especially useful for something like eliminating a FD. The time would be much more useful than what almost adds up to "statistical noise" when it comes to the wattage savings at a realistic speed.

Think of it this way, if I give you only a minute or two to count out grains of sand it won't look like you've got very much. But if you're given several hours, at the end you'd notice a bit more for your efforts.

To be helpful, here are the links:

1-4 watts here:
https://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/1x_aero_gains_P6190009/?forum_view=forum_view_collapsed&


3T release info:
https://blog.3t.bike/2018/07/3147/introducing-the-strada-due/

In my case, on a IM course, 1 watt is roughly equivalent to 1 min.

I know that not all cm2 are equivalent otherwise internal cable routing will be a smaller concern than getting making very narrow tube.

Unlike aerobar or frame, for that part of the bike, there should be less controversy of fit over design, if it make any difference.

I'm looking to upgrade my bike, and i'm wondering if choosing a different drive train could make a difference

But i appreciate that it's something that will be hard to test

CdA is the universal aero drag value. It is not effected by speed or air density. If you'd like to translate CdA into watts or time, and you don't want to calculate it precisely, there are rules of thumb to get you in the ballpark. I strongly encourage you to become familiar with CdA.

The example I gave is actually a good way to think about drag, and get a feel for how much different things *could* matter. If you know your CdA is 2200 cm^2, and a 10cm^2 "block" is sticking out in the breeze, that's 10/2200 = .0045 (.45%) of your total. A good ROT for converting that to time or speed is to divide it by 2.5. So you'd be .45/2.5 or 0.18% slower.

 
Actually: It is a product of an objects drag coefficient (Cd) or "slipperyness" and it's size, criticaly it's frontal area (A).
https://www.cyclingpowerlab.com/CyclingAerodynamics.aspx


Not all cm2 of frontal area are equal, otherwise nobody will be buying deep section wheels, and nobody will be making a big deal on racers using gels to go faster... (change the slipperyness)

My Pioneer is definitely adding an extra 10 cm2 (in certain angle)... which is more that the difference between go and bad pedal / cleat selection (+/- few watts). Just not sure if it actually mater given all the extra movement.

Well the pod on the Pioneer actually fills the hole in the spider. If you look at the CFD images in the aero shoe thread you will see the the spider is a high drag/preassure area. You usually reduce Cd when you round or close off flat surfaces. Your PM may be actually be reducing drag. Now the safe bet for a marginal gain is a powertap hub PM, and aero crank, Speedplay aero pedals , 1x drivetrain, and some smooth lace up shoes. Will this be a big savings? No idea, but there are reports of more that a couple watts saved from any of these single modifications and each one of these items is hideously un-aero. It is probably a safe bet.

I know, that's why I said I was referring to non-streamlined shapes that have a Cd of ~1.

There is an error in that link regarding airfoils. Bicycle parts are in the subcritical Re# regime where streamlining offers only modest improvement. Cds of ~.3 to .5 are more realistic.

Where your powermeter or other parts on the bike are concerned, the addition to frontal area is the most important consideration. And if the area isn't large, then it isn't going to effect your drag very much.