There are several ways to figure out CDA from a race file, each with different levels of sophistication and accuracy. Some people use Best Bike split. I have heard people use winsock which I never tried. I have some tools that are not commercially available that I use. Robert's chart is a good estimator.

Better is to learn to aero test rather than rely on post race analysis.

Moving your stuff around probably didn't change your aero profile much. I suspect your fitter went for comfort over aero (unless he tested you)

I think what DD often says is "if you aren't going to test, select the one helmet that is top 3, 99% of the time". For example, a GIRO aerohead falls in that category. I think you will be hard pressed to find a person that an Aerohead tests slower than a road aero helmet. A buddy recently tested a Giro road helmet vs Aerohead and he was willing to give up a few watts for heat. He tested both one day for aero watts, then another day for heat and went for heat over aero.

Here is a chart Notio used to show how good to bad could impact speed on given watts

A lot of this will depend on the group you ride with, your relative ability to that group, the terrain and the group dynamics.

So my group is possibly the absolute perfect for me. Mostly fairly mature riders - ie in 40s and some in the 50s who are/were very very good competative riders. One of the riders is a current paralympian TT/Road race rider. And so what that means is there's no real egos in the group. We've all been there, done that, and know that no-one cares about that ride that day - no medals. So they are not bothered if I sit on the front for a long time to get my steady hard effort in, they are happy to let me, so long as the pace doesn't get too high that we start dropping people - go longer not harder is the group dynamic. We're also fortunate that the area we live has plenty of hills, so most of the time we call a 'fast' section for those and regroup at the top. And then it's great intensity training. Zwift racing is good, but I can go deeper into the hurtbox racing that last 500m of a 12km steady climb - no medals but 100% everyone wants to be first up. And again I tend to be a steady pace climber, no attacks but gradually ramp the effort. And some will try zipping off, others just hold my wheel as long as they can. Or if the paracyclist is there then I try to keep him in sight as long as I can.... And then at the end, I ride home at steady power. So that's good to do 100/120km of hard efforts, and then I finish with 20km of race pace when fatigued. Or I'll stop and do a 10km run to finish.

So as I said at start here, you can get a good workout, and actually integrate some quality into that if you use your mind and are disciplined. I think that's easier if you're at teh stronger end of the group you're in not the weaker as you get more control. I'd generally suggest being at the front of a slow group makes you stronger than being the weakest in a fast group sitting on the back in the draft and just clinging on. It's a bit counter intuitive as normally you'd say stretch yourself to get quicker, but the draft effect negates that IMHO.

Oh, one other thing, riding in a bunch will improve your bike technique and skills. You'll pace climbs better, you'll get smoother at pedalling, and of course your handling and observation skills too. All those things will make you quicker in a race.

And you end with a coffee.

Someone should label "fair," "good," "very good," and "excellent" regions on the x- and y-axes.

Yes

Excellent was supposed to be something like a .20 cda.
Fair was something like a .28. I'd have to dig up the data.

The problem was nobody had any appreciation for what .20 was.
People didn't even understand what was better .2 or .3.

Also the idea was bigger balls are less aero. The smaller you could get, the better

that's easier if you're at teh stronger end of the group you're in not the weaker as you get more control. I'd generally suggest being at the front of a slow group makes you stronger than being the weakest in a fast group sitting on the back in the draft and just clinging on. It's a bit counter intuitive as normally you'd say stretch yourself to get quicker, but the draft effect negates that IMHO.


Thanks Duncan, lots of good ideas that I can try to work in even though/unfortunately on the weaker end of this group. Totally counterintuitive, yet there is some logic to it. Funny enough, two years ago when I was just getting into cycling, a good cyclist from a well known group in my area said to me "you're not gonna get faster riding with slower people"

How about this?

As I said earlier, it is a bit counter-intuitive, and I would agree that you do get faster being pushed, but you need to use the group well. It's a bit like a staircase. Use the faster pace of the group to build your speed (the up) and then use your control to work on the endurance to hold that speed longer by not shirking in the group (the tread part). Then move up a group and repeat.