Tell me your CdA reduction stories!

Triathlon Forum
1

Hi all, I’m about to embark on some self testing and have been pondering what other people’s stories may be in the hunt for a lower CdA! I know this is individual to every rider but I thought it may be interesting to share your own findings.

Things like:

Where did you start at and where did you end up, eg started at .25 ended at .22.

Was there a small change that made huge impact?

Was there a change that made a reduction that you weren’t expecting?

Was your lower CdA position harder or easier to hold?

Feel free to add some more! I will share my own when completed!

2

I started around 0.27 and went to an aero camp at ero with Jim and Desert dude

Next year, went back to A2 with desertdude.

Between those visits, building some 3d printed risers for my ia and some testing on my own, I’ve gotten down to high 0.21s (but really, I’m bad at keeping my head down, so probably race in 0.22 land)

At daytona,(56 mile) I rode a 2:15 on 190w (im 6ft, weigh 173 or so)

Switching to 165 cranks opened up a ton for me

3

Nice work! What were the main changes you made to get down to your lower number?

4

Lower front
New helmet/kit
10 degrees of tilt on arms
More reach
Rear hydration actually tested a bit faster
Shorter cranks made me more able to hold the new position different shoes
Different pedals

(off the top of my head)
.

5

Not much to input here other than I like this idea. Good post and looking forward to what others share.

6

I started around 0.27 and went to an aero camp at ero with Jim and Desert dude

Next year, went back to A2 with desertdude.

Between those visits, building some 3d printed risers for my ia and some testing on my own, I’ve gotten down to high 0.21s (but really, I’m bad at keeping my head down, so probably race in 0.22 land)

At daytona,(56 mile) I rode a 2:15 on 190w (im 6ft, weigh 173 or so)

Switching to 165 cranks opened up a ton for me

How does .22 CDA get to 25 MPH at 190 watts

https://www.endurance-data.com/en/cda-calculator/

7

Sorry,
I always think in my 0 degree yaw cda.
After the weighing and wind best bike split has the average on the day closer 0.20

I also don’t have a ton of recent races… Knee surgery 2 or 3 years ago (and covid before) means I just have small sample as of late.

8

I started around 0.27 and went to an aero camp at ero with Jim and Desert dude

Next year, went back to A2 with desertdude.

Between those visits, building some 3d printed risers for my ia and some testing on my own, I’ve gotten down to high 0.21s (but really, I’m bad at keeping my head down, so probably race in 0.22 land)

At daytona,(56 mile) I rode a 2:15 on 190w (im 6ft, weigh 173 or so)

Switching to 165 cranks opened up a ton for me

Not to diminish from your achievement, but Challenge Daytona (if that’s what you mean), is not a good benchmark at all since you are riding in the center lane with cars going next to you and creating a lot of pull. I did very similar numbers (2:17 on 190w) and I don’t think I’m anywhere near 0.22 CDA

9

I tested in November 2022 - on the track in Copenhagen. 13 runs - testing helmets, suits, calf sleeves and position.
And January 2024 with WattShop in England - 1 day on the track and 1 day in the windtunnel.

It’s hard/impossible to compare Cda values, but it’s talk watt savings instead @45km/hr :slight_smile:

Giant Trinity (same bike in all tests) with Cadex Wheels - GP5000 TT TdF tires.

Baseline in 2022 was Trimtex standard LD suit and Giro Aerohead helmet. Velotoze calfsleeves and Giro Empire with laces.

Baseline in 2022 - 303 watts.
Final result in 2022 - 290 watts (Met Drone, Box on chest, Castelli Suit, HUUB 2.0 sleeves, saddle height -2 cm, +4 cm reach and +2 cm stack)

Savings in 2022 - 13 watts.

And again the absolute numbers from 2022, can’t be compared to the numbers from the test with Wattshop.

Baseline in 2024 on the track: 261.3 watts.
Changes made during the 17 runs: Wattshop extensions, 25 degress angle on extensions, going from ISM to Pro saddle, 15 mm more width between elbows, BTA, saddle down 10 mm. Also tested Camelpak in the suit and bottle behind the saddle - the BTS was neutral for me and the camelpak was 4 watts - but now illegal.
Numbers after all the changes: 247.3 watts.
Savings day 1 in 2024 - 14 watts.

The numbers was then the new baseline tested at the first run in the tunnel: 280.8
Changes made during the 24 runs: Specialized TT5 helmet, HUUB Plus 22 suit, bigger BTA bottle
Numbers after all the changes: 268.1
Savings day 2 in 2024 - 12.7 watts

Almost 40 watts over the 3 tests. Windtunnel also confirmed some of the findings in 2022.

Will I go to the windtunnel again? Only if I win the lottery. The track? Yeah - I think so :slight_smile:

10

good post
cheers
.

11

Was just trying to participate :). Really didn’t mean to make it a thing.
Also happy to share the tunnel uploads. I Have no reason to make stuff up.

12

That’s some great optimisation! So higher and longer stack with a lower saddle height was fastest? How does that feel compared to where you started from?

Was there anything you tested that was instantly had a negative impact?

13

Lower and more narrow was slower.

I’m more comfy than my original position, and I can push more power.

Next thing to test will be shorter crank arms - 165 mm now and then lower the saddle and lower the front. And maybe 2 or 3 bottles between the arms.

14

I guess that’s a dream result, comfort, power and faster! Great story.

15

Was just trying to participate :). Really didn’t mean to make it a thing.
Also happy to share the tunnel uploads. I Have no reason to make stuff up.

I am sorry, did not mean to attack you at all.
My point was that CdA numbers may not be so relevant as benchmark, more relevant is the relative improvement (which you seem to have done well).

16

Was just trying to participate :). Really didn’t mean to make it a thing.
Also happy to share the tunnel uploads. I Have no reason to make stuff up.

IIRC we were testing together in 2016 at Ero. We were testing 2 at a time and I am pretty sure you were my lane mate. Glad to see someone stick to it with very tangible results

17

I started around 0.27 and went to an aero camp at ero with Jim and Desert dude

Next year, went back to A2 with desertdude.

Between those visits, building some 3d printed risers for my ia and some testing on my own, I’ve gotten down to high 0.21s (but really, I’m bad at keeping my head down, so probably race in 0.22 land)

At daytona,(56 mile) I rode a 2:15 on 190w (im 6ft, weigh 173 or so)

Switching to 165 cranks opened up a ton for me

Not to diminish from your achievement, but Challenge Daytona (if that’s what you mean), is not a good benchmark at all since you are riding in the center lane with cars going next to you and creating a lot of pull. I did very similar numbers (2:17 on 190w) and I don’t think I’m anywhere near 0.22 CDA

I’m 6’ did 241 watts 2:19

Thinking I really need to focus on getting more aero

18

If you have time to kill, here is one guy’s journey

https://cyclingtimetrialpodcast.libsyn.com/175-marc-graveline-testing-sylvan-adams-to-a-world-time-trial-championship
.

19

holy cow just doing tempo on a loop i realized i’ve assumed its normal to require 300 watts to do 40km/h. and i’m quite small.

i’m guessing a lot of this is helped by bike adjustability. mine is a pain to change stack and seat height (slips) on, so i’m hesitant to mess around with it. but that hesitancy is probably costing me serious time.

this might be a good argument for caring about ease of adjustment, even for those of us that don’t fly much. just being able to iterate and test.

20

holy cow just doing tempo on a loop i realized i’ve assumed its normal to require 300 watts to do 40km/h. and i’m quite small.

i’m guessing a lot of this is helped by bike adjustability. mine is a pain to change stack and seat height (slips) on, so i’m hesitant to mess around with it. but that hesitancy is probably costing me serious time.

this might be a good argument for caring about ease of adjustment, even for those of us that don’t fly much. just being able to iterate and test.

Actually, having your own World Tour mechanic with you helps a lot more LOL