Real World Aero Test Bianchi Inifinito v Cervelo RCA

Discuss light weight issues concerning road bikes & parts.
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sethjs
Posts: 101
Joined: Fri Feb 04, 2011 4:02 pm
Location: San Francisco, CA

by sethjs

So my very understanding wife helped me run a pretty interesting aero test this AM on the two bikes above.

Location: San Francisco Golden Gate Bicycle Track
Methodology: Test each bike at 300 watts, roughly 6 laps each (1km / lap), split as 3x2. Swap wheels (Roval CLX 50, Specialized Turbo 24mm, 80F90R) across bikes. Same clothes. Same weather. Positions as close as I can get them. Even swapped saddle bag, lights & computer between the bikes for each run. Did 2 runs each. Infinito. RCA. Infinito. RCA.
Conditions: Winds: Light & Variable. First two runs were at 55F. Second two at 59F & 61F. Very light lap traffic - mostly just clean air.

Net: Looking at the data, it'd appear the Cervelo is approx 1 second faster pretty consistently. Strava links below. The best segment to look at is the "GGP Polo Field Lap" segment. And the times between 1:39 & 1:44 are the segments where I was at power.

As you all likely know, the Infinito's really not meant to be an aero bike in any measurable way. The RCA is supposed to be quasi-aero.

Comments / thoughts welcome.

Bianchi 1: https://www.strava.com/activities/1497075391
RCA 1: https://www.strava.com/activities/1497146670
Bianchi 2: https://www.strava.com/activities/1497223161
RCA 2: https://www.strava.com/activities/1497256177

by Weenie


cassard
Posts: 95
Joined: Wed Jan 24, 2018 12:31 am

by cassard

that's nice to see people doing those tests !! what is you did is a simplified version of a classic linear regression method testing for aerodynamics. The method you used is pretty good, really nothing much to say about it.

In the futur, if you want to have more fun doing this kind of testing and you want to be a bit more rigourous, this is what you could do.

- Do the testing with the speed as the independant measurement and notice the watts differences. You can do let's say 6 to 10 runs of 2 laps at 40km/h (25mph) and compare the watts needed in between both.
- Take the atmospheric pressure in consideration (mostly weather apps or website will tell you).
- keep the same position or even try different ones.
- Finally, if you want to get really technical, you can even tke your CSV file and build a linear function and find your Drag coefficient.

Props !!

tabl10s
Posts: 219
Joined: Wed Aug 23, 2017 5:40 am

by tabl10s

sethjs wrote:
Mon Apr 09, 2018 12:21 am
So my very understanding wife helped me run a pretty interesting aero test this AM on the two bikes above.

Location: San Francisco Golden Gate Bicycle Track
Methodology: Test each bike at 300 watts, roughly 6 laps each (1km / lap), split as 3x2. Swap wheels (Roval CLX 50, Specialized Turbo 24mm, 80F90R) across bikes. Same clothes. Same weather. Positions as close as I can get them. Even swapped saddle bag, lights & computer between the bikes for each run. Did 2 runs each. Infinito. RCA. Infinito. RCA.
Conditions: Winds: Light & Variable. First two runs were at 55F. Second two at 59F & 61F. Very light lap traffic - mostly just clean air.

Net: Looking at the data, it'd appear the Cervelo is approx 1 second faster pretty consistently. Strava links below. The best segment to look at is the "GGP Polo Field Lap" segment. And the times between 1:39 & 1:44 are the segments where I was at power.

As you all likely know, the Infinito's really not meant to be an aero bike in any measurable way. The RCA is supposed to be quasi-aero.

Comments / thoughts welcome.

Bianchi 1: https://www.strava.com/activities/1497075391
RCA 1: https://www.strava.com/activities/1497146670
Bianchi 2: https://www.strava.com/activities/1497223161
RCA 2: https://www.strava.com/activities/1497256177
Deleted
Last edited by tabl10s on Sat Apr 28, 2018 6:02 am, edited 1 time in total.
2016 Orbea Orca OMR:

15.2lbs(6.89kg).

2013 Wilier Zero.7:

13.65lbs(6.19kg).

2016 Rca:

12.02lbs(5.450kg)

2015 Pinarello F8(build in-process).

quadzilla
Posts: 13
Joined: Thu Dec 21, 2017 7:42 am

by quadzilla

what was the wind like? I ride at the polo fields every week and usually there is a pretty strong headwind on the bleacher straight and strong tailwind on the sprint segment. I've tried to do testing but ive also found that the wind is inconsistent. Yesterday I did a 4 lap pursuit on my road bike and on the bleacher section to hold 26mph in "invisible tt bars position" it took me ~330-350 watts while it only took ~250 on the tailwind section.

edit: looked at your power seemed reasonably consistent. Just wondering if it was breezy.

User avatar
jekyll man
Posts: 1366
Joined: Wed Apr 25, 2007 10:23 am
Location: Pack filler

by jekyll man

How did you measure speed/distance for accuracy?
GPS or speed sensor?
Official cafe stop tester

prebsy
Posts: 764
Joined: Tue Oct 23, 2012 10:52 pm
Location: PHL

by prebsy

Use aerolab in golden cheetah, a la chung method and like CASSARD said you don't need to control the power just observe.

sethjs
Posts: 101
Joined: Fri Feb 04, 2011 4:02 pm
Location: San Francisco, CA

by sethjs

quadzilla wrote:
Mon Apr 09, 2018 6:04 am
what was the wind like?

edit: looked at your power seemed reasonably consistent. Just wondering if it was breezy.
It varied from essentially none to a slight detectable wind from the west. But it was early morning, so generally speaking, light winds.

by Weenie


sethjs
Posts: 101
Joined: Fri Feb 04, 2011 4:02 pm
Location: San Francisco, CA

by sethjs

jekyll man wrote:
Mon Apr 09, 2018 10:16 am
How did you measure speed/distance for accuracy?
GPS or speed sensor?
I didn't measure speed directly. I kept power constant. Both bikes have an SRM power meter. Distance was measured by just going around the same track, and also GPS.

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