Getting a low CdA on an aero road bike with clipons

Sep 28, 19 14:37

Post #1 of 21 (5061 views)

I know it's always a hot topic here and thought I'd share some of the data from a recent video we've done. We used me as the test rider in the wind tunnel recently and on a BMC Timemachine TMR01 (the older one, not the new one with the integrated bottles) we managed to get my CdA from 0.2934m^2 (bibs, jersey, road helmet, deep section wheels in the drops) down to 0.2093m^2 (skinsuit, aero helmet, clip on aerobars, disc and deeper front).

VIDEO HERE

It was better than I expected given we literally just chucked the clipons on the bike with no adjustments to stack height or saddle position (although we did make two small adjustments to pad width and extension reach), shows that you can definitely get away with a road bike for triathlon if you've just got the one bike.

If we do a breakdown of the savings it was

Position 68% (clipons)
Clothing 21% (skinsuit/overshoes)
Wheels 7.5% (double deep sections - ZEPHYRs vs deeper section and disc - TITAN/Disc)
Helmet 3.5% (Aerohead)

The Aerohead isn't a great helmet on me (we already knew that) but we used it because it's popular and works alright on a few people. A better helmet (I currently use a Catlike Crono) would save a bit more. The Aerohead was 3.6w faster than a Specialized Evade at 45kph.

My TT bike CdA (outdoors) is ~0.185m^2, sometimes a bit lower depending on how well I hold my position - but that's on a P4 with all the trimmings (single ring etc.). I wouldn't be surprised if getting a <0.200m^2 would be achievable on that BMC.

AeroCoach UK
http://www.aero-coach.co.uk

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 28, 19 16:05

Post #2 of 21 (4994 views)

One of the YouTube channels (Maybe GCN) did a power test with clipons.
To all intents there was no difference.

Which means in a Sprint Tri you might come out ahead wearing running shoes, minuscule loss of speed, quite a few seconds in T1 and T2.
Some running shoes, like Hoka have soles that won't bend much (so no arch problems).

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 28, 19 16:27

Post #3 of 21 (4979 views)

Very interesting

What skin suit please?

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 28, 19 16:36

Post #4 of 21 (4970 views)

thanks for sharing

this was a similar video i saw last month:

https://www.youtube.com/watch?v=7lK1xC0Z5FA

I watch these as I'm tight on budget and have had good results on my road bike w/bars and think i'll stick with it for another couple years.

Re: Getting a low CdA on an aero road bike with clipons [michael Hatch] [ In reply to ]

Sep 28, 19 19:21

Post #5 of 21 (4898 views)

michael Hatch wrote:

One of the YouTube channels (Maybe GCN) did a power test with clipons.
To all intents there was no difference.

Which means in a Sprint Tri you might come out ahead wearing running shoes, minuscule loss of speed, quite a few seconds in T1 and T2.
Some running shoes, like Hoka have soles that won't bend much (so no arch problems).

As a (former?) aero nerd, I can confirm the validity of this strategy. I use these and my Altras with speed laces: https://pedalinginnovations.com Surprisingly enough, IIRC this shoe/pedal combo is only be 2-3 watts slower than my very slick Simmons cycling shoes. If I go high and say I lose 5 watts, on a sprint bike I only lose 10 seconds to aero. In the three or four races I've run that pedal/shoe combo I pick up at least that much time in T2. Last time I raced Fort Desoto, a guy that was right behind me on the bike commented after the race "I was right on your tail for whole bike but you just disappeared in T2." I suspect I pick up a bit of time in T1, the mount, and the dismount as well (no need to fiddle with straps).

Between my sprint tri results, some field testing, and some mock transition testing, I think this pedal shoe strategy is worth about 20 seconds net. In a sprint tri that's a lot.

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 28, 19 19:22

Post #6 of 21 (4893 views)

Pretty nifty result, thanks for sharing. Makes me wonder how fast someone could get on an "aero" gravel bike like a 3T Exploro.

Edit: holy cow I just realized that result was with the drop bar still in place. That's worth a good chunk of drag on its own!

Last edited by: GreenPlease: Sep 28, 19 19:24

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 28, 19 21:29

Post #7 of 21 (4825 views)

To contribute to topic, I can do 42kp/h avg. for an hour @220Watts. That's with a Giant TCR climbing road bike,30mm rims, clip-ons, skinsuit, standart road helmet, no overshoes, @700m altitude. What do you think about my CdA?

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 29, 19 0:04

Post #8 of 21 (4746 views)

It's a NoPinz skin suit. Made in the UK and a partner of AeroCoach.

http://www.tri-monkey.co.uk

Re: Getting a low CdA on an aero road bike with clipons [michael Hatch] [ In reply to ]

Sep 29, 19 0:32

Post #9 of 21 (4731 views)

michael Hatch wrote:

One of the YouTube channels (Maybe GCN) did a power test with clipons.
To all intents there was no difference.

Which means in a Sprint Tri you might come out ahead wearing running shoes, minuscule loss of speed, quite a few seconds in T1 and T2.
Some running shoes, like Hoka have soles that won't bend much (so no arch problems).

Ah this was clip on aerobars - not clips and straps for your shoes

AeroCoach UK
http://www.aero-coach.co.uk

Re: Getting a low CdA on an aero road bike with clipons [GreenPlease] [ In reply to ]

Sep 29, 19 0:35

Post #10 of 21 (4727 views)

GreenPlease wrote:

Pretty nifty result, thanks for sharing. Makes me wonder how fast someone could get on an "aero" gravel bike like a 3T Exploro.

Edit: holy cow I just realized that result was with the drop bar still in place. That's worth a good chunk of drag on its own!

From some testing I did absolutely ages ago it was 7w at 45kph for drops and STI levers vs aero base bar, but I think that was with a few cables exposed (in the video the shifters are eTap).

Next fun video is a bikepacking one actually - but yes I’d be interested in a 3T Exploro gravel aero setup. We have a local guy with one so might ask him!

AeroCoach UK
http://www.aero-coach.co.uk

Re: Getting a low CdA on an aero road bike with clipons [robius] [ In reply to ]

Sep 29, 19 0:36

Post #11 of 21 (4723 views)

robius wrote:

To contribute to topic, I can do 42kp/h avg. for an hour @220Watts. That's with a Giant TCR climbing road bike,30mm rims, clip-ons, skinsuit, standart road helmet, no overshoes, @700m altitude. What do you think about my CdA?

Sounds quick :) aero helmet would be the next upgrade from a value for money perspective

AeroCoach UK
http://www.aero-coach.co.uk

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 29, 19 3:58

Post #12 of 21 (4649 views)

Interesting video, thanks

I noticed you use an aero bottle (the Elite apparently)

For LD tri (70.3 and above), more bottles are needed, and installing them between the arms and behind saddle, as you pointed out in another interesting review (thanks for that also) will indeed give you excellent results, same as on a "real" TT/Tri bike.

https://www.aero-coach.co.uk/water-bottle-testing

With the possibility to install clipons with wireless buttons (e-tap, ...), I m really wondering if, going to disk brakes, instead of buying two bikes (one road + one TT), I will instead buy only one very aero road bike.

With a good clipon + wireless shifters + race wheels + my usuals behind saddles bottle + aero pouch and between arms bottle (and of course no round bottle hanging in the flow), performance of the bike will be very very near to a real tri bike.

Re: Getting a low CdA on an aero road bike with clipons [Pyrenean Wolf] [ In reply to ]

Sep 29, 19 4:44

Post #13 of 21 (4622 views)

Pyrenean Wolf wrote:

Interesting video, thanks

I noticed you use an aero bottle (the Elite apparently)

For LD tri (70.3 and above), more bottles are needed, and installing them between the arms and behind saddle, as you pointed out in another interesting review (thanks for that also) will indeed give you excellent results, same as on a "real" TT/Tri bike.

https://www.aero-coach.co.uk/water-bottle-testing

With the possibility to install clipons with wireless buttons (e-tap, ...), I m really wondering if, going to disk brakes, instead of buying two bikes (one road + one TT), I will instead buy only one very aero road bike.

With a good clipon + wireless shifters + race wheels + my usuals behind saddles bottle + aero pouch and between arms bottle (and of course no round bottle hanging in the flow), performance of the bike will be very very near to a real tri bike.

I actually did a 6hr road race recently (Revolve 24 - basically a massive crit around a motor circuit) and didn't stop for nutrition, and there was no provision for handups. When we were in the tunnel I also put two Elite Crono bottles in the frame and a top tube box and managed to get a CdA of 0.2443m^2 in a breakaway road position with bibs and jersey (I had a skinsuit during the 6hr race), which was decent enough - if you need round bottles though I would definitely suggest hiding them behind you or between your arms. You can always put an aero bottle in the frame triangle filled with gels which is a nice way of having a few extra calories.

AeroCoach UK
http://www.aero-coach.co.uk

Re: Getting a low CdA on an aero road bike with clipons [robius] [ In reply to ]

Sep 29, 19 5:58

Post #14 of 21 (4586 views)

robius wrote:

To contribute to topic, I can do 42kp/h avg. for an hour @220Watts. That's with a Giant TCR climbing road bike,30mm rims, clip-ons, skinsuit, standart road helmet, no overshoes, @700m altitude. What do you think about my CdA?

CdA is only one variable amongs a pool of other variables. To estimate CdA, you really should rely more on simply watts and speed.

42kph is fairly for a TT (better than most, but worse than many).
220 watts is likely below average for a male who can ride at that speed. You're either much smaller/lighter than average, on a course with some elevation drop, in a group ride, tailwind,... or don't have a properly calibrated power meter. ...All are possible. In conclusion, I think your CdA could range from insanely good to mundanely average.

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 29, 19 11:30

Post #15 of 21 (4481 views)

https://www.youtube.com/watch?v=OjYoNL4g5Vg

:0)

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 29, 19 13:35

Post #16 of 21 (4413 views)

Xavier wrote:

robius wrote:

To contribute to topic, I can do 42kp/h avg. for an hour @220Watts. That's with a Giant TCR climbing road bike,30mm rims, clip-ons, skinsuit, standart road helmet, no overshoes, @700m altitude. What do you think about my CdA?

Sounds quick :) aero helmet would be the next upgrade from a value for money perspective

Sounds borderline impossible to me, lol.

Except maybe downhill.

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 29, 19 13:54

Post #17 of 21 (4390 views)

Can you please let use know about your front end set-up? What aero drops and what aero bars you used?

Re: Getting a low CdA on an aero road bike with clipons [BMANX] [ In reply to ]

Sep 29, 19 14:41

Post #18 of 21 (4352 views)

BMANX wrote:

Can you please let use know about your front end set-up? What aero drops and what aero bars you used?

Sure - on that bike I’ve got Bontrager Elite Aero VR-CF bars (aluminium) in 38cm as they have a tiny bit more reach and come in narrow sizes with internal cable routing. 130mm stem too. The clipons we used were Zipp Vuka Clip with the below bar mount, and our Angles extensions (35deg) and Align Wing arm rests

AeroCoach UK
http://www.aero-coach.co.uk

Re: Getting a low CdA on an aero road bike with clipons [Xavier] [ In reply to ]

Sep 29, 19 14:57

Post #19 of 21 (4337 views)

Thank you

Re: Getting a low CdA on an aero road bike with clipons [Mario S] [ In reply to ]

Sep 29, 19 17:33

Post #20 of 21 (4278 views)

Mario S wrote:

Xavier wrote:

robius wrote:

To contribute to topic, I can do 42kp/h avg. for an hour @220Watts. That's with a Giant TCR climbing road bike,30mm rims, clip-ons, skinsuit, standart road helmet, no overshoes, @700m altitude. What do you think about my CdA?

Sounds quick :) aero helmet would be the next upgrade from a value for money perspective

Sounds borderline impossible to me, lol.

Except maybe downhill.

Air pressure is about 92% of sea level air pressure, so that helps.

But without information re: topography, lots variables.

If it were flat, I'd hesitate to trust the power meter, as it'd suggest a sub 0.2 CdA...

Re: Getting a low CdA on an aero road bike with clipons [echappist] [ In reply to ]

Sep 30, 19 2:04

Post #21 of 21 (4160 views)

With air pressure adapted for 700m and some standard rolling/friction setting, I find 0,17 CdA.

Either you are small and lightweight (Castroviero effect), either you have superslick aero (Huub Wattbike Team effect), either there is a problem with data (power or speed - need some calibration effect).

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