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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [turdburgler] [ In reply to ]
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turdburgler wrote:
At any rate that P4 is nasty.

Yes!!! Amazing bike.

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Absolutely love that frame. FYI I tested at A2 when I lived in the states. I think your results are likely legit. There is too much coming from Boardman that makes me question the results. There was a pro triathlete around .185. My results I know are not right and were too low. A bunch of other testers with super low results that don't reflect TTs when considering their power input. I'm curious how/why different tunnels tests that differently because I think A2 is accurate.

You planning to race on the P4 this year? Also my fiancee would like some feedback (not from me) on her position. Do you have a link to purchase an online fit session/consultation?
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [turdburgler] [ In reply to ]
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shoot me a DM and we can discuss there.

Yes, definitely planning to race the P4, I guess it will be my "low yaw" bike LOL.

I made a mistake... I should have tested my old position first to "calibrate" the tunnel against my 2016 data, but it would have required removing a spacer and changing a fork on the P5 which is basically impossible or very time consuming at the very least. Also, my shoes from two years ago are so old and dusty in the garage it wasn't ideal.

That said, I wasn't out to compare myself to my old self, I was there to optimize storage and hydration and helmets, which I did. I know I'm reasonably aero, my results are OK. What I didn't expect was the surprising data and the insight it's given me.

E

turdburgler wrote:
Absolutely love that frame. FYI I tested at A2 when I lived in the states. I think your results are likely legit. There is too much coming from Boardman that makes me question the results. There was a pro triathlete around .185. My results I know are not right and were too low. A bunch of other testers with super low results that don't reflect TTs when considering their power input. I'm curious how/why different tunnels tests that differently because I think A2 is accurate.

You planning to race on the P4 this year? Also my fiancee would like some feedback (not from me) on her position. Do you have a link to purchase an online fit session/consultation?

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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ericMPro wrote:
What I didn't expect was the surprising data and the insight it's given me

this statement is surprising and yet, not. You are about as educated and vocal about aeroness as anyone on here and yet you go to the tunnel and come out “surprised” by the results. Curious what the data says but That probably tells the rest of us how much of a crap shoot this all is without personal testing.
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [DFW_Tri] [ In reply to ]
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Fastest run of the day... .226 at 0 and .209 at 10.



Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Is that Torhans Bento X?
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [DFW_Tri] [ In reply to ]
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yes. It most closely matched the profile of the back of the Alpha One.

DFW_Tri wrote:
Is that Torhans Bento X?

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Love the P4! Looking forward to racing my own project this year. It's hard to tell, but how did you manage to route your rear brake cable without an exposed loop of housing over the stem?
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [wthecoyote] [ In reply to ]
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I had it that way when I was using the Aduro bars, but with the TriRig Alpha One it was not necessary.

wthecoyote wrote:
Love the P4! Looking forward to racing my own project this year. It's hard to tell, but how did you manage to route your rear brake cable without an exposed loop of housing over the stem?

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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ericMPro wrote:
trying to see if there's any differences here...


here are the difference I saw on a quick glance:
hands lower
back high on p4
head position is slightly different

Most of all the above is bc you're entire body is shifted forward a bit, probably/maybe 20mm

Brian Stover USAT LII
Accelerate3 Coaching
Insta

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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [desert dude] [ In reply to ]
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The higher Ness is because the P4 BB is higher. I took that into account

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Just a gut feeling, but I think if you had more stack in the front end (reduced your saddle to pad drop) your cda would drop.

Cool comparison, thanks for sharing.

My Blog - http://leegoocrap.blogspot.com
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Morelock] [ In reply to ]
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Morelock wrote:
Just a gut feeling, but I think if you had more stack in the front end (reduced your saddle to pad drop) your cda would drop.

Cool comparison, thanks for sharing.

Could you explain why? As I go further down this rabbit hole Im finding so many nuances.
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Morelock] [ In reply to ]
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Nope tried that. I’m actually pretty consistent at all stacks.

That’s the beauty of the Alpha One. When I got as low of a CdA as I have now I had to have two sets of Aduro bars and extensions and have the brake cable disconnected and all that and then wrench all that crap and OMG. This time around it was a 5 second job.

At any rate, reach makes me faster, not stack. Except low stack I sail better at yaw. Also, high hands.

.
Morelock wrote:
Just a gut feeling, but I think if you had more stack in the front end (reduced your saddle to pad drop) your cda would drop.

Cool comparison, thanks for sharing.

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
Quote Reply
Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Fishbum] [ In reply to ]
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Fishbum wrote:
Morelock wrote:
Just a gut feeling, but I think if you had more stack in the front end (reduced your saddle to pad drop) your cda would drop.

Cool comparison, thanks for sharing.


Could you explain why? As I go further down this rabbit hole Im finding so many nuances.

For me, it's about getting things compact. I think big drop can work, and I think lots of reach can also work. I think the "line" is hard to find and easy to cross because up to a point it both starts looking better and often just is better period, so the next logical step is more=more, but of course that's not the case always. When there are two big cylinders (your upper arms) sticking out by themselves, the eyeball wind tunnel starts throwing off warning bells *to me.*

In my experience, getting really slippery is about 1.) getting your head out of the way and 2.) having as few distinct "shapes" as possible.

It's not a guarantee, and as Eric said above he's tested other stuff and this is what works. He's also a pretty tall looking guy, something I've never had to worry about. ;) That said, I would be very, very surprised if .23x cda was a hard stop for any triathlete.

What you really want out of aero testing positions is context. Think of it this way.
Is lower or higher faster? Longer or shorter?
Yes.

My Blog - http://leegoocrap.blogspot.com
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Fishbum] [ In reply to ]
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Fishbum wrote:
[ As I go further down this rabbit hole Im finding so many nuances.

When it comes to aero testing it's all about nuances. There is no universal "thing" that is going to work all the time once you've started to optimize yourself.

Brian Stover USAT LII
Accelerate3 Coaching
Insta

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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [turdburgler] [ In reply to ]
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turdburgler wrote:
Absolutely love that frame. FYI I tested at A2 when I lived in the states. I think your results are likely legit. There is too much coming from Boardman that makes me question the results. There was a pro triathlete around .185. My results I know are not right and were too low. A bunch of other testers with super low results that don't reflect TTs when considering their power input. I'm curious how/why different tunnels tests that differently because I think A2 is accurate.

Talking to some of the guys who test a lot in the Boardman tunnel, they're finding that that tunnel reads low compared to their on track testing. One of the big differences between A2 and Boardman, is that A2's numbers all include the drag from the struts. So in reality your on road numbers are going to be, perhaps, a bit lower than the tunnel numbers. The guess is that when Boardman Tunnel is pulling the struts out of the overall number they are overcompensating.



Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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ericMPro wrote:
Nope tried that. I’m actually pretty consistent at all stacks.

That’s the beauty of the Alpha One. When I got as low of a CdA as I have now I had to have two sets of Aduro bars and extensions and have the brake cable disconnected and all that and then wrench all that crap and OMG. This time around it was a 5 second job.

At any rate, reach makes me faster, not stack. Except low stack I sail better at yaw. Also, high hands.

.
Morelock wrote:
Just a gut feeling, but I think if you had more stack in the front end (reduced your saddle to pad drop) your cda would drop.

Cool comparison, thanks for sharing.

I thought coming up on the front might be better as well. I would be interested to figure out if the high point at your back, which is above the top of the helmet, is causing the air to separate and creating a low pressure area behind your butt. A skin suit with a rougher back, like the Castilli would be interesting. Bringing the seat back and down a bit might also help.
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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ericMPro wrote:
Fastest run of the day... .226 at 0 and .209 at 10.


That's all well and good until you actually have to look to where you're going.



Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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How tall are you? Your position looks slippery as wet ice but your cda seems high.
For reference my ching'ed cda is 0.21 but I don't look as good.
I'm 5'11" with short legs and a long back on a P4
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Ex-cyclist] [ In reply to ]
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Yeah I did 22 runs with three yaw angles each so I selected a crossbar on the front of the tunnel screen to stare at in order to keep the data consistent.

That said, the crossbar is what, 8m out in front at a height of 1m or so... giving me probably 15m of visibility? In certain situations that’s enough.

Also, with my morphology I can easily come up... Alpha One was helpful for changes here... high stack only hurts me at yaw. However shrugging and turtling is a big hit... 5min over 180km for me.

Ex-cyclist wrote:
ericMPro wrote:
Fastest run of the day... .226 at 0 and .209 at 10.


That's all well and good until you actually have to look to where you're going.

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [bluntandy] [ In reply to ]
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I’m 6’2” and 175. My old .22 position at A2 had my saddle further back effectively giving me more reach, with 10mm lower stack. I moved it forward based on this winters training, and also I’m getting old.

I’m ok with the .235 with all my luggage aboard... my results are ok so far since the 2016 changes I made.

E

bluntandy wrote:
How tall are you? Your position looks slippery as wet ice but your cda seems high.
For reference my ching'ed cda is 0.21 but I don't look as good.
I'm 5'11" with short legs and a long back on a P4

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Ex-cyclist] [ In reply to ]
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Why does this even need to be said? Obviously one would think Eric is experienced enough to either hold a higher position while racing or peak enough that upstream vision would not be an issue. As he said above he's in the tunnel trying to get repeatable data that he can use to make informed decisions on what position and what equipment to race. It's not like he is posting a critique my fit trainer video.

FWIW, I wish I would have had time to test with my head lower like Eric did, as I normally race in a similar position. My "peaking" to low head ratio is probably 40:60.


Ex-cyclist wrote:
ericMPro wrote:
Fastest run of the day... .226 at 0 and .209 at 10.



That's all well and good until you actually have to look to where you're going.

My YouTubes

Last edited by: LAI: Apr 8, 19 6:43
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [LAI] [ In reply to ]
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I’ve never understood why people think you need to see a mile up the road in a race. I guess if all you’re doing is Ironmans it may be that busy but I’ve never feel like I’m looking that far ahead racing.
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Now I'm not good at fitting at all but it seems to me that the angle of your arms to your head is different in the pictures. On the P5 the angle/gap between your arms and head is closer/smaller. Your arms look "separated" from your aero bars on your P5 and they look more "connected" on our P4. I don't have a clue if that matters or not....just an observation.
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