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Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test
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The P4 project bike is finally mostly complete. Really happy with how it turned out. Still some prep work to do to normalize both bikes to each other but really looking forward to knowing once and for all how good the P4 really was. I'm hoping to test this month at the A2 wind tunnel in NC. I'm open to any criticism or questions or requests.

Primary questions to answer in the tunnel:

1. What is the rider off and rider on CdA for a baseline P4
2. What is the rider off and rider on CdA for a baseline P5
3. What are the best hydration and storage options for the P5
a. BTA vs. modified Torhans Aero 30
b. Modified Specialized Fuel Cell vs. Yann's Bike Xcessories draft box vs. both
c. BTS vertical, BTS horizontal, double BTS ala Sebbie Keinle, double BTS Fizik Mistica mount

Secondary questions to answer:

1. What is the effect of a Zipp NSW 808 vs. HED GT3 on the P4?
2. What is the best helmet for my position given any new helmets at the tunnel?
3. What is the best skinsuit for my position given latest suits on the market?

To do:

1. Modify P4 bottle to fit Vittoria Pit Stop
2. Switch P4 extensions to USE Tula 50 degree to allow BTA bottle to fit
3. Swap cranks and front wheel on P4 for baseline test
4. Bar tape for the P4
5. Prep BTS options for quick changes using spare P5 seatpost and Mistica Saddle
6. Figure out a solution for the SRAM eTap blip boxes for the baseline test.
a. remove the blip boxes and hide the cables inside the Aduro bar
b. leave the blip boxes as is and run a BTA bottle as baseline
7. Procure a really good textured skin suit or two to test.

Discussion:

1. I don't expect the rider-off CdA to be the greatest due to the eTap situation as well as the 20* angled pads, big-ass ski bends, and potentially a BTA bottle with a Garmin 510 sticking off.
2. The rear discs will be different for the test. P5 will run a Super 9, but the P4 will run a Zipp 900 tubular because the Super 9 is barely rideable in the P4 frame given the rear brake situation.
3. With the P5 baseline I hope to replicate my .22 at the A2 tunnel from a couple of years ago. There will be some differences, mainly better shoes (Giro) and a BTA bottle shielding the eTap blip box. I'm also probably a little lighter.
4. Things that will remain the same from my last test will be helmet, skinsuit, wheels, tires, tire pressure, and frame storage
5. I will test at 0* and 10* of yaw
6. I tried a hundred ways but the only way to get smooth braking on the P4 was to route the cable out through the top of the Aduro cover and down into the frame, "properly". All other options affected the cabling.
7. The fit coordinates are *slightly* off but it works. The P4 is 5mm shorter and 5mm lower than the P5 at pad rear, but by keeping saddle to extension tips constant and bringing elbows up 5mm on pads it evens out.
8. The bentos are not the same, obviously. I picked the ones I liked best for each bike, ie. the one that mated with the stem the best.

Cervelo P5 58cm, Aduro bars w/ modified extra low mount, USE Tula 50* extensions, angled pad spacers from the UK, Quarq 165mm 55-42 cranks, Fizik Mistica 65mm, Profile Design bento, Zipp Super 9 disc and 808 NSW front, Vittoria Corsa Speed 23mm w/ latex tubes, frame storage box, SRAM eTap


Cervelo P4 58cm, Aduro bars w/ Zipp Vuka Wing reach modification hack, USE Tula 40*extensions, angled pad spacers from the UK, TriRig OmegaX brake, SRM 170mm 55-42 cranks, Fizik Mistica 65mm, Torhans bento, Zipp 900 tubular disc and HED GT3 tubular front, Vittoria Corsa Speed 23mm tubular tires, P4 bottle for storage, SRAM eTap


Eric Reid
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Chapel Hill, NC
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Last edited by: ericMPro: Feb 10, 19 8:21
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Pics aren't showing
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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why does it matter? both bikes are like multiple generations old at this point.

I'm racing 2019 IM Arizona as part of Team Smile Train. Will I implode? Will I finish strong? Donate to find out more!
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [jkhayc] [ In reply to ]
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jkhayc wrote:
why does it matter? both bikes are like multiple generations old at this point.

And yet the P5 is probably still the fastest if not one of the fastest bikes you can get...
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Can’t wait

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2019: IMTX, Rookie, 70.3 Worlds, Lifetime Oly
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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i think you would have more 3 testing options more

-the rear break adapter for p4 and tririg or magura break.

-and it would be interesting to test one or two other discs renn 555 clincher 24 mm wide and the old zipp 900 clincher for instance.
i guess renn disc would have very little impact on cda but would allow wider tyres ie less rolling resistane and more tyre options . and an alu braking surface is alwyays good with p4 .

- go one chainring and take of front derailleur and ring off on both bikes ( maybe for the bike you think you will go with. Complicated somehow but if you had someone with you at tunnel possibe

http://www.pb3coaching.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:
Pics aren't showing

Here you go!





My YouTubes

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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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For me that GT3 makes any bike look better than it has any right to. Seeing your P4 setup with it makes me mildly regret the move to the Spec disc and full clincher setup instead of going GT3 to pair with my stinger.....would have been cheaper! lol

Yeah, the blip box had me scratching my head when I saw your IG and FB posts. Also, what's up with the shifters? Zipp R2C? Are they there for a more comfortable grip?

0º and 10º? Any particular reason other than to mirror your last test? FWIW, I settled on 0º, 2.5º, and 5º.

Oh, what tire on the GT3?

My YouTubes

Last edited by: LAI: Feb 17, 19 7:37
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [LAI] [ In reply to ]
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LAI wrote:
For me that GT3 makes any bike look better than it has any right to. Seeing your P4 setup with it makes me mildly regret the move to the Spec disc and full clincher setup instead of going GT3 to pair with my stinger.....would have been cheaper! lol

Yeah, the blip box had me scorching my head when I saw your IG and FB posts. Also, what's up with the shifters? Zipp R2C? Are they there for a more comfortable grip?

0º and 10º? Any particular reason other than to mirror your last test? FWIW, I settled on 0º, 2.5º, and 5º.

Oh, what tire on the GT3?

Yeah I really like the P4 and the GT3. Great combination. It's a 23mm Vittoria Corsa Speed on both the disc and the GT3.

The shifters are R2C, put on backwards so that there's a fair bit of shifter that juts out to the side of the extension. It's perfect for digging the heel of your hand into for a really locked in position.

No reason on yaw angles, but I've read that the GT3 is not so good at high yaw angles so I wanted to confirm that. For the apples to apples test, I wanted to compare to my old test so hence the 0 and 10.

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Fishbum] [ In reply to ]
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weird they show up for me... Google Chrome.

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [pk] [ In reply to ]
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pk wrote:
i think you would have more 3 testing options more

-the rear break adapter for p4 and tririg or magura break.

-and it would be interesting to test one or two other discs renn 555 clincher 24 mm wide and the old zipp 900 clincher for instance.
i guess renn disc would have very little impact on cda but would allow wider tyres ie less rolling resistane and more tyre options . and an alu braking surface is alwyays good with p4 .

- go one chainring and take of front derailleur and ring off on both bikes ( maybe for the bike you think you will go with. Complicated somehow but if you had someone with you at tunnel possibe

I really like the look of the new SRAM group set and integrated power meter so a 1x w/ 165mm cranks with a 50t front and 10-32 rear would be very interesting on the P4.

You make a good point about the rear brake adapter test, but I don't think I'm willing to go through that trouble.

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [jkhayc] [ In reply to ]
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jkhayc wrote:
why does it matter? both bikes are like multiple generations old at this point.

It doesn’t matter. Mostly just to satisfy my own curiosity and have a capstone moment for my P4 build.

OTOH, if I get good data, and if Kiley’s data is good, then maybe we can extrapolate to the P5D if someone else tests that one.

Finally on the hydration and storage, I was thinking maybe that information might benefit others with P5s

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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I'm just giving you a hard time.

Besides, we all know the P5x is the fastest bike currently available.

I'm racing 2019 IM Arizona as part of Team Smile Train. Will I implode? Will I finish strong? Donate to find out more!
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [LAI] [ In reply to ]
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LAI wrote:




Is that the modified fuel cell?
Last edited by: BigBoyND: Feb 9, 19 5:14
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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Same comment as I left on your Insta, this P4 is just begging for a 1x setup. Very curious to see the results.

ZONE3 - We Last Longer
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [BigBoyND] [ In reply to ]
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BigBoyND wrote:
LAI wrote:




Is that the modified fuel cell?

yes. the rubber top part blew off on the way home from a race one day :(

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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looks good, should be a fun test! More data is always worth it!

*Man... I love the reach. I miss that.

My Blog - http://leegoocrap.blogspot.com
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [ericMPro] [ In reply to ]
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How do you do the P4 bottle pit stop mod?

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David Gramer
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [DGTri] [ In reply to ]
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I did it once before on my old P4... you take an exacto blade and cut the nozzle off in a circle and then slide the Pit Stop in horizontally. A little bit of time under a hair dryer helps soften the plastic to fit the Pit Stop better.

Then, you create a trap door on the bottom of the bottle for the rest of the flat kit



DGTri wrote:
How do you do the P4 bottle pit stop mod?

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [tessar] [ In reply to ]
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tessar wrote:
Same comment as I left on your Insta, this P4 is just begging for a 1x setup. Very curious to see the results.

I have to agree with this. I am guessing the P4 with equivalent setups would be a faster low yaw bike. Strip all the worthless front derailleur garbage and go super clean with a 58 for a fast flat TT bike and use the P5 when you have to do some climbing or anticipate slower speeds and higher yaw angles.

If you follow the recent Rotational drag thread, there are some good tips from Josh Portner on trispokes in general. Unfortunately, you will probably be disappointed by the GT3, but it would be cool to see if it tests faster when mounted backwards! Also remember that the wind tunnel testing isn’t going to be definitive in the watts to spin department. Need some track testing for that.
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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:
I did it once before on my old P4... you take an exacto blade and cut the nozzle off in a circle and then slide the Pit Stop in horizontally. A little bit of time under a hair dryer helps soften the plastic to fit the Pit Stop better.

Then, you create a trap door on the bottom of the bottle for the rest of the flat kit



DGTri wrote:
How do you do the P4 bottle pit stop mod?




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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [trail] [ In reply to ]
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yeah what can I say, that was a long time ago!

Eric

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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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:

yes. the rubber top part blew off on the way home from a race one day :(

That looks nice! Does it line up well with the downtube and seat tube widths?
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [BigBoyND] [ In reply to ]
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I got creative with a dremmel but yes. Yann’s will be better though, assuming they fit a pit stop

BigBoyND wrote:
ericMPro wrote:

yes. the rubber top part blew off on the way home from a race one day :(

That looks nice! Does it line up well with the downtube and seat tube widths?

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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Re: Cervelo P4 vs. Cervelo P5: The Definitive Wind Tunnel Test [Morelock] [ In reply to ]
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yeah even on the P4 I still need more reach, because the P5 has the extra low mount which is awesomely long and low.

I get more reach with the diagonal Zipp Vuka Wing hack that I do... turns out two of the holes are 2x the distance of a standard set of holes, so you drill a third hole in the middle and then bolt them down to the ADuro. Adds 25mm of reach.


Morelock wrote:
looks good, should be a fun test! More data is always worth it!

*Man... I love the reach. I miss that.

Eric Reid
AeroFit | Instagram Portfolio
Chapel Hill, NC
Aerodynamic Optimized Bike Fitting, Retul Pre-Purchase Bike Fitting, USAT Level 1 Triathlon Coaching, Nutrition
Ask me: Scody Optimized Speed Suits | CeramicSpeed Oversized Pulley Systems | HUUB Skinsuits and Wetsuits | Ventum Bicycles and Frames
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