Saddle will be 5cm behind BB
Extensions at 80cm in front of BB

Also, I want to make sure the seatpost length is good.

Thanks!

Looks like you'll be a maxed out on reach 56cm bike. If you were doing triathlon I'd say get a 58cm but since you're UCI restricted that extra reach would be wasted.

Even with a reach of 490mm you'll be limited to 310mm extensions, so you might even be able to make the argument for a 54cm P5d. You'd have to move pad reach back to ~ 456-470mm to make that work. I'd go with a 56cm.

Make sense?

Eric

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This is great! - thanks for the info.

For my understanding: on the P-Series 56cm, the frame reach is: 425mm. The Metron TFA gives a pad range of -14 to + 76mm.
Thus, the max reach I could get on the P-Series 56cm would be 501mm, correct?

Do you have any comment on orienting the basebar at +/- 25mm? For me, I'd orient it at +25mm, just for general comfort when riding in traffic (I live in a city and need to ride to-from the TT practice areas).

thanks also for the comment on the P5d, though unfortunately, the price is too high for me.

Frame reach plus stem reach plus/minus TFA mount -14/+76 equals your pad reach.

However, I'm seeing -9mm to -99mm as the range on the Vision website. I'm not sure how long the stem is.

For example, 425mm + 90mm (-17 stem) = 515mm. 515mm - 9mm = 506mm max reach.

I'd do +25.

Make sense?

E

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Thanks so much for the expert opinion Eric, much appreciated!

Hi Eric,
Appreciate your support around slowtwitch. I’m curious about the p5 disc. I have attached a retul fit (this was for a medium/54 trek speed concept) but with 2 caveats - I found the fit too low on my medium speed concept so swapped out the monoriser to a 25mm from the 15mm one. So stack will be increased 10mm. Also the reach is very short 419? That doesn’t sound right as a run a mono plug in fully maxed out on a medium far stem. I feel as though I ride with much more reach than that 419? I’m not sure but I ride a medium speed concept with medium far stem and the 25mm riser as mentioned, I’m not sure if that helps I have the mono bars pretty much maxed out all the way out so I actually thought my reach is quite long. I’m any event is it safe to say I can replicate said position on a medium p5? If it makes a diff I’m 178/179cms.
I’d see the bikes in person but they are all a case of buy and order them in and wait. I can mess around with fit once here as I understand the ex10 allows a massive fit range, just wanted to double check a 54 is the go:
As an aside do you or anyone know what crank size comes stock with a 54? I have a stages 170mm crank and wondering if that’s something I’m going to be able to use or not
Thanks 🙏

With a stack of 629mm and a reach of 413mm you are right, something is off. Way too high for an 48cm P5d at that reach or way too short for a 56cm P5d at that stack.

Can you do a quick reach measurement on your bike for me?

Eric

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Hey Eric,

Looking at a PX.

Stack: 650 can go down to 635 if I been riding TT enough; Reach: 455 (back edge of pad)
6'2" 34inseam

Cervelo P2: I road a 58
Cervelo P5-6: 56cm

I use extenders on my shoes for mid-cleat position (47 shoe). I have gone to 165's for cranks, but shoe/tire overlap can be an issue.

It looks like I good go either Large or XL. The front center of 614 on the Large seems tight?

What do you think? Trade-offs?

Cheers, Keith

Hi Keith, thanks for reaching out.

At a pad stack of 635mm and reach of 455mm you could actually “fit” on all four sizes of PX.

At 650mm, it would be M, L, or XL with your coordinates in the middle of the range on the size L. Any chance of getting longer?

At 635mm, you’d be basically slammed on a size XL, but would have longer front center, and at 30mm difference it might be decisive.

A trade off might be that your configuration *might* be a little faster on size L instead of XL.

Make sense?

Eric

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Thanks Eric, yes it makes perfect sense and we are on the same page. I am actually leaning towards XL to avoid the toe overlap and to your point the L "might" be a bit faster; perhaps the slammed position versus spacers will be a wash aero wise?

I used to be a fair bit longer with no tilt on bars, but with angled bars it has shorten up as a product of comfort. I do ride a fairly steep position as well (nose of Cobb max ~30mm forward) which also might be for a better ride on XL (too far forward on L)?

I guess they wanted to cut down on the molds for this bike as it certainly is not apples to apples with their other builds.

Thanks again!

I currently ride a 58cm P2 quite comfortably, though I was professionally fit and had to replace original stem and play with configuration. I am competing at IM distance, and want to get a bit lower. I’m quite flexible though have a long neck. I am 6’3.5” and proportional upper / bottom.

My 2018 numbers from a professional fit follow and I have since changed slightly just to get a little lower / more aero on the bars.

Arm pad stack: 709mm (about 703mm now)
Arm pad reach to back of pad: 434mm
Arm pad width: 212mm

I would very sincerely appreciate your opinion. While I am looking Cervelo P-series (assume 58cm), I am really asking for help re: P3X and whether I would be XL or could fit the large as I have my eye on one for sale now.

DC -

Hey, I just got fit and looking at a 56cm Cervelo PSeries 105. I see on the website it looks like I will fit on a P5 either a 56 or 58 but the geometry and cockpit adjustments are different I assume. Will I fit on a Cervelo P Series?

Reach: 451mm
Stack: 680mm
Width: 325mm

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Hi, thanks for reaching out.

At that stack and reach, you're sort of tall for a 56cm and sort of narrow for a 58cm. The P-Series is *very* adjustable, so a 56cm will work for you, but I'm only noting your fit coordinates because I think you're slightly unorthodox and might be evolving in the future.

Make sense?

Eric

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Yes, thank you!

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My Strava | My Instagram | Summerville, SC | 35-39 AG | 4:41 (70.3), 10:05 (140.6) | 3x70.3, 1x140.6 | Cat 2 Cyclist

Thanks for your help. I am looking at a P-series.

Pad X = 69cm
Pad Y = 46cm
Pad Z = 26cm
Saddle to armrest (if this helps) = 51cm

Here goes...

To start, my left humerus is 50mm shorter and so the P-series is where I'll have to look. No mono riser for me!

Pad X: 500
Pad Y: 585 right/635 left
Pad Width: 290

From discussions with the fitter...I'm long-torso'd and getting reach on a smaller frame is a challenge. Any chance a Cervelo will fit me?

Hi, thanks for reaching out.

You are most definitely a 58cm P-Series :)

Eric

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Fascinating.

I would have thought your pad delta would be some number between 50mm and 0mm, but not actually 50mm. Like, some non 50 number would equal some component delta of stack and some component delta of *reach* as well.

How are you so long that you’re at 500mm reach but your arms are still perpendicular is what I’m wondering. Like, your humerai are perpendicular to the ground, and thus a 50mm delta.

A slammed 56cm P5 would be at 593mm stack and 510mm reach, so you are close but sort of too long for a 54cm but too low for a 56cm even before we take the humerus into account.

Let’s riff on this more, I’m interested. If it were me I’d optimize for speed (the P5) and for the lower pad and then 3D print a wedge to match.

Make sense?
E

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Eric,

Thanks for the quick response. I've attached a photo from the fit. It looks like I'm perpendicular enough, maybe a degree or two off. I'm on a Gen 2 Speed Concept now with the mono riser and I want to be able to pedestal my bar/pad together. I want to get back to having the same relationship between pads and bars on each side like I had on my old P2 where my hands had the same grip on the extensions where I threw my 50mm pedastal under the clip-ons. Right now, my left pad is raised and even with a Zipp Evo 110, my hand hits the end of the extension and not a great grip. We looked at a few bikes after the fitting and what you've identified my predicament. I either can't get low enough on a larger frame, or can't get enough reach on a smaller frame. And, to be honest, the P5 is just out of my price range. My saddle setback is at 15 if that helps.

Hey Eric,

Following-up on this one, did some measurements based on current P5-6 and I have ~12mm before I get toe contact (it is a 56). Seems to me that if I keep current position/cranks I will clear with the large PX. I am thinking the reach for an XL might be a bit much when out of aero (I like ride a lot of hills) and not much room to go down.

Me math puts me at about 35mm position for arm pads on a large. I had concerns being too far forward on L with the short wheelbase but I think it should be good? Do you concur? I have never really been such a tweener on a bike, but the loss of resolution with the PX with just 4 sizes makes it tricky.

Thanks for this service, it is helpful!

Dumb question but what does it feel like or “do” when you ride on level pads?

Thanks for the response. My *personal* fit philosophy would put your upper arms closer to 45 degrees than to zero/90 degrees as you have them in the pic, which would make you even longer. That said, if you’re going to err, err on the side of the longer frame.

The P-Series will be very adjustable and you will be able to pedestal one side. You’ll have to get creative to get the ski bend tip to match, like a USE Tula on the low side and a regular “depth” ski bend on the high side. You’ll have to play with extension and pipe cutting to get the ends to match up.

Make sense?

E

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I think you have to choose which variable and go from there.

From the perspective of shoes and cleats and safety it’s the XL. The XL also supports optimizing for going fast in aero.

If on the other hand you optimize for or rather against “too big” or “too long” and also “position” which includes aero and non aero, it’s the L.

Have you thought about 155mm cranks? How often does a toe contact a wheel in normal triathlon settings?

E

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Hi Eric,


Happy holidays! What a great thread, thank you for providing this valuable service. Reading the thread has really changed my understanding of tri bike sizing. I'm potentially looking to switch to disc brakes and interested in the P5 disc.


Currently riding a 51 cm P3 (2014), which has worked after changing to a very adjustable cockpit. Measurements:
Stack - Pad Y 605 mm
Reach - Pad X 470 mm
Saddle height 700 mm
Height 1695 mm
Inseam 780 mm
Cranks 165 mm
Aerobar/pads tilt 12*


I've taken a look at all the info, measurement charts etc you and cyclenutnz have provided. Seems I could fit onto a 54 or 56. Hoping to achieve a stable ride with a larger size bike.

I do have a possible 56 P5 disc with the EX10 riser on my sight. The 56 seems against conventional wisdom, like you said in post #918 to another poster with quite similar measurements. I understand I'd be somewhat limited on going much lower on the 56.


What do you think, have a drunk a few too many glasses of wine over xmas to even consider the 56? Any feedback appreciated. Thank you!

Hi, thanks for reaching out. Glad the thread is helping.

With a pad stack of 605mm and a pad reach of 470mm you’re pretty much square in the middle of the range for a 54cm P5d.

I hear you about availability and the 56cm, but the 54cm would be more optimal for both performance and future fit. It also depends on your future fit. With a 54cm you can get 20mm longer or with a 56cm you could only get like 8mm lower. These will be affected by tilt. You would need to *know* one way or the other about the future before choosing.

Make sense?

E

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Thank you Eric for the quick response. Makes complete sense. The 54 definitely seems to be a more flexible & future-proof option so I'll continue the search.