OK it's like this: you're fitted here to a road bike with a saddle height of 712mm and an effective seat tube angle of 75 degrees. You're going to switch to 165mm cranks (at least, hint hint) which gives you an effective saddle height of 720mm again at 75 degrees. At 80 degrees, you'll still have the effective height of 720mm (although you'll probably have more saddle tilt) but you'll be 60mm further forward than 75 degrees. So, instead of a rough "handlebar" stack and reach as a proxy for pad stack and reach of 636mm and 420mm as listed, you'll be closer to 636mm pad stack and 480mm pad reach.

So, you've been riding a Giant size medium and you'd assume you'd be a size medium in a tri bike but you'd be wrong. If you went with conventional wisdom from back in the day you could be even wronger because in the olden days the rule of thumb was tri bike = one size smaller than road bike. However you, the enlightened Slowtwitch reader, know that you have to be able to get long to be comfortable and thus you could fit on a size 56cm *or* 58cm P-Series or a size L and really practically a size XL in the PX series bike.

I'm harkening back to the olden days because I want to assuage your doubts that are arising because you thought you were a 54cm and I'm telling you you're a 56cm or even 58cm. There's lots of inertia and received wisdom from back then that's still in circulation, IOW there might be malware installed on your operating system that's pre-programmed to give you that sense. Thankfully you installed the full antivirus suite for your OS in that you knew to come to this thread.

So, to sum up, 56cm unless you absolutely know for sure you're going to have a State Time Trial position in the future in which case you might need the length of the 58cm, but that said the P-Series is way more versatile than the P5 in fact, and you might never notice even with a 56cm. Also, I may be overestimating, so that is another data point for the 56cm.

Make sense?

Eric

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Hi, thanks for reaching out. So glad you got a pre-fit.

You're very similar to the previous guy, but just different enough that you only have one option whereas the other guy could go either way. With a pad stack of 667mm and a pad reach of 489mm you're very squarely off the charts for the 56cm and in the center right quadrant of a 58cm P-Series. You'll have room to grow if you get longer or lower in the future too.

Make sense?

Eric

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Hi Eric,

I am still on rim brake, thus considering a P3 P2 from 2016 or after. Maybe the previous version if the bargain is worthy.

Anyway here are my measurements
saddle height : 82,5cm
pad Y : 690
pad x :535
Inseam 89cm
height 185cm

Thanks for your help

Hi there, thanks for reaching out.

You are off the charts long and low, sort of like me coincidentally. With a pad reach of 535mm a size XL PX series bike would fit you, but you'd have to come down to a pad stack of 640mm compared to your 690mm. At 690mm of stack, you'd be at a reach of 520mm.

I guess what I'm saying is that you're slightly off of orthodox with respect to your stack and reach relationship, not the fact that you're off the charts. I think a size 61cm P-Series bike would work great for you too in addition to the XL PX. s

Make sense?

Eric

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Thanks Eric, it s true that I'm a bit unorthodox. I ve got long legs and relative short torso for size, and long arms as well!!
The trouble I'm in at the moment, to choose a frame, is that I've bought my bike before having the bike fit. By the way my bike is a look 576 XL.
Maybe would it be better to start over the process from scratch, doing another fit with all the measurements and then choosing an adequate bike?

I think the PX in XL or the P-Series in 61cm would be adequate.

Eric

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Hi Eric,

Pad stack is 770 (15 degree rise - front of pads is 755)
Pad reach is 553 to back of pads
Seat height 854.
Gap between pads (inside to inside) 147

I’m a shade under 6’5” with longer legs proportional to height, particularly lower legs. Currently riding a 2012 Specialized Shiv S-works XL.

Ideally interested in P5 but since they don’t make an XL frame I’m doubting that’s possible. Otherwise just the fastest/best frame that would fit me.


Thanks for doing this,
Greg

Hi Greg, thanks for reaching out.

With a Pad Stack of 770mm and Pad Reach of 553mm you'd be off the charts for a 58cm P5d which maxes out at 735mm stack and 490mm reach. I could not ride this bike either.

You said "ideally" a P5... why is that? If you tried the PX in size XL you could get much longer with equal or better aerodynamics, depending on your storage and hydration strategy.

There are also some things you could do with aftermarket mounts, extensions, and super extensions to get a little more reach. The super extensions would also have additional stack built in. It would just be a math problem at that point, plugging and playing the various combinations of aftermarket parts until you found the right combination of stack and reach.

Make sense?

Eric

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Hi Eric,

Actually, I’d be interested in the PX. I had forgotten that it was out there. Available used only at this point, correct?

I pretty much just do Sprint triathlons and use only the built into frame water storage on the Shiv. That is my ideal.

Thanks again,
Greg

Hi Greg
Buyer for a tri shop here! For 2022 the PX is only available as a frame set. Doubt there will be many available as Cervelo is “allocating” their bikes this year due to ongoing supply chain problems (gave us 1 PX frame set size M for the 1st two quarters of the year).
Basically you’re gonna have to look around!
Good luck!

Hey Eric ,

6ft currently ride 2014 p2. 58cm 105mm stem -24 degrees .
15 degree tilt-
. X: 470 y:670. Do have open tririg cups so reach maybe more. also can drop some. Looking at 56 p5d vs 58 p5d. If I could find a hydraulic groupset may look at p series( I have set of alpha one bars)- fit for that 56 vs 58. Thank you

Hey, thanks for reaching out.

I mean, you're smack dab in the middle of the box for a 58cm P5d. A 56cm would work, with 25mm more reach that you could play with. Heck, even a 54cm would work but I don't recommend it.

I guess it comes down to what do you think your fit will evolve to in the future. If it were me, with an absolutely fixed position that will never change again, I'd do the 56cm. That said, I bet if I saw a pic of you on your bike I'd be pushing you toward the 58cm... just a hunch.

Make sense?

Eric

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any news on when Cervelo will distribute S5 zero offset seatpost? i am waiting since more than a year and yet no news.
how is this possible? no where in the world i can find a shop selling it

I don’t have visibility on that sorry.

Eric

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Further to what Eric said - once the tilt is factored you're in the centre of the reach range for the 58.
Would definitely go 58 for stability

Cervelo Seatpost S5 SP20 2019 0mm Offset SP-SP20-ZERO

In stock in New Zealand. So they have shipped some out
I checked shipping to Switzerland and it's not too bad (unless you want it next week)

please post the link i order immediately

Thanks for the info mate.

E

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Longer is always better ;)

E

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Dear Eric,
Another of the chart long and low for me. Currently ride p3c with slammed stem, -17 deg 130mm, 3T Aura with pads on the bar and extensions below the bar...
Pad x 515mm back of pad
Pad y 565mm bottom of pad holder.
Is there a way you can match that with any of the new bikes?
Thanks

Hi, thanks for reaching out.

With a pad stack of 565mm and a pad reach of 515mm you are a 58cm P5. You might need to get extra large aftermarket pad holders to give you a little extra reach but you are right at the outside of the envelope for the P5.

The PX is even longer still, and if long course is your thing then you might try to find one quick.

E

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Eric how do you realize that low stack height? When i look at the fit graph, the p5 58cm lowest is 615mm...

My mistake. I entered 665mm. You’re right you’d have to come up to 615mm for the 58cm… I’d need to see a picture or video of you to comment further.

E

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Hi Eric,
Back from holidays, took a picture while on the trainer hope that works.

Sure can you post it?

Thanks
E

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Eric Reid AeroFit | Instagram Portfolio
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