Hi Eric,
Thanks for doing this. I enjoy reading your analysis on everyone.

I have been riding the same bike since I got in the sport 6 years ago (QR CD.01). I bought it because it was a good deal and probably not the best fit for me. When I had it fit, the fitter says it was long for me (5'7, 145lbs). I also have a bad lower back. We have it stacked and stemmed up for those issues. Definitely not the most aero. But I feel comfortable on it. I tried the P5D which I loved, except for the base bar. I felt very limited climbing with it that low, it will probably irritate my back, and it does not seem to be able to rise. The P series looks better and more adjustable for me. I tried a 51 and it felt awkward. I may need a 54? Would I be better of just getting the frame and customizing for fit of cockpit and crank lengths for example? I have tried to attach my retul fit and a picture of me riding. What is a remote fit you mention in a few posts? Thanks for the thoughts, time and recommendations. I am ready for a new bike! Todd

When another fitter says says a bike is too long for someone, I usually start salivating at the thought of someone being on a properly sized bike! Let's have a look....

Looking at your bike fit photo, you seem upright and a little slack, IOW you're not taking advantage of the longness and lowness of the QR CD.01. This could be for a number of reasons, not least of which it's an oblique angle photo and not the best perspective, but perhaps it's because you haven't had the postural coaching and saddle choice coaching that would enable you to do what a time trial allows you to do with your body. Even with a bad lower back (which I have as well), you can get into a reasonably orthodox and aero position if you keep your back neutral and roll your pelvis forward instead of bending your lower back to get to where you need to go. This effectively lengthens your upper body, and thus long and low frames come in handy when you have this posture. The key is the saddle, and how the aerobars catch you.

With a Pad Stack of 682mm and a Pad Reach of 411mm, your current Retul fit numbers, you're an odd duck, something is up. Very upright or high Pad Stack for someone of your height. Off the charts high for a 51cm P5d and off the charts high and left (ie. slack) for a 54cm P5d. You're even too high for a 56cm.

I hear you about the lower back issues, and I hear you about the basebar, but I feel like putting a band-aid on those problems is a side issue, and we need to get to the root of the issue, the cause of what's going on. There is no reason why a lower back challenged person (remember, me included) can't have a good TT position with the right saddle choice and sitting and postural coaching. I'm also not buying the theory that the P-Series is more adjustable or more appropriate for you, not for the reasons you're giving. Follow me here...

For example, if you came down 2mm to 680mm and added 22mm (not even an inch) to your current position, you'd hit the very upper very left quadrant of a 56cm P5d. This is very easy to do, just with posture, and if you slid your saddle forward to help out it's even easier.

To hit a 54cm P5d, the very upper left quadrant, you'd need to lower your Pad Stack to 662mm (18mm, again less than an inch), and add 7mm of reach to 418mm, which is barely even noticeable. Between the two options, ie. adding an inch of reach to hit the 56cm P5d or subtracting an inch of stack to hit the 54cm P5d, the reach is an easier as, unless you went with shorter cranks in which case it would be a wash.

At any rate, after my hypothetical adjustments to you here, you're *still* at the very upper very left edge of the fit charts, for either a 54cm or 56cm P5d, and that's not something I would call orthodox. You'll be the same on a P-Series. Let's address your fit first and your orthodoxy and see if we can't crack the code on the saddle in order to get your back in a neutral posture effectively lengthening you and lowering you. The more I think and write about it the more I think short cranks and a saddle intervention and postural coaching are what you need.

(I should add here that a EX10 mono-riser from the P3x is something you certainly should do, it adds some reach flexibility fore and aft as well as a native tilt function, which will help you)

Finally, stay away from a 51cm bike at all costs.

Make sense? Shoot me a PM and we can talk more or I can find you a fitter. If I had to go with my gut I'd say get the 54cm P5d with the EX10 tiltable mono-riser.

Eric

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Ok. I sent you a PM to further discuss this. Thanks!

Dear Eric

I own a Felt IA 4, in 51 size, and I´m looking for a better fit. I have the oportunity of buying Cervelo, I love the new P5, but price and also availability in my country is making move toward the P-series, basically, a P-series frameset and later customize it. My fit cordinates actually are:

Pad Stack: 596mm
Pad Reach: 428mm
Pad width (center to center of pad): 228mm

I was wondering if a size 48 would be better for me, I´m 169cm tall.

Thanks in advance!

Horacio

Hi Horacio, thanks for reaching out.

You *could* fit on a 48cm, but I think I'd put you on a 51cm P5d or P-Series with those fit coordinates. On a 48cm you'd be in the upper right quadrant of the fit adjustability range, whereas on the 51cm you'd be center left, with room to go lower or longer if need be. You wouldn't have that reach flexibility with the 48cm.

Make sense?

Eric

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Dear Eric

Thanks for your quick reply, I perfectly understand what you explain. I would like to go lower, that´s why I was thinking of getting a 48. I attach a photo of my current setup, aerobar has no risers, it´s at it´s minumum, so you can better understand, cranks are 165mm



Best regards

Horacio

You've got a very workable position that really doesn't need much in terms of stack height changes but more in "postural" changes. IE, if you properly turtled your head and shrugged your shoulders your current stack height is fine. You'd need more reach to accomplish this comfortably, and probably a little bit of tilt. You could even come "up" some in terms of pad stack in order to effectively *lower* your head which I know can be a bit counter intuitive.

After seeing this pic, I'm comfortable saying that you'll be fine on a 51cm. Heck, with adding 15mm additional reach to your current numbers, which I think you absolutely need, you could hit a 54cm P5d with the flexibility to go 20mm lower, which I don't necessarily think you need. The 51cm P5d should be perfect for you.

Eric

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Dear Eric

Thank you very much for your advice, I´ve changed those extensions later and put on Zipp vuka ones with 70mm height, because I wanted a more relaxed wrist possition. Regarding reach, the original retul fit posture is more backwards, like 10-15mm, but when I race or do some power intervals I tend to go forward, I dont know why, it´s feels natural to me to grab strong the extensions and move forward.

I´ve 3d printed some spacers to tilt a bit the extensions, as the Felt bar does not allow this by default. Here is a more current pic, I´ll raise the pads a little to try out what you´ve told me.



Best Regards

Horacio

Hello Eric,

I'm looking for a Cervélo P-Series, but I don't know if my frame size is a 51 or a 54.
I've got 178 cm and 81 cm inseam.

Thanks

The Bike Fit in my Argon 18 E-117 Tri+

hi, thanks for reaching out.


With a Pad Stack of 628mm and a Pad Reach of 415mm you're in the very upper left quadrant of a 51cm P5d, and similar on a P-Series, but you're a bit unorthodox, sort of upright and I'd be concerned that once you grew into your fit you'd be needing a 54cm. I haven't seen a picture of your fit obviously, but I'm guessing with more saddle and posture coaching you might move toward the center quadrant of the 51cm.

The great thing about a P-Series is that you can put on a shorter stem and the cockpit is very adjustable to begin with. I'd go with a 51cm using extension and pad risers to get you to 628mm and not stem spacers. If you're thinking your position is one that will evolve and that you'll grow into, we can talk about what it would take to do a 54cm bike.

Make sense?
Eric

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Hello Eric
I would also like to ask you about bike sizing.
I'm about 5'9" tall. I'd like to buy new P5D. Right now I'm riding custom bike frame in size 50 (as it's written on the frame) with long stem, with great angle and a lot of spacers over the base bar.
I've made a bikefitting with the results of:
Pad X: 660
Pad Y: 432
with a note that the reach should be a little be longer (I've had old, shorter stem).

I was trying to be more aero and in this year I experimented with my position. I feel that's a little bit faster, but I'm struggling with my lower back pain on the longer rides with 70.3 effort (and harder).
I measured current setup, you can see it on the photo, and the numbers are:
Pad X: 670
Pad Y: 460

To be honest I thought that it would be a choice between 51 and 54 size. I've ridden a while on a P-Series in 56 size and it felt just too big. When I'm typing the current stack and reach it says 56, but typing the bike fitting coordinates it's 54.
What do you think?
In the future I'd like to go a little bit lower, so I don't think that I would need more stack margin. But all of it depends if my lower back will cope with it.

Regards, Adam

Hi Eric,

Thank you for your reply.
I will go for a 51.........

Hi Adam, thanks for reaching out.

I'm not sure which photo you're referencing in your post. Also, you're giving me two fairly different reaches, 432mm and 460mm. Can you confirm?

That said, with a Pad Stack of 670mm and a Pad Reach of 460mm you are in the upper upper middle quadrant of a 56cm P5d or upper third left quadrant of a 58cm P5d. On the 56cm, you'd have an additional 20mm of reach flexibility until you're maxed out on reach.

Curiously, at a stack of 670mm, 432mm is off the charts high and left, very unorthodox. I'm liking the 460mm reach much better. Often, when getting "lower" or "more aero", people tend to round their lower backs rather then rotate their pelvises to get lower. This can be due to improper saddle, correct saddle sat improperly, or improper postural coaching. Also, cranks too long. Long story short, to alleviate your low back pain, try to keep your spine in a neutral posture, and do so by rotating pelvis forward and not rounding lower back. Examine saddle and crank choice to make this happen.

My judgement? I'd be curious to see the photo you're referencing. You are absolutely NOT a 51cm P5d and probably not a 54cm, at least not at 670mm and *barely* at 660mm. You could make it work at 660mm, but it's not optimal. I think a 56cm P5d is your best bet

Make sense? LMK if you understand and if you have a picture.

Eric

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Sorry, the photo hasn't been uploaded. Here's the link: https://imgur.com/a/ErPB1es
This is the setup with 670 stack and 460 reach. On bikefit the reach has been set to 432mm, but with the note that it could be more, but back then it was limited by the short stem. Right now I replaced the stem for the longer one and I extended the reach to 460mm. I also adjusted pad stack and seat height, but I'm not really sure I did it correct. Could you check the photo? I think it would be good to lower the pad stack. I feel really weird about thinking that the 56 size will be fine, because I always rode 50-54 sized bikes, but it seems that the Cervelo charts are rarely wrong, aren't they?

Regards, Adam

This is a very serviceable position. At a minimum you want the 56cm P5d and I could even make the case for a 58cm P5d, but that would probably require you to see me or another like minded fitter in person to explore that option.

Just keep in mind that the 56cm P5d maxes out at 485mm reach. This should be plenty for you.

Eric

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Basing on your experience, do you think I can stay with current reach and maybe in the future going further forward? Definitely not making the reach shorter? I didn't mention, but I can put an EX10 riser (probably I will do it anyway to try riding with some bar-tilt).

I would definitely visit you personally, but it's hell of a travel :(

Regards, Adam

Hi Eric

I recently came off my bike and broke the frame, insurance is paying out for a new frame and was thinking of getting a Cervelo PX Series

I cant figure out what size I would be, and I do not have my Pad X / Pad Y measurements

I was on a medium Giant Trinity Advanced (2016) and had a very comfortable bike fit.. not sure if this helps?

hmm... got a pic of you on your tri bike in the aero position? What are your stats?

thanks,
Eric

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Hi Eric

There was a picture attached to my original post - is it now showing?

I am 1.78m tall, what other stats would you like?

Inseam?

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80cm

So I would classify a Giant Trinity as a "narrow-tall" bike, in that in a size M, the stack is 539. This stack for Cervelo would be at least a size L in the PX series or size 58 in the P5d. That's because Cervelo falls in the "long-low" category of bikes.

So, you could safely fit on a size M PX series bike, and perhaps even a size L. A "slammed" size L PX comes in at 593mm... looking at this pic of you, it looks like you're at about 640mm of stack. A Giant Trinity size M frame has a frame stack of 539mm and a frame reach of 417mm. So, you look to be about 620-640mm stack and 437mm of reach. A PX maxes out at 487mm of reach in your stack range, so you see the dilemma... get a bunch longer and you'll wish you had a size L, get on the size L and get just a little lower and you'll wish you had a size M. Based on the length of your stem, and the reach I'm estimating, you'll still have 50mm to play with.

To sum up, you're a size M. I don't see you needing to get much lower, rather, just need tuck that head in or get some new head posture coaching.

Make sense?

Eric

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hi, are you tracking on my last response?

E

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Sorry i missed the notification of this - Thank you for the advice, i think I will go with the Medium