Thanks. Trent Nix did the fit. Cranks are 150mm.

CdA measured by Chung method at 0.223.

I appreciate the inputs but I feel my question is being lost in the noise...


Did you bring this bike to the fitter or did you purchase this bike AFTER a FIST fitter prescribed it as the ideal solution for your body?

Assuming the first scenario, WOULD the FIST fitter have recommended a larger bike to bring your elbows closer to the head tube centerline (magenta line below) if you were purchasing new? THAT is my question... That is my only question.



Assuming we all get to play armchair fitter... If you are comfortable there, from what little I can see it looks good. Maybe a bit forward on the saddle and a bit round in the back, but I am not a professional and I don't know your athletic history/what distance you are training for etc... IMHO as long as setup/technique isn't obviously going to cause harm (ie bad joint mechanics), comfort is king.




I'm new her so you don't know me, my capabilities or what I'm working with. Why would you presume to know those things? I have not asked for a size/bike recommendation. As stated I'm not trying to fit her on an existing bike, I have finally convinced her to purchase new.

This is not witchcraft. Is a fit rig handy? Yes for a professional, tools like that increase speed and accuracy. Is it required? No. I have more then adequate measuring capabilities, a free database online full of bike geometry data, a robust cad package and the requisite hand tools to build/adjust the bike.

My wife is tallish (5'8") and has a long torso. She is also not going to Kona, does not want to spend $5k on a bike and has been happy/successful with my fits/bike modifications thus far. So have the other three people I've done fits for.


But why is that? Perhaps that is your personal experience because you are too forward on the bike aka its not big enough for you to keep your elbows/weight further back.



For funsies I had my wife meet me at Trek tonight after work. The Trek Fitter stood her in front of a touch screen/camera deal and took her inseam/height measurement and POOF the results said 'you are perfect for a medium Speed Concept'. Possibly but my calculations regarding this elbow placement issue indicate a large would be a better fit (I looked up the dimensions prior). So I asked them to put her on a large instead. Fitter's helper Skippy was instructed to dig out a large and get it setup on the trainer. I convinced Skippy to let me have the tools instead of waiting for Capt. Fitter to finish with the last customer and I had her comfortable and talking about fine adjustments and how much better the hip angle felt in less then 10 minutes. No measurement tools at all, just eyeballing body position and watching a few pedal strokes. For what its worth, the Fitter agreed he tries to keep elbows close to the head tube centerline on new purchases but he cited adjust-ability not stability as the main reason.

I bought the frame first. It's a used frome, obviously. The next size up is a 57, and I never found one. So I pounced on the 55.



I completely understand your question. It's just the wrong question. Asking it betrays a lack of understandimg of what matters.

I don't know what Trent would have recommended. He's still around on the forum, so he can comment if he chooses. Or Eric is welcome to comment. It's a 90mm stem, which is pretty short. As it is, I'm stable in full aero at 40mph.

My pad staxk/reach are:

Pad stack: 615 (back of pad)
Pad reach: 500
Saddle height: 780
Crank length: 150mm
Seat: ism pr2.0
Eff sta: 77*

I have plenty of hip angle so, I COULD slide back 2cm. But, I'm comfortable.



You'll forgive me if I trust one of the best fitters in the country, and don't really care what some random interneter thinks.



No one said its witchcraft, but it is a skill, and it is NOT based on static geometry. Just because your an ME with access to 3d CAD tools, doesn't make you a qualified fitter. The fit quality is not from the tool, but IS from the fitters training, experience, eye, and knowledge.



This is not my experience. My tt bike is 1000x more stable than I was in aero on my road bike. I can stay there comfortably at 40mph, whereas it was a matter of nerve at anything over 30, I always lost my nerve at 35pmh on my road in aero.

Good luck. You don't seem interested in advice from people who've already done this. So, I'm out.

If you’re interested in a Cervelo, there’s a thread for asking for Cervelo fit advice on this forum.

Best way to get the right bike is a pre purchase fit from a reputable bike fitter

---

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.”

You are going about it backwards

---

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.”

I will try one more time...

Hey professional fitters/people who fit their own bikes: Given a person's anatomical stack/reach, if those dimensions fall between two bikes, is it better to go with the frame that is a little on the plus side or a little on the minus side of reach and why? (hint, I have a theory)



I suspect had you found and purchased a 57, your expert fitter would have put you in exactly the same position you are in now anatomically. The only difference would then be where you elbows land relative to the fork tube ie where your biological stack/reach lands on the bike's geometry yes? That begs the question, what prompted you to seek a 57 in the first place?


As you should... Jimatbeyond offered his/her opinion I figured I would offer mine. At least my opinion is backed by some limited analysis, so maybe I can be elevated to 'interesting random interneter'?



So far you are the only one even contemplating the question and engaging in higher level conversation...

Anyone familiar with Blooms Taxonomy? If you are happy paying a professional to do a task so you can focus energies elsewhere, go for it. I am seeking a higher level of understanding on this subject. You are correct, I am not interested in advice from people who have simply been fit and are only capable of puppeting 'go to a professional fitter'. I am interested in analytical thinking and advice from people who actually do fittings, understand the specifics enough to comment intelligently, or at a minimum are willing to engage in the pursuit of knowledge.

You and others were fit by a professional. Great. Do you know why the fitter set you up the way they did? What compromises were made? What factors were prioritized in YOUR fit? Why don't you?

Furthermore, how many pro fitters have degrees in kinesiology, exercise science or biology? How many are certified/practicing PT's? All of the fits I have done have been validated by professionals in these fields. The last fit I did, a physical therapist was literally telling me what they wanted to see for their patient and I was playing mechanic and offering advice on gear. All three of us learned a lot that day!

How many pro fitters offer free lifetime re-fits/adjustments? For those I've fit, I make changes anytime they want/need one. Usually as injuries heal, gear is upgraded or strength increases during season.

I have no desire to become a pro fitter... However, I do enjoy being a high functioning hobbyist who helps out friends and family in trade for a good bottle of wine.

Please elaborate.

If you have been following along, wife has never been on a 78 degree bike, only a too small road bike. I'm taking her current fit and complaints into consideration for the next bike. I don't have a fit rig but I do have CAD. Her current stack/reach doesnt help all that much if we are changing crank arm length and seat tube angle... So I modeled her in the current situation AND on the 78 deg geometry, placed her anatomy in a baseline anatomical position, calculated new stack/reach and a list of frames.

Assuming you are fitter and my wife walks in with the info provided, you are gonna laugh at the old fit and say its useless, set your fit rig at 78 degrees, put her in a position you think will work and ask her how she feels, right? I did the same thing, but instead of a fit rig I used cad and 'borrowed' bike.

I am buying a NEW BIKE. I am not trying to arbitrarily place her elbows on an existing bike in an attempt to fix twitchyness or fit the human to the bike.

Its a detail/nuance/technical question. Given a 100% custom carbon fiber layup build for a factory team backed pro rider, where any component can be in any position, where would the fork tube centerline fall relative to the rider in this idealized, mythical unicorn hypothetical fit?

I was considering a cervelo 56 or 58 but after getting some video of her on the Trek and her initial feedback, I think the 56 is going to be ideal

what could you do with a completely blank slate with CAD?

---

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.”

Aside from design a fully custom carbon bike, then the moulds for said custom bike (not fully within my abilities) OR fabricate a custom aluminum frame in my garage (completely within my abilities)?

Well, during morning coffee I can take body measurements and current bike measurements and verify 'close enough' accuracy of current setup.




Then I can change crank arm length/seat angle and adjust body wireframe to be in a reasonable starting position and take stack/reach measurements from there. (note: I did not change the rest of the bike wireframe so dont freak out)




Granted I could have done all of this 2d work in an old copy of AutoCad or even with grid paper and a protractor but I like working in SW...


THEN, because we don't have any triathlon stores in the area and the only local bike shop that even has a tri/TT bike is Trek, I can take her down there and put her on a bike that is at least close to my proposed sizing and see how she feels and how it looks in real life. (this is with one eyeballed seat/bar adjustment)




Way better then 'whats your inseam and height' no? Trek 'computer sizing' called for 24/18mm less stack/reach.

How'd I do Coach? Am I still in reverse?

The great thing about a Trek SC is that they’re super versatile fit wise, so you probably can’t go wrong, although based on that pic you’re risking going a size too small IMO.

But as my grandfather always said, use the right tool for the job... the end point in your process is the start point in our process here, if you use a different tool which is orthodoxy.

IOW, the tool you’re choosing to use is leading you down the wrong path.

You’re doing things right but you’re not doing the right things.

---

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.”

Trek SC was not purchased. It was used as a validation tool. Remember, she has never been on a 78 deg+ bike AND I'm verifying my work. Trek wanted to put her on a medium, this pic is of her on a larger per my request. I'm going with a cervelo 56

end point in my process? Beginner athlete finally listens to friends and comes to you for a fit and you determine the bike is all wrong; what process do you use to prescribe a new bike?

Once the new bike arrives, real fitting begins, yes?

No. no no no no no no no no no.

The real fitting begins BEFORE you buy the bike, on a fit bike with a good bike fitter.
If you want validation you take the video supplied by the fitter and post it here for peer review.

THEN you buy the bike best prescribed by the fit, and all the fitter should need to do is adjust it to the specs from the fit bike. Shouldn't need much more than a final check after that if they did their initial job properly.

No.

More nuanced, it depends on which tool you use... if you use CAD or whatever proxies Trek is using to prescribe bikes then yes, the fit starts when the bike arrives and there's a good chance it's the wrong bike, and then you'll have to start over.

But if you do it my way, and use the right tools, a camera and an eyeball and athlete, and measure comfort power and aerodynamics instead of measuring angles and such, then the fit starts *before* you buy the bike.

As MattyK has said, a good proxy for the eyeball/camera/power/comfort/aerodynamics method is by posting a picture here and having it peer reviewed, because community and orthodoxy are both powerful tools.

Posting CAD angles isn't helpful and of course CAD outputs what it outputs... angles and measurements. Pre-purchase bike fits or community peer reviews output bikes that fit. Brands, sizes, cockpits, cockpit configurations, crank lengths, saddle choice, saddle angle, saddle setback, etc.

The second way is more accurate and more efficient.

It's like dating... doing the fit after you buy the bike is an arranged marriage. You have to try to make it work, and sometimes, randomly, it's a great fit. Doing the fit before buying is like getting to know someone first and seeing if they're compatible and if there's a connection.

---

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.”

I think you meant to say that the OP should post a video here, rather than a picture.

You are right of course, but i think one can *size* a bike from a picture if you know the variables and have an internally consistent fit philosophy

---

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.”