I'm not sure if I understand why measuring vertically and horizontally to a point on the saddle is any more difficult than measuring frame stack and reach? Why don't you use measure an angle and length to define the location of the top of the head tube? Measuring seat location "X-Y" should be just as easy as measuring head tube top location "X-Y". Besides, I don't see an angle measurement in this figure:

In Reply To:

accordingly, cockpit length is most easily, in my experience, measure v the saddle, likewise armrest drop. furthermore, what really MATTERS to cyclists is not the spatial relationship between the armrests and the bb, rather the relationship, or interaction, of the armrests, and bar ends, to the saddle. these interactions determine shoulder angle, and hip angle.

I'm looking at it from the standpoint of consistency in measurement. Yes, the saddle to pad location is important, BUT those can be either inputs or outputs. You can either measure them directly off of the bike in "X-Y" and then calculate the cockpit length and drop from those measurement...OR, you can do it like you prefer and then calculate the "X-Y". At some point those locations need to be translated into the "X-Y" coordinates in order to use them. My preference, and I'm coming at this from someone who deals with dimensioning and tolerancing on a daily basis, is to take the measurements directly from the chosen datum. That reduces errors in "setup to setup".

The dimensions you show can still be calculated and displayed as "reference dimensions", and would be the "quick and dirty" dimensions you could check to make sure things are where you think they are.

BTW, I have an idea for a fit bike attachment you could have made which would basically create a "fit bar", in other words, the aerobar version of a "fit bike". You could have made a device which allows you to position the pad locations and shifter locations in the X, Y, and Z coordinates (relative to the headtube top) and then you can directly read those coordinates off of the device and add them directly to the stack and reach coordinates read off of the fit bike. That way, you wouldn't need to actually stock a sample of each bar and stem type. You can merely have measured them once and then set up the "fit bar" to each candidate bar's particular coordinates (including the adjustment ranges). Same thing with particular combinations of stem lengths and angles, along with any spacers or head caps. You could fit someone on one of these fit bikes and be able to specify a complete bike/stem/bar/saddle setup without ever actually mounting any of them on the particular bike. What do you think?

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http://bikeblather.blogspot.com/

Absolutely, which is why crank length (along with the particular pedals, shoes, saddle and bars) should be CLEARLY noted on any fit coordinate sheet. They all affect the specific fit coordinates relative to the BB. They are part of the "assumptions" of the particular fit.

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http://bikeblather.blogspot.com/

"I'm not sure if I understand why measuring vertically and horizontally to a point on the saddle is any more difficult than measuring frame stack and reach?"

it's not. but end users don't ever have to measure stack and reach. they do need to measure their own fit coordinates. if end users had to measure stack and reach themselves, that would be pretty horrible.

the middle part of your post: asked and answered in our previous exchange.

the last part of your post: i welcome all new kinds of fit tools. we don't have a good XY tool yet to measure XY coordinates (like stack and reach). if dealers had a good XY tool, they'd be able to recruit some of their older fit bikes and press them into current service.

one thing, tho, about having various aerobars in stock and set up for use. to me, it's precisely like saddles. the only way to know if you like it is to sit on it. you could say i'm anal about my saddle ;-)

what i'm picky about is every "contact point". so, i want folks to try them, palpate them, not just the aerobar pads, but the extension shape, and the match of the extension height to the pad height, all of it. i want them to ride on that bar on a fit bike before they get sold that bar and that bar gets mounted on a bike.

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Dan Empfield
aka Slowman

"how tall are you? "
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I'm almost exactly the same size Jurgen Zack :-).....seriously - you may recall we were all together at Paula's camp in the early/mid 90s. You said I looked like Dirk....doesn't say much for my hair do.

5'101/2, 173 lbs.

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

it seems to me you're fairly evenly proportioned. maybe a little long in the torso? which would make your cockpit distance about right. maybe 1cm too long? my only comment, from afar, is that if i were forced to fit you without seeing you, watching your ride, or anything, it's that it seems your armrests are 2cm or so higher than they might otherwise be. and i wonder if that 1cm of tighter cockpit might allow you the correct shoulder angle that might then allow you to drop those aerobars another cm or 2.

then again, as you say, if your humerus is short, that's the explanation for the less than large armrest drop. but, if this is the case, your back is still going to be relatively flatt(ish), and affixing a goniometer to your hip angle while riding should yield an angle typical of a rider with a greater drop.

but even with the flatter back, the short humerus means a taller frame. specialized transition (not shiv), scott plasma, cannondale slice, blue triad. just, if it's a plasma, make sure you can get the saddle nose to +2.5cm.

but, as we shall see in the next installment, as lance says, "it's not about the bike." what it's about is "the bike + the aerobars." that's what will determine what you should be aboard.

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Dan Empfield
aka Slowman

http://www.youtube.com/watch?v=ESnVoXQwvLk

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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.”

harsh. but funny ;-)

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Dan Empfield
aka Slowman

Is there a ratio of stack:reach that says a bike is long/low or tall/narrow.

Back to the picture is worth a thousand words topic -

I "think" this would really drive it home for me:

Same guy. Same day. On these different set ups-
1. Bike that is the perfect set up for him (maybe Rapp)
2. Same model/brand but in the next size up. And next size down. Same fit coordinates
3. A bike that is built the opposite of their style (ie - if Rapp rides Long/Low how would he look on a Narrow/Tall bike with the same fit coordinates?)
AND - if the fit coordinates are the same across each scenario- what is the impact? (aero, power, handling,etc)

Thanks for your reply To my earlier post. Makes sense. Your stack and reach index for tri bikes is a fantastic resource. Talking road bike geometry for a sec, do you know where I can find stack and reach info? Most manufacturers don't list these on there geometry tables?

Thanks,

Will

A great thread. Small detail - I think you mean seat tube in this explanation? Might be confusing...

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Richard Melik | I work for the following companies | Zwift.com | Freespeed Bike Fit (UK)
Manager | David McNamee

"Small detail - I think you mean seat tube in this explanation?"

yup. seat tube.

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Dan Empfield
aka Slowman

"Is there a ratio of stack:reach that says a bike is long/low or tall/narrow."

it's not hard to divine. in very rough terms, if the stack of a bike is more than a third again its reach, it's starting to trend narrow/tall. so:

reach of 36cm x 1.33 = stack of 47.9cm
reach of 38cm x 1.33 = stack of 50.5cm
reach of 40cm x 1.33 = stack of 53.2cm
reach of 42cm x 1.33 = stack of 55.8cm
reach of 44cm x 1.33 = stack of 58.5cm

so, while a ratio of 1.33 or greater means it's trending narrow/tall, i think a ratio of 1.22 or smaller means it's trending long/low.

reach of 36cm x 1.22 = stack of 43.9cm
reach of 38cm x 1.22 = stack of 46.4cm
reach of 40cm x 1.22 = stack of 48.8cm
reach of 42cm x 1.22 = stack of 51.2cm
reach of 44cm x 1.22 = stack of 53.7cm

again, very general numbers. so, you take a bike that's got a reach of 42.0cm, if it's got a stack between 51.2 and 55.8 its a relatively mainstream bike, geometrically, at least as regards fit. let's see how some of these line up. here are bikes with a roughly 42cm reach, with their stack numbers, in order of long/low to narrow/tall:

kestrel airfoil pro size 52 reach 41.5cm stack 48.4cm ---- ratio: 1.17
kuota kueen k size 54 reach 50.3cm stack 42.6cm ---- ratio: 1.18
cervelo p3 size 54 reach 41.9cm stack 49.8cm ---- ratio: 1.19
cervelo p2 size 54 reach 41.8cm stack 51.2cm ---- ratio: 1.22
felt size 56cm reach 42.5cm stack 52.5cm ---- ratio: 1.23
orbea ordu size 57 reach 42.2cm stack 53.0cm ---- ratio: 1.23
argon18 E114 size M: reach 41.9cm stack 51.5cm ---- ratio: 1.23
qr cd0.1 size M reach 42.0cm stack 49.7cm ---- ratio: 1.26
trek speed concept size L reach 42.6 stack 54.1 ---- ratio: 1.27
specialized transition size XL reach 42.1cm stack 54.2cm ---- ratio: 1.29
cannondale slice size 58 reach 41.7cm stack 54.8cm ---- ratio: 1.31
scott plasma size L reach 41.6cm stack 54.8cm ---- ratio: 1.32
BH gc aero reach 42.0cm stack 56.0cm ---- ratio: 1.33
blue triad size ML: reach 41.4cm stack 55.8cm ---- ratio: 1.35

now, there are certain things to remember:

1. these bikes to not necessarily maintain these ratios throughout their size runs. for example, on our home page are write-ups of kestrel's 4000, and with its two tri bikes (the 4000 and the airfoil pro) plotted against trek's speed concept. the speed concept keeps to its ratio. the two kestrels do not. this is not a bad thing, it's just a notable thing, and it gives kestrel's retailers a pair of geometric styles to choose from when fitting their customers. just, neither model keeps to a single style. they're BOTH moderately trending long/low in their two largest sizes. but in their smaller sizes, the 4000 trends narrow/tall to midlin'. the airfoil pro is long/low in its smaller sizes.

2. this is a lead-in to the next class, so, get ready: it's not the BIKE that determines the ratio. it's the BIKE + AEROBAR that determines the ratio. for example, if you take a p2 and put a 3T aura on that bike, and if you take a slice and you put a vision clip atop that bike, and you do this in the sizes listed above with the 42cm reach, you now have two bikes that are almost exactly the same height to length (assuming the stem length and pitch is the same on each bike).

so, don't get too hinky about the FRAME, rather, consider the entire construct aboard which you'll sit.

one more thing: what's the most mainstream bike on that list? trek speed concept. in every size, it's right smack dab in the middle. why? because trek plotted every bike in the market, and designed its geometry with the prime inputs as stack and reach. trek made a wager, that if its bike sat in the middle of the pack geometrically, it would fit as many customers as possible, and it would inoculate itself against any charge that its bikes were geometrically problematic. it wagered that if it simply erased that as a concern for as many people as possible, then it could concentrate on its narrative of superior aerodynamics.

that established, it's now up to bontrager to make aero bars that allow the entire construct to fit as many people as possible. in other words, bontrager has to do what trek did: make a geometrically mainstream bar; or it needs to make two bars: one high profile and one low; or it needs to make one bar that can be adjusted high or low profile. did bontrager do this? this spring we'll be reviewing aerobars and you'll find out. but in the next class, i'll equip you so that you can determine this yourself.

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Dan Empfield
aka Slowman

Do you offer fitting as a service?

Mike

"Do you offer fitting as a service? "

no. our FIST school teaches retailers how to fit, and manufacturers how to design and spec their bikes to make sure they're geometrically correct. i don't fit. but, we have two instructors who teach here with me. one is rappstar, the other is jt lyons at moment cyclesport in san diego. these guys are each very knowledgeable, of course, they're also each university trained engineers, and i chose jt to be one of my two FIST instructors because when he took the course he was the biggest pain in the ass ever to set foot on the compound property. this, because he asked the hardest and the BEST questions. he really got it, to the point where he saw through every flaw and i reckoned that if i just absorbed him into the system he'd help me fix any flaw. likewise jordan, well, you know what a pain in the ass he can be, so, with these two ass pains FIST as a system has continued to gain strength as a protocol that stands up.

i'm am absolutely convinced that if jordan and i each independently fit 10 people, 8 or 9 of those people would end up with fit coordinates within 5mm in every axis. jt likewise is going to be very close, but, jt sees a lot more people on a day to day basis than do jordy and i, because jt owns a retail store and fits people all day long. jt also has a new guru dfu bike, pretty neat.

i don't know if jordy will fit people, other than the pros who go to him. jt of course does. the two people i'd recommend most highly are, of course, these two. i don't know if tom demerly is fitting people over at trisports in tucson. i'd recommend tom. i like colin o'brien at cronometro up in madison, wi. there are plenty of good fitters out there.

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Dan Empfield
aka Slowman

I'm wondering if Jordan and JT appreciate you using the term "ass pain" and the acronym "FIST" in the same sentence in reference to them.... ;-)

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http://bikeblather.blogspot.com/

Kevin Riseborough - flying wombat here on ST - is in the Phoenix area. Has taken the FIST workshop at least twice and every time is a major pain in the ass (in a good way) and also demonstrates over and over that he "gets it." I've sent several folks to him, and they've all been happy. I'd add him to Dan's list of top notch fitters who've been through the FIST program and really buy into it and fit according to the methodology we teach.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

I'm a little late to class and I hope I'm in the right room...

How does saddle choice play into the "saddle nose to extension"? Specifically, I sit differently on different saddles. My hip angle changes based on which saddle I am using therefore changes my coordinates.

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******************************************************
Well I believe in God, and the only thing that scares me is Keyser Soze

Rappstar,

Is there anyone you would highly recommend in Texas. Closer to Austin, San Antonio, Corpus Christi, preferably South Padre Island or Rio Grande Valley. Thank you.

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Jehovah and family unity above all.

"How does saddle choice play into the "saddle nose to extension"? My hip angle changes based on which saddle I am using therefore changes my coordinates."

then, your fit coordinate is tied to a particular saddle, just as it's tied to a particular crank length, and maybe a particular cycling shoe.

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Dan Empfield
aka Slowman

I know that ATC has sent four folks to the FIST workshops, but I do not have any personal experience with them beyond that.

I really don't want this thread to turn into a "who do Dan & I recommend for fitters." That's largely why we added the additional field for "fit methodology followed" to the bike shop database. And that's why we put up details about exactly what the FIST process entails. And THAT is why we are having this thread. We want you to be educated about what a fit should entail. Then you can go ask the person who wants to sell you a bike what the process means to them. When those two things are in agreement, THAT is the fitter I would highly recommend.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Rappstar,

Point well taken and I apologize if you feel I in some way put you on the spot. My reasons for asking were a bit selfish. Obviously, Dan and you are well respected in the community for numerous reasons. So it stands to say that your opinions around here carry a lot of weight. But you're right, that is why we're having this thread. Hopefully, to educate us well enough to ask the important questions and form our own opinion about the fitter's knowledge.

I feel Dan has helped us achieve this already. A great deal of thanks.


-J

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Jehovah and family unity above all.

Thanks Dan....If Herbert ever gets his Scott finished, and since he is just a few minutes away, maybe I'll get to try it!

Thanks!

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

The one question in this thread I most wanted to see an answer to is Cheddar's - I have a position that is pretty comfortable and seems to work pretty well, but I suspect that perhaps it could be "better". How do you know when your position is optimized, rather than just acceptable? I recognize that this requires striking a balance between different factors, namely comfort, power output, and aerodynamics, and that the appropriate balance is going to vary between individuals. I also recognize that aerodynamics is going to be somewhat difficult to determine on a fit bike (beyond the "eyeball windtunnel"). But if I assume that there is a small range for each measurement within which I will be equally comfortable, what is the protocol for figuring out which position is the "best"?

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__________________________________________________
The plural of anecdote is not data. :-)
- Andrew Coggan

My biggest issue now with S&R now is how to figure out the STA.

If I understand everything well for a given individual, a steeper STA means forwarding and lowering the arm cups. However, it seems to me that the TT position is one that you grow into, and as you get more miles in the position you can go lower and steeper. It was certainly true for me and my road position where I was able to get into a more aggressive road position after many miles.

So say one person starts a 76deg STA but grow comfortable into a 78-80deg STA. That means changing the cockpit contact points, but can you accommodate this without needing a new frame, since S&R is now different? If you can achieve that with just changing the cockpit components (lower aerobars) without an extremely long stem, how do you choose the optimal frame that will allow you to slide forward over time?

OK, so I get S&R, and I get its relationship to fit coordinates (my body on the bike). I also get that the common sense end result is a frame whose S&R matched with their 'right' aerobars provides that 'best match' form me (and the right crank size, stem within tolerance, seat adjustment within tolerance, etc). Here's a potentially irrelevant question: If my frame is too small and my setup is beyond reasonable tolerance in order to make it work for me, do I gain comfort and speed with a larger frame (assuming the coordinates are correct). Does the larger frame, with its longer (apples vs apples) wheelbase provide a fundamentally faster platform per watt? Just bitch slap me if this is way too off-topic or random, but this relates to my specific issue with my current frame. I also love my saddle, and it's the only component I'm not willing to swap out.