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FIST 301: Are you ready for grad school?
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at this point, what you should understand is as follows (and if you're coming to this late, best go back and read an earlier thread first):

1. when i talk about "stack" and "reach" you should know, with precision, what it is i'm referring to. not some nebulous idea of height or length but, specifically, what these terms mean.

2. you should understand what i mean by "fit coordinate." you should be able to list the important fit coordinates, that is to say, you should be able to tell me what they are and, even better, you should have measured and written down what your fit coordinates are on your own bike. even if it's a bike that you suspect doesn't fit you well, it still exhibits fit coordinates - they're just the fit coordinates of an ill-fitting bike.

3. you should understand the rationale behind a properly designed and constructed fit bike. you should understand how a fit bike gets you from "fit coordinates" to "stack and reach" of a bike that might be offered for sale by a manufacturer.

if you have any problems with any of these three above, tell me what that trouble is, and let's fix it.

Dan Empfield
aka Slowman
Last edited by: Slowman: Dec 20, 10 8:59
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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Okay at this point I'm just embarrassed to ask, but I want to graduate.

When you say "fit coordinate" and be able to list them, I get confused. Are we talking about body measurements by themselves or with components, i.e., stem, bars, cranks? Sorry.

-J



Jehovah and family unity above all.
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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Well, since you asked about fixing, how about fixing the year-old bug in the profile setting for bike coordinates?

It's posted on the Development Forun from last January and does not allow numbers to be placed into the software you've designed. The error message reads "Are you sure all values are in mm and not cm?"

After you respond affirmatively, it returns the message "All values must be in mm."

I'd just like to get to grade school and record my data. I finally measured yesterday, using a drywall T-square and 2 levels I had in storage.

DFL > DNF > DNS
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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I've got the same question as VelocityDriven. I am guessing that it would be a series of measurements such as seat height, cockpit length (seat to pads vs. seat to bar tips vs. both?), drop from saddle to aerobar pads etc. It would be great if you could list them all out with any suggested conventions for measurement. For example with the bar drop, I would guess you measure from top of saddle nose to elbow pads? Ongoing thanks for your help. Bill
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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further with respect to fit coordinates, are those of us who do not have a bike (whether ill fitting or not) and do not have a properly certified fitter (or one who has the proper tools/instruments) or, worse yet, has both, but from past experience and reputation, does not exhibit close to the passion/caring that you do about fitting generally (or customers), doomed to not graduate, and spend our days in shop class, or Home Ec?

2 bikes I'm looking at would be the speed concept and transition - likely in XL size. Given the S/R of 44.5 and 56.5 (Trek) and 42.1 and 54.2 (Trans), would I expect these to "fit" the same with a 2 cm stem adjustment and a 2cm spacer height adjustment. Would that be correct? Would that imply that, at those sizes, the transition is shorter and lower? Perhaps the XXL transition is a better comparison frame at 554 450.
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Re: FIST 301: Are you ready for grad school? [VelocityDriven] [ In reply to ]
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regardless what the geometry of a bike is, there is a specific way you fit aboard that bike. there are certain places you contact that bike. for example, the saddle height is a "fit coordinate." if you have two bikes, and one has a seat post that's 54cm in length, and another's seat post is 56cm in length, one of these bikes is just going to have more seat post sticking out in order to get it to correspond with your saddle height, right? now, if i measure from the center of the bb straight up to the top of my saddle, midway between that saddle's nose and its tail, that measure is about 78.5cm (on my tri bike). that's a fit coordinate.

my saddle sits (on my tri bike) with its nose about even with the bb. that's a fit coordinate. it describes how i fit aboard my bike. again, that fit coordinate exists irrespective of the bike's geometry. if one bike has a seat angle of 77°, and another has a seat angle of 80°, i'm going to have to move the saddle back slightly on the 80° frame; or forward a bit on the 77° frame; because what's important is that my saddle needs to be where i need it to be, both in its height, and in its fore/aft placement. that's non-negotiable for me.

it's just like a suit. if my inseam is 34", and i'm getting a new suit, and the pants come with a 35" inseam, i'm sorry, i'm not going to wear it like that just because that's how it comes from the factory. the suit pants are going to have to be taken up to match my inseam. likewise, if a bike comes with a 76° seat angle and i ride at 79.5°, you're going to have to put that saddle forward to 79.5° and if the saddle can't go that far forward, then, sorry, i can't ride that frame.

but, look, at a certain point, it becomes really tough to jury rig a frame to match your fit coordinates. if your saddle height is 79cm, and your armrest drop is 14cm, you're going to need a bike with a certain "stack" that makes it easy to get your aerobars positioned. if the stack is too low on a particular frame, you're going to need a bunch of headset spacers. if it's too tall, and you take all the spacers out, and you have a downward pointing stem, and you still can't get low enough, that's a problem also.

so, what's important to know is this:

1. your fit coordinates are like your suit coordinates. i'm a 42 long, 15" neck, 34" sleeves, 34" inseam, 32" waist (during a good year). if i buy an armani, or a brooks brothers, or a saville row, does that change my suit coordinates? no. likewise, if i buy a cervelo or a cannondale or a felt, my fit coordinates - where i sit aboard that bike, and where my saddle is relative to the bb, the cockpit distance, the armrest drop - that doesn't change. my fit coordinates are uniquely mine.

2. the bike's geometry ideally should be a good match for my fit coordinates. if it isn't, i'm going to have to strain to get the coordinates to work on that bike. if i buy a 44 regular sport coat, and my "fit coordinates" are 42 long, then the tailor is going to have a time getting that suit to fit me, right? likewise, if my fit coordinates are better suited for a cervelo than a scott, or a scott rather than a felt, or a felt rather than a giant, then, my wise and proper choice of bikes narrows.

3. based on the above, i think you can see that unless you know your suit coordinates it's hard to know what suit you're looking for, and if you don't know your fit coordinates (your PROPER fit coordinates) it's hard to know what bike you best buy next.

one more thing: if a "static" set of body measurements works when determining my suit size, then why not for my bike size? because you don't do the high hurdles for time wearing your business suit. if you did, then you'd need a "dynamic" fit when determining the suit you should wear. you'd need a way to know what sort of suit works for you during the process of high hurdling. because you have to RIDE the bike, not just sit there on a bike, the best process for fitting you to your bike is a dynamic process. for this reason, a lot of footwear stores have you run down the block, or on a treadmill, before you buy a shoe. you want to test ride a bike before you buy it, right? well, you'll want to "test ride" your fit before you determine that this fit is in fact the fit you want to live with, especially because i can't know your saddle height REALLY until i know whether you're a toe pointer or a heel dropper, and i can't know what seat angle you'll be best at until i try you out in a variety of seat angles.

does this help?

Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [SallyShortyPnts] [ In reply to ]
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there are values we don't allow to be input into the bike fit manager because we *think* you're putting in cms instead of mms. my guess is that you - short (ahem) of stature! - might have a fit coordinate that, while in mm, falls outside our range. if you can PM jordan with your fit coordinates and ask him whether we need to widen a specific range, i think that might do the trick. this is just my guess, mind you.

Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [Camel's Toe] [ In reply to ]
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first off, everybody has fit coordinates, just like everybody has suit coordinates. even if you have no suit, you have suit coordinates. you have a neck, ergo, you have a neck size. you have a head, ergo you have a hat size. even if you have no hat.

likewise, you have a proper saddle height, saddle set-back/set-forward, you have a proper distance from the saddle (nose) to the armrest (back); you have a proper distance from the saddle nose to the ends of the extensions (where the shifter's pivot is). your armrests are so many cms or mms below the top of your saddle, and i measure this by placing one end of a 24" level on the top of my saddle, angling it over one of my bike's armrests, and i have a little 15cm long ruler than i place on the top of my armrest. i measure up to the bottom of the level. that's armrest drop.

and that's it, folks! those are the relevant fit coordinates! there are some minor coordinates you might want to consider. for example, if you measure to the midpoint of your saddle (from the bb) and you measure 4cm behind the nose of your saddle, you now have two "saddle heights" and the value of this is that you now have a measure of your saddle tilt as well. you might want to measure the distance between your armrests.

if you look at your forum user profile, you'll see a thing called "bike fit manager". if you visit my user profile, or rappstar's, you'll see our bikes listed, with our fit coordinates listed.

now, getting GOOD fit coordinates is the rub. which fitter do you trust? how do you know whether you're on the right track? subject for another lesson upcoming. first, i want to make sure you understand the three points above, in my initial post in this thread, and understand them thoroughly and unequivocally.

Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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If I'm understanding this correctly. This picture helped me visualize it.




You go in to get fit. The only items that move during the fitting are the items in blue - the seat and the aero bar.

The origin of the coordinate system is the bottom bracket. it is fixed. it does not move.

During the fit, you move the seat ( up,down, left or right) and move the aerobar (up down left or right ) until you get the perfect fit.

Once this is done, you take measurement A, B, C, D, E, F and G.

Once you have those coordinates, you look for a frame (using stack, reach, seat angle etc.) that allows you to most easily mount the seat and the aerobars in the exact points in space relative to the BB.

Is any of this incorrect?
Last edited by: elpete: Dec 9, 10 10:32
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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In Reply To:
at this point, what you should understand is as follows:

1. when i talk about "stack" and "reach" you should know, with precision, what it is i'm referring to. not some nebulous idea of height or length but, specifically, what these terms mean.

2. you should understand what i mean by "fit coordinate." you should be able to list the important fit coordinates, that is to say, you should be able to tell me what they are and, even better, you should have measured and written down what your fit coordinates are on your own bike. even if it's a bike that you suspect doesn't fit you well, it still exhibits fit coordinates - they're just the fit coordinates of an ill-fitting bike.

3. you should understand the rationale behind a properly designed and constructed fit bike. you should understand how a fit bike gets you from "fit coordinates" to "stack and reach" of a bike that might be offered for sale by a manufacturer.

if you have any problems with any of these three above, tell me what that trouble is, and let's fix it.

I have a couple of quick constructive comments about the curricula, and it's order of presentation:

  • It might "flow" better in the presentation and for the student's understanding if the explanation of "fit coordinates" and how they are determined and measured are presented prior to the discussion of frame stack and reach. I say this because in the process of either determining a particular bike size or other equipment, the fit coordinates are the starting point, or the inputs. The output can then be either the required frame stack and reach (i.e. choose frame size based on the chosen other equipment) or the other equipment required (i.e. stem and bars) based on a chosen frame, as you've described in your P3C and Slice examples.
  • I know we've discussed this in the past, but I still think that "fit coordinates" should use the same frame of reference (i.e. vertical and horizontal measurements from the BB center) as the frame coordinates. This tends to make things clearer from a conceptual standpoint as well...as in how fit coordinates "map" onto frames.


http://bikeblather.blogspot.com/
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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So this all makes sense and I find your descriptions very thorough. My main questions is, because I'm a perfectionist when it comes to these sorts of things) regarding optimization. I have a good fit on my bike such that im not particularly uncomfortable and I'm also feel fast, but I have a feeling that it could be better. How does one determine if their position is optimal? A computrainer or some other device?

Cheers


Michael J. Pelechaty
Brewer, Black Box Brewing Co.

"Yeah, I was depressed for a little while, but then I remembered how awesome I am."
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Re: FIST 301: Are you ready for grad school? [elpete] [ In reply to ]
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"The only items that move during the fitting are the items in blue"

bingo. you understand perfectly. once you go thru that process of determining your fit coordinates, then you're ready to start considering what bikes best match those coordinates. we have a system that matches bikes to fit coordinates. however! if you start with a bad set of fit coordinates, you'll get a faithful match using our system to that bad fit.

so, if a tailor measures you out to be a 44 regular, when in fact our true size is 42 long, then, a suit maker might provide you with a 44 regular faithfully designed to fit a person of that size. but if you're really a 42 long, then the process of matching your "size" to a suit of that size worked perfectly. still, you're in an ill-fitting suit.

so, it's important to know what fit coordinates are, and why they matter. second, however, is the harder task: getting your fit coordinates correct.

a proper fit bike will do two things: it'll be designed to grant adjustability, and adjustability along each important axis, to aid a fitter in easily, quickly determining where your saddle and aerobars should be relative to the bottom bracket. then, second, it'll be able to translate those coordinates to bikes that are for sale. alternatively, those coordinates can be translated to the geometry of a bike that a guru, or an elite, might build for you custom. that, by the way, is also a part of our system, and resides on slowtwitch, and in a future installment i'll show you where.


Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [Tom A.] [ In reply to ]
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"It might "flow" better in the presentation and for the student's understanding if the explanation of "fit coordinates" and how they are determined and measured are presented prior to the discussion of frame stack and reach."

i do as you suggest right now. in my workshops. and in our already-published articles in the bike fit section of slowtwitch. i'm trying a different approach, to see if this works any better.

"
I still think that "fit coordinates" should use the same frame of reference"

i do to, theoretically. and i would, if this was all on paper. that's why stack and reach use that same sole reference point. but certain things don't, in practice, lend themselves well to what seems intuitive. for example, saddle height might be best represented as an XY dimension. but it's hard to do that in practice. much easier to take the angular dimension.

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.

for example, if lengthening the cockpit creates discomfort, it's not because the armrests are further in front of the bb, rather because they're further in front of the saddle. this, because if you move the saddle and armrests further forward in tandem, pain in the back or the shoulder largely or entirely disappears. the relevance is not in the front end's placement v the bb, rather its placement v the saddle.

for these two reasons, i'm stickin' wit what i got.


Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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Hi Dan,

Firstly, thanks for sharing your knowledge on bike fit. I think I understand stack and reach, and I think I understand fit coordinates. I understand how to measure these on my existing bike/s. What I wanted to clarify is this: in order to get your stack and reach, and your fit coordinates, you need a bike which is a very good fit through a process of experimenting. Having tweaked your existing bike and found a comfortable enough position within the limits of what that frame will allow, without a fit bike etc, you may not be able to experiment enough to get your bike to the point of REALLY finding your best position? So the key again is finding someone who is worth their salt as a fitter or having to spend a lot of money on a fit bike or several bikes and parts? Hope this doesn't sound negative as I really appreciate you trying to drum all this into my thick skull!!! :)

Thanks,

Will
Proper fit coordinates.
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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Dan, thanks a million for taking on all the questions. I've long been a user of the stuff in the fit portions of the website.
Here's a quick one about the +/- conventions in the bike profiles on this site. I'm looking specifically at the three bikes in your profile.
For "B:plumb line, saddle nose to BB", when you prefix a "+", I gather that means your nose is ahead of your BB, and a "-" indicates behind (as on your Davo.)

Similarly, it must be that E:Armrest drop gets a "-" when then armrests are lower than the seat.
But on the road bikes, does "I:Handlebar drop" work the opposite way? You show a 75 there. Based on Ves' nice post of that bike's drawings in the 201 thread (and my assumption that you don't ride like my grandma), it seems you must mean 75 lower as well. I thought it might just be an oversight, but Jordan does it the same way.
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Re: FIST 301: Are you ready for grad school? [elpete] [ In reply to ]
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In Reply To:
If I'm understanding this correctly. This picture helped me visualize it.




You go in to get fit. The only items that move during the fitting are the items in blue - the seat and the aero bar.

The origin of the coordinate system is the bottom bracket. it is fixed. it does not move.

During the fit, you move the seat ( up,down, left or right) and move the aerobar (up down left or right ) until you get the perfect fit.

Once this is done, you take measurement A, B, C, D, E, F and G.

Once you have those coordinates, you look for a frame (using stack, reach, seat angle etc.) that allows you to most easily mount the seat and the aerobars in the exact points in space relative to the BB.

Is any of this incorrect?

Maybe I am not ready for this master's level course, but doesn't crank arm length have an impact on seat height and therefore fit coordinates?
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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I include this thinking it may be the right time in the conversation, hopefully to add practical illustration of the principle.

These are my fit coordinates from my curent bike, a 56cm Airfoil Pro. As built from the factory it does not fit me well, but through trial and error (4 stems, 2 aerobar combos) I think it does fit me well now. I have been professionally fit twice on it, once by a FIST fitter. As a disclaimer it was a lust purchase in 05 before I found S/R, I would not buy a long low bike now (I don't think).

Stack (Horizontal line from BB center)

BB to Headset Top center 510
BB to Stem Top center 590
BB to Aero Pad Top 650

Reach (Vertical line from BB)
BB to Headset center 450
BB to Stem Top (center) 420
BB to back of Bar 560
BB to back of Pad 510

Other measurements
Seat clamp to stem top center 550
Seat clamp to back of bar 640
BB to seat clamp (direct line) 720

I realize that I am missing a few things here - bb to saddle top, reach to bar end shifters. Also these are tape measure type measurements so may be off a cm or so.


So, realizing that I am riding with wayyy to many spacers, and feeling that my current bike is a little too long for me, I started my search for the next bike. I will likely recycle my front end (syntace CX bar/C2 extensions) which is average tall stack.

So I am looking at the following bikes thinking they might be candidates. (S/R from the table on ST)


Orbea Ordu 57 530 422

Trek Speed Concept L 541 426
Argon 18 E114/112 L 536 428
Trek Equinox 7 56 544 420

But I really like these other bikes as well:
Kestrel 4000 55 536 418

Scott Plasma L 548 416

I would buy the K4k all else equal. Will it fit well with my coordinates as above? Is it too short? Too long? What is the allowable range of "fudge" for stack and reach?

Thanks!
Last edited by: aztriguy: Dec 9, 10 14:06
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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Yes! Ready!

I believe my position is pretty good and rather powerful. It is not the most agressive, but I think better than it looks due to relatively short humerous bones. So, given that, I would like commentary of which high end frame work best with my coordinates. Perhaps that is "401."

Here are my coordinates:
A: Saddle height 738
B: Plumb line, saddle nose to BB +26
C: Cockpit (nose to extension tip) 760
D: Armrests to extension tip 350
E: Armrests drop -100
F: Saddle nose to armrest back 425
G: Armrest width 235

Many thanks,

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.
Last edited by: david: Dec 9, 10 14:01
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Re: FIST 301: Are you ready for grad school? [Slowman] [ In reply to ]
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Dan, What a great explanation. I have a much better understanding of fit coordinates and how they play a key role to come up with r&s. Truthfully, it was getting a little hard to comprehend, but as it's been said on here "a picture is worth a thousand words" Your explanation, the diagram posted here by elpete and by actually visiting your profile and seeing how many fit coordinates there are:

A: Saddle height B: Plumb line, saddle nose to BB C: Cockpit (nose to extension tip) D: Armrests to extension tip E: Armrests drop F: Saddle nose to armrest back G: Armrest width

Brought all the pieces of the puzzle together. I now feel comfortable enough to walk into any bike shop and speak to the fitter on a level where I can understand......thank you. Heck, as a matter of fact, if the fitter can't come up with s&r based on my fit coordinates, cause he feels he doesn't need one or two of these measurements......don't walk out of there, RUN!.

Now my questions change some. Moving forward. Let's say I now have all my fit coordinates, know the stack and reach of the frame needed. Find one, build one. I'm aero and comfortable to the point I can ride it miles on end. That's all fine and dandy, but is there a general rule of thumb to come up with maximum power output without compromising the first two? I don't have the gift of gab and typically can't explain myself well, but I hope you understand what I'm getting at here. Basically, I want to go fast without compromising aero+comfort. Would the rule of thumb here be to sit right over the BB, behind it or in front of it? Thanks again, thanks a mil.

respectfully,

-J



Jehovah and family unity above all.
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Re: FIST 301: Are you ready for grad school? [Barlow] [ In reply to ]
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generating your fit coordinates: there are a few ways to do this.

first, get yourself aboard a fit bike and experiment until you have it nailed. either with or without a fitter to help. the only magic about a fit bike is you can explore endless positions and you can do so quickly, and change from one parameter to another to get more or less instant feedback.

second, you experiment with your current bike, assuming that bike is not entirely out of the ballpark for you, and if you're willing to invest in a few stems, and if you have a frame and/or aerobar that is adjustable enough.

i would guess that most of the pro athletes over the past 10 years haven't had access to a fit bike, yet they've found a way to divine their own best positions.

all that established, nowadays there are some pretty neat fit bikes, and one of these good fit bikes in the hands of somebody who really understands what's going on is going to make it a lot easier. if you pay attention to this series of threads, you'll be able to tell which fitters understand the concepts, and which fitters aren't quite ready yet for prime time.

Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [tri_philly] [ In reply to ]
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"when you prefix a "+", I gather that means your nose is ahead of your BB, and a "-" indicates behind"

yes

"
drop gets a "-" when then armrests are lower than the seat."

yes

"
does "I:Handlebar drop" work the opposite way?"

it shouldn't. i'll take a look. my h'bar on my road bike is definitely lower than the saddle.


Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [y-o-y] [ In reply to ]
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"doesn't crank arm length have an impact on seat height and therefore fit coordinates?"

yes, it certainly does. when you change crank length, seat height changes, and armrest drop may also change.


Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [aztriguy] [ In reply to ]
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all those metrics you list are great, but they aren't the metrics i use, and are therefore not metrics i'm familiar with. i'm not a lazy guy entirely, but i'm certainly too lazy to try to derive my metrics from yours. so, you have to give me your fit coordinates according to the metrics i use before i can comment.

Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [david] [ In reply to ]
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how tall are you?

Dan Empfield
aka Slowman
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Re: FIST 301: Are you ready for grad school? [VelocityDriven] [ In reply to ]
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"if the fitter can't come up with s&r based on my fit coordinates, cause he feels he doesn't need one or two of these measurements......don't walk out of there, RUN!."

;-)

as to your question, that's a few classes ahead.


Dan Empfield
aka Slowman
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