I originally wrote this article in May of 2013. I wrote it then because Slowtwitch forum members too often (justifiably) complained about bad results from bike fit sessions.
Forum threads of this type have continued in the 4 years since this article was first published, including a thread just published today inquiring about an upcoming fit session. Will it be a $250 well spent?
Let’s talk about what you should be getting out of a bike fit session. The last third of the article is devoted to what else you need from your fit session beyond what I listed in 2013. What constituted a thorough and professional set of deliverables back then no longer suffices now.
Below is any customer's reasonable expectation. It's the "output" of a fit session and at a minimum it's just 4 or 5 numbers that you need. I don’t believe this is just my idea of the output, or the F.I.S.T. protocol’s output, I think by now it’s recognized by Retul, Guru Experience and others as a consensus set of deliverables. The problem is that not enough of Retul’s trained fitters, Guru Experience trained fitters, or fitters I have trained in our own fit workshops, are providing these deliverables. What output am I talking about?
Saddle Height – obvious and simple. I measure from the bottom bracket straight up to the top of the saddle, halfway between the tip and the tail. Certain saddles I alter this convention, and an ISM Adamo is a case in point. There are only several centimeters of rideable “flat” on the saddle, near the nose, and I measure to the center of this section of rideable flat.
Saddle Fore/Aft – the nose of the saddle relative to the bottom bracket. This is strictly an X measurement, meaning if you consider your high school geometry, a Cartesian graph can be used to plot a point along the Y axis (height) or along the X axis (length). We’re just talking about where the nose of the saddle sits, in length, in front of or behind the BB. We also call this a “plumb line” measure, because if we drop a plumb bob from the nose of the saddle and we measure horizontally from the BB to that line, that’s our measure. With a road race bike set up with traditional road bars your saddle nose is going to be behind the BB, somewhere between 8 percent and 10 percent of your saddle height (so, if your saddle height is 72cm, your saddle setback will probably be between 8 and 10 percent of that amount, which is between 58mm and 72mm and trending toward dead in the center). The saddle on your tri bike will sit in an entirely different spot fore/aft. The saddle nose is going to be close to the BB, maybe a little behind, maybe even in front of the BB.
Cockpit – depends on whether it’s road or tri. Road, there are two measures I’m interested in: saddle nose forward to the center of the handlebar clamp; and saddle nose forward to what I call the “hood trough,” which is that depression in the hood right before that final upturn (look at the image above). I measure this in a straight line and I call this an “angular” measure rather than an “X/Y” measure. I’m simply measuring directly from the saddle nose to the center of the clamp where the handlebar passes through the stem; and again from the nose directly over to one of the hoods, to the trough. Make sure, obviously, that the wheel is pointing straight forward when you do this. Now, on a tri bike, it’s different. What I want to know is: saddle nose to the back of the armrest (first place that line can touch the armrest); and nose forward to the shifter pivot, which should be directly in line with the index knuckle (where my index finger attaches to my hand). Again, these are angular measures.
Handlebar elevation – now we’re back to X/Y measures. This is a Y measure. For road, it’s the elevation of the top of the saddle down to the handlebar, the top of the bar, right at that 31.8mm section as it’s ready to pass through the stem. I measure this by placing a level on the saddle, right about the saddle’s midpoint, and hold the level over the front of the bike, just barely to the side of the stem. Then, with the level horizontal, I measure from the bottom of the level to the top of the handlebar. Tri bikes, same sort of thing, just I angle the level over a little more and hold it over the armrest, and measure down to the top of the armrest. This is armrest elevation.
That’s it. these are fit coordinates. “Wait!” you complain. “What about saddle tilt, aerobar angle, the distance between the armrests!” Sure. Fine. Yes. But these are minor coordinates and don’t port into any system or calculator helping you determine what your complete bike solutions are.
Further, I’d be happy to talk about all of these other metrics, along with a discussion about where your pursuit bars should be on your tri bike, and where the drops and tops should be on your road bike. I’d like to talk about road bar geometries and how they affect your fit and ride quality while in various rider positions (climbing, riding in and out of the saddle, riding in the drops).
Here’s the problem. Too many fitters aren’t even giving you your basic fit coordinates. And without these coordinates you aren’t the master of your own bike.
Now, once you know these coordinates, what can you do with them? Plenty. I can tell you all sorts of things about your bike, your future bike, road and tri, and about whether those fit coordinates seem logical. If you complain to me about lower back pain I might be able to quasi-diagnose possible problems with your fit. But I need to know your fit coordinates, and we’ve made it pretty easy for you. For some years we’ve given you the ability to place your fit coordinates right on your forum user profile. At the bottom of the profile. Here’s mine.
Complete Bike Solutions
This is rougher, because it requires a knowledge and perhaps some tooling that not every fitter has. The stuff above, fit coordinates, a fit is of no value to you whatsoever if you don’t get these. Now, if you get these, well, it uncovers a fitter’s limitations as a practitioner if the coordinates just don’t make any sense whatsoever, so, I sort of understand why they aren’t given out by some fitters. Still, this is what you paid for.
Turning fit coordinates into complete bike solutions is kind of extra credit for your fitter and requires, in almost all cases, X and Y coordinates to one of two places. Depending on the fit bike (if used), or fit tooling, you’re either going to get X and Y from the bottom bracket to your “perfect” bike’s head tube top; or to that perfect bike’s handlebar clamp (where either a road bar, in a road fit, or the pursuit bar in a tri fit, pass through the stem). I can give you the bikes that match those fit coordinates if I have either set of X and Y coordinates.
Two kinds of popular fit bikes — the Retul Muve and the Exit Cycling fit bike — give you X/Y to the head tube top as an output. X/Y to the head tube top is another way of saying “Stack” and “Reach.” You can port these numbers straight into our stack and reach tables.
However, if you were fitted aboard a bike like this, you MUST know what length stem was used during the fit, what the pitch of the stem was, and if there were any spacers under the stem during the fit (and how high was the spacer).
If you were fitted aboard either a Purely Custom fit bike or a Guru Experience fit bike, these bikes don’t accept stems, so, there’s no need to note and archive the stem configuration used during the fit session. However, in all cases, and with all these fit bikes, you need to know:
Road Fit – Handlebar reach
Tri Fit – The model of aerobar used, the pad height aboard the centerline of the pursuit bar
This is minimum. It would also be nice to know the position of the center of the pad fore/aft of the pursuit bar.
Also, in all cases, it’s necessary to know what model of saddle used for the fit, and it would be nice to know what crank length was used.
This might seem like a lot, but it’s not. The fit coordinates above are essential for you, because you can’t set up any bike unless you know your fit coordinates. The other stuff — everything underneath the heading of “Complete Bike Solutions” — this is the list of complete bikes that will fit up under your fit coordinates. If one doesn't have the metrics listed above, it is not possible to "prescribe" with any precision what bikes will work for you. I can't do it, and nobody else can either.
However, if I do have the numbers above, I can tell what list of bikes will match your fit coordinates, or what the geometry needs to be of the custom bike getting built for you.
Under the first heading above — Fit Coordinates — you'll find the bare minimum that you should demand and require of your fitter. Under the second heading — Complete Bike Solutions — this represents the state of the art in bike fitting. A properly trained, experienced fitter will do this for you. It will require one of the four fit bikes named above, or a fit bike that does what these fit bikes do. If you talk to the folks at Guru Experience or at Retül they'll tell you that what I'm writing here is true and correct. What none of us really are comfortable telling you is that a number of the fitters all of us have trained haven't exactly gotten this memo.
In fact, print this article out and hand it to your fitter, and that will constitute the memo.
What has changed between 2013 and 2017?
Two updates to this. First, because of the move to fully integrated front ends on tri bikes, bike makers have had to fashion a work-around. The typical trigonometric equations that allow us to resolve a frame's stack and reach from handlebar X and Y do not work if the bike does not have a typical stem. The workaround is a solver or prescriber based on Pad X/Y. Did I lose you? Let's see if I can get you back.
Per the image above, if you tell me your X (horizontal) distance from the bottom bracket forward to the center of the armrest if your ideal position; and the vertical component as well; I can tell you exactly what Trek Speed Concept you'll fit aboard, with granular precision.
The "prescription" might be: Size L, low/far stem, 25mm pedestal, pads pushed forward 15mm from "neutral". If you give me that same set of metrics, except to the back of the armrests, I'll tell you which Quintana Roo PR6 you'll ride with the same precision; or which Giant Trinity Advanced Pro, or the Cervelo P5X. These three bikes use X and Y to the back of the pad. Here you'll see on a black background the solver for the Orbea Ordu OMP. You'll see a small red square there that identified my Pad X/Y position. As you see I can actually fit on 3 sizes of this bike, and then it becomes a handling and weight displacement decision. Where I am inside a size's parallelogram tells you how many pedestals I'll need under the armrest and whether I'm in the middle, or forward, or rearward of the bike's neutral position.
If my "dot" is way toward the front of the parallelogram, that bike is probably not long enough for me, if I want a really nice-fitting bike. If, after a tri bike fit session, you aren't getting a discussion from your fitter kind of like what you've read in this paragraph, that's a problem.
For this reason there are three new numbers you need from your fitter: Pad Y, pad X to the center of the pad, and pad X to the back of the pad. With these numbers you'll know which Diamondback Andean to buy, or which Felt IA, or the Scott Plasma, or the BMC TM01. All the modern tri bikes have solvers now.
The second new thing I think you need is a video. In fact, more than one. First you need to see the videos of the "artist's work". Today, I don't know that I'd even sit for a free bike fit session (let alone one that cost $250) unless I saw examples of the fitter's work. Above is the video of a Slowtwitcher who sat for a fit session, got the fit, and then posted the video of the fit on our forum asking whether our forum readers thought this was a proper fit. After much comment and hand wringing, this Slowtwitcher traveled down to the Los Angeles area and was repositioned by our head F.I.S.T. instructor Ian Murray. Below is the result.
If you think the above video is evidence of a fit you admire, go see that fitter. If you like the video below, go see that fitter and give him your money.
This got me thinking, and I had our CTO, Jordan Rapp, put a new field on our database of fitters. It's called Portfolio, and if you click our Search button the very first searchable option is every fitter who has a portfolio. I'm going to be a nag about this. I'm going to pester all the fitters on our database to find some way to show to prospects what the fitter's work looks like. The portfolio can be as easy as throwing up videos of fits on a Youtube channel and the portfolio link on our database listing refers to that channel. Mind, as of this writing this is new. It's going to take awhile for fitters to get this done.
Finally, I think you should have a video of your fit. I've just seen too many times when the subject wishes he'd had his fit memorialized in video.
A fit session isn't a discrete occurrence that happens, like a tonsillectomy, and it's immediately in the past, not to be referenced. It's more like a physiological test that generates a set of numbers that you use for training and racing. It's a tool that carries forward. And it's a tool that's yours, that you use.
All the protocols that rely on the use of dynamic fit bikes and resolve complete bike solutions using frame stack and reach began with, well, me. Since they are all progeny in one way or another of the F.I.S.T. protocol which began in 2003 I'll continue to prod them along, as they also apply gentle, welcome pressure to me.