With too much choice comes confusion and paralysis, because there’s too much to know and learn in order to make an informed decision. In the world of bike fit choice is about to expand, and those not paying attention will awake one day to find the sheer number of options daunting, with the question of what bike fit system to patronize virtually unknowable.

When I’m done with this series, in a week or so, I’ll have thrown a net over 5 fit system owned by companies selling, in the aggregate, about $7 billion of product a year. Or I’ll fail trying. You will judge whether I’ve tamed the fit system beast.

May I name the companies with systems that I’ll be writing about individually?

Wednesday I’ll write about Shimano, which showed a classy fit bike last year, at the Eurobike trade show, and this year you’re going to see much more than just a fit bike from this $2.5 billion company – including some technology you’re not going to find anywhere else.

Then there’s Trek and we’ll be writing about this fit program as well. You may think you know about Trek’s fit program. You don’t. (Unless you work at Trek, or unless you are a retailer who just returned from Trek World.) This is a completely new program, new from the ground up and, finally, a program that has its head screwed on straight.

The Guru system, owned by Cannondale Sports Unlimited, is about to announce enhancements to a well-funded, full speed ahead program accelerated by a year’s worth of steam.

Then of course there’s Retul and F.I.S.T. Here’s what seems to me to be the strategic difference: When it was just these latter two companies flogging their somewhat similar approach to bike fit, it was a pair of exceedingly small companies hollaring Jeremiads warning about the evils of ill-fitting bikes and unwise purchases. Since then, Specialized purchased Retul, so you now have Specialized, Shimano, Cannondale, Trek, all with their own fit systems. You could as well add Giant to that list. It’s got its own fit system – Ride Right – but it hasn’t launched in North American as of yet. This means the 5 largest bike companies worldwide all have their own fit systems with their own fit bikes and tools. Bike fit is no longer an arcane art practiced and promoted by eccentric propellerheads. Now it’s big business, and bike fit is more than just advocacy. It’s strategy.

But wait! How big can the fit business really be? That’s not the point. It’s what the door of fit opens into. Imagine a helmet fitting service. “I’ve measured the major and minor diameters of your head, calculated the bending moment of your ears, estimated strap dangle and, presto, you’re a... Giro! Or a Catlike. Or a Kask. Doesn’t matter. He who owns the system owns the output, and the output is powerful, because it’s not a salesman telling you what you should buy, it’s a scientific, customized to you, brand neutral analysis. Who can argue with that?

Am I suggesting that brands will cook the outputs to favor their product? No. But would you trust any one brand to run the entire industry’s metrics? Wind tunnel testing? Fatigue and stiffness testing? Rolling resistance? The Kona bike count? Whether you would or wouldn’t, the other bike companies wouldn’t, and that’s why they’re all coming out with fit systems of their own.

If you look at just the systems announced, or to be announced by the Interbike trade show in a couple of weeks, they are built on the same basic platform and, when I say this, I’m talking about how bikes are chosen. Saddles, helmets, shoes, I’m not talking about parts and accessory selection, just about bike selection. What is this platform?

**A Bit of History**

In 2003 we – here at Slowtwitch – began to take a fresh look at bike fit. Tri bike fit in the beginning, because that’s what we knew, and because that seemed to be a particular area of need.

When you sit yourself down and contemplate a fit system the typical, historical method is to measure and analyze a person’s morphology – his or her height, inseam, arm length, and perhaps range of motion or other limitations. You don’t need a fit bike for this. You need a tape measure. And maybe a goniometer (a kind of protractor for the body, to measure angles a body makes when striking certain poses). If this is the kind of fit system you build, it has a particular limitation: A person’s fit is determined without the subject ever actually riding a bike.

Some people – I among them – believe that the closer to the actual riding experience a fit process is, the more likely that fit process is to “stick” out on the road, and the less likely a subject is to pull out his Allen wrench and place his bike in a position he prefers rather than in a position determined via the “static” fit system relying only on morphology.

If you’re going to build a fit system that takes into consideration how one actually rides a bike, then the subject must necessarily be sitting on a saddle, aboard a bike, during a fit session. What it has taken several years for fitters, scratching their heads, to finally determine, is that it’s very hard to make changes to a person’s bike position, aboard a bike, during a fit session, unless that bike’s contact points – saddle and handlebars – are very quickly changeable up and down, back and forth. In other words, if you’re a bike fitter in a bike shop or a fit studio you can complain, scream, argue, reason, throw a tantrum, curse or pray but, eventually you’ll have to invest in a fit bike of some sort if you are serious about dynamic bike fits.

Still, that left us with “Part 1” of a 2-part protocol. The F.I.S.T. system was born, but incomplete. By 2003, we had two things, the first of which was a protocol that generated a set of fit coordinates. But what bike or bikes did these coordinates fit? I knew that we could not move forward until we redefined how bikes were measured, so that we could, for fit purposes, compare bikes one to the next. We did not “invent” Stack and Reach any more than Euclid invented geometry. We simply identified what was already there: X and Y coordinates from the bottom bracket to the head tube top. The value of these metrics is that they are absolute determiners of a bike’s length and height, for fit purposes. These were the two things we had in place by 2003 and it’s as far as we’d gotten.

It took 3 or 4 more years to bring to fruition what we contemplated in our heads, which was a system for matching fit coordinates to complete bike solutions, as in, “Based on your bike position you’ll ride a Cannondale Slice, size 58cm, with a 100mm stem, -6° pitch, 20mm of headset top cap + spacers, or you’ll ride a Trek Speed Concept...”

Why did all this take years instead of months? Mainly it was the grunt work of getting bike makers to understand what Stack and Reach were; explain why we needed a new metric on geometry charts; convince them of it; and get them to give me Stack and Reach for every size of every bike. That, along with prototype after prototype of fit bike, so that we would finally have a tool that matched, in functionality, precision and sophistication, the protocol.

Even then, we weren’t done. I am not the brightest guy. Worse, I am not always the most observant guy; the shrewdest guy; and best strategist; or the observer of the obvious. It took another year or two for me to recognize the next, obvious, painfully obvious, truth. I had solved a truly difficult problem: complete tri bike solutions. The comparatively easy step of road bike fit along with complete bike solutions I skipped right over. Why I did not realize that sooner is God’s own mystery. It took just a few weeks to whip up a protocol and system for road bike fit.

**Serotta**

We at F.I.S.T., and I in particular, did not invent the notion of fit bikes, of dynamic fitting, and of X/Y bike coordinates. Dynamic fitting has been around for years, and the method pretty much all of us use nowadays for saddle height is, or is based on, the Holmes-Pruitt method, described in the literature as early as 1994, Pruitt being the Andy Pruitt of bike fitting fame and of the Boulder Center for Sports Medicine. The method itself assumes a dynamic fit process.

But the true innovators and pioneers were, I think, the folks at Serotta. Its fit bike, and its accompanying X/Y tool, did output the X and Y coordinates from the bottom bracket to the handlebar clamp. From there it’s simple (well, for some more than others) trigonometry to divine all the elements – frame geometry, stem length and pitch and so on – taking a person from fit coordinates to a complete bike solution. When it comes to “Part 2” of the fit system – translating fit coordinates to complete bike solutions – the chasm between Serotta's system and what we introduced in F.I.S.T. is not gaping. Whether that chasm was a chasm or a crevice or something in between is debatable. We identified and attaching primacy to the spatial relationship between the BB and the head tube top. We generated a sportwide database of these metrics, bike by bike. We formalized a system for matching fit coordinates to bikes already in manufacture, rather than building custom bikes to match these fit coordinates.

Mentioning Serotta’s groundbreaking work is important, I think, for 2 reasons. First, it’s important to give credit where credit is due. Second, this history is necessary to prove a thesis I’ll give voice to below: All these fit systems I’ll be writing about this week are built on a similar platform. If you said the system I built for matching fit coordinates to production bikes is little more than a production version of what Serotta was probably already doing for custom bikes, that’s a case one could make. In any event, that’s what the F.I.S.T. system is – at least the part where we match fit coordinates to complete bike solutions - and all these variant fit systems I’ll be writing about this week largely parallel the F.I.S.T. system (because there's only one way to do the math). While I didn't study the Serotta system prior to devising F.I.S.T., I don't know whether the F.I.S.T. system would have built as quickly or in the same way had Serotta not come along first, and I can't help but wonder what the Serotta system could have morphed into had it kept the pedal to the floor and continued to innovate and let that system lead Serotta to places the company never went.

If you followed what I wrote above, or even if you didn't, don't misunderstand. The difference between F.I.S.T. and Serotta is huge in how we identify your position (your saddle fore/aft, cockpit distance, handlebar elevation, etc.). The systems couldn't be more diametrically opposed to each other. Once we've identified your fit coordinates, turning those coordinates into a complete bike for you (whether custom or production) that's where I suspect Serotta's math and the math baked into the F.I.S.T. system are probably related.

It's these differences in protocol, during the first part of the bike fit process, i.e., establishing fit coordinates, that ought to cause both fitter and end user to think hard and choose wisely when settling on a fit system. Some differences in fit system protocol are profound, some not. When Mat Steinmetz – ex of Retul, but originally of Retul and really probably the best exemplar I know of the Retul protocol in execution – fits somebody for a tri bike, and I fit that same somebody for a tri bike, Mat’s fits and my fits seem to be eerily similar. So, I think we, as fitters, and in fit systems, are not on divergent paths; we’re on convergent paths. Still, there are notable protocol differences, road and tri, which I will explain as I describe each system individually later this week.

Second, some of these systems have specific parts and accessory modules. The F.I.S.T. system isn’t a system for prescribing saddles, helmets, shoes, or pedal/shoe interface. But other systems do, or will, prescribe parts and accessories (P&A).

And third, the tooling is very different. Tools – both fit bikes as well as motion or video capture systems – vary significantly in what they do.

Just, once you determine a set of fit coordinates, the actual math – the underlying process of getting from fit coordinates to complete bike solutions – is identical, and that’s because there’s only really one way I know of to get to a complete bike solution, and it’s the process I’ve described above.

**How these Systems Work**

What do we mean when we say X and Y, in the context of bike fit? Remember your high school geometry class, the Cartesian graphs and coordinate systems. You started at (0,0), and the X axis (horizontal) was some distance away from “center.” Maybe it was 5 inches away, or 5 feet or 5 yards or miles. But a point might also have some elevation to it, and that elevation is described as so many inches, feet or miles away in the Y axis. You could plot a point in space by saying it’s (5,3) and that’s 5 inches away from the starting point along the horizontal axis and 3 inches up in the air, vertically.

Stack and Reach are simply X and Y coordinates from the bottom bracket (0,0) to the head tube top (there's an image showing Stack and Reach on a bike above). You could look at the image furthest below and say that the shortest distance from the bottom bracket to the head tube top, in this pink right triangle, is along the hypotenuse. But the X and Y distance, along the long and short arm of this angle, describes Stack and Reach.

But how do we get to a “complete bike solution,” that also determines the length and pitch of the stem, and so forth. Well, if Stack and Reach are “big” X and Y, these horizontal and vertical distances could be said to make up “little” X and Y, which is the distance from the head tube top to the handlebar clamp.

Some fit bikes measure X and Y to the head tube top (Stack and Reach). Other fit bikes measure to the handlebar clamp. No problem, or to put it another way, it is a problem: a math problem. But that’s all it is. F.I.S.T. can work with either kind of fit bike, and as we get under the hood of these fit systems and fit bikes I’ll describe the benefits and the drawbacks of each kind of fit bike.

The point is this: Whether it’s the magical way that the Guru fit system spits out complete bike solutions down to stem length and pitch, whether it’s Retul’s Frame Finder, whether it’s the calculators and tables we have here on the Slowtwitch website, it all boils down to the solving of these two right triangle problems in the image furthest below: the red one and the green one. Now, that green right triangle, if you want to get really technical, that is actually a combination of two more right triangle problems that need to be solved, and these two are represented in the image just above. If you're a fitter, you don't have to worry about this. We have calculators for you, online. We have one that gets you from handlebar X/Y to frame X/Y (Stack and Reach). We have another that just calculates the X and Y dimensions from the head tube top to the handlebar clamp. If you never want to even worry about any of this, the Guru system, and Retul's Frame Finder, just do all this trigonometry for you. If the complete bike solution is an omelet, at F.I.S.T. we teach you how to cook the omelet. At Guru and Retul, you just sit down at a table and they serve you the omelet. But the way the omelet is made is identical.

You could go further, and perhaps make another triangle from the handlebar clamp back and up to the armrest pad. Maybe we add a blue triangle to the image at the bottom of the page. If you build a system that automatically calculates and spits out complete tri bike solutions based on the X and Y coordinates from the bottom bracket to the armrest, then you’re solving these three right triangle equations.

There is really only one way to do this math, and when you realize this you can begin to parse between the school and the protocol you like; versus the fit bike best able to execute your protocol; and if you want to use a motion or video capture system, which one of these you prefer (I’ll get into the use of motion capture, what it does, what it doesn’t do, later this week).

**The Consumer and the Fitter Face These Choices**

One way to look at these systems is that we hold a tremendous amount of our DNA in common. Looking at the fit systems above – for the purposes of bike fit and selection, not P&A selection – is like looking at all primates, or all canines. We’re all share a common general way of getting to the end result, and there is great consensus in what we believe and the mechanics of how fit operates. Maybe a better analogy is that we’re all Protestants, and it’s a question of preference: do you prefer Methodists, Lutherans, Baptists, Presbyterians?

How do you choose? And, really, this is a question not only for end users, even more so for the fitters and shop owners who must make a bigger financial decision that any end user will make, the decision not only having financial consequences, but will impact years into the future on questions of floor space, employee training, and the quality of the bike fit product the store delivers.

The very best advice I can give is this: I’m going to write about 5 fit bikes over the next few days. Regardless of what anyone tells you, these fit bikes operate essentially the same way. This does not mean that they all are equally good. Rather, that if you buy a Kia Sportage it’s going to get you from point A to point B. If you buy a Rolls Royce Phantom it’s also going to get you there. But there’s a big, big difference in the quality of the ride.

You can learn how to drive either of these cars in driver’s ed. You can also learn to drive at the Skip Barber Racing School.

If you are Retul-trained, you should be able to “drive” any of several fit bikes. If you are F.I.S.T.-trained, you certainly will be able to use any conforming fit bike. Fitters need to make an educational decision based on the tools they intend to use (don’t choose a fit school naïve to the Guru Fit Unit if you’re going to invest in a Guru Fit Unit), and based on the protocol the fitter is most confident in.

I do not mean to suggest that all fit bikes are usable for these newer dynamic protocols. If you buy a horse trailer and expect it to get you to your destination, the fact that it has 2 axles and 4 wheels isn’t enough. The bikes I’ll write about this week are all “conforming” fit bikes, that is, they all conform to these new protocols these major companies are introducing or have introduced. As for the other fit bikes, that’s not necessarily the case.