The Prophet goes by the numbers.

Three Points in Space

Three Points in Space

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Most great ideas in life are accompanied by an unforeseen consequence of equal or greater magnitude. For instance, no one predicted that the Industrial Revolution would pollute our air and set off climate change on a global scale. Similarly, no one realized that when placing unfathomable computing power in the palm of our hands in the form of smart phones, it would gridlock traffic as people sit idle at green lights while updating their Facebook statuses. But most of all, no one anticipated that the invention of the Internet would reveal an entire population of people who can judge the quality of a rider’s position simply by looking at a photograph of the bicycle itself. That’s quite a Carnacian talent, one that might have saved the great Eddy Merckx quite a bit of time and hassle.

Legions of people have tried their hand at methodizing bike fitting for the obvious reason that it is theoretically possible and sounds nice and tidy. The problem is that we don’t understand the alchemy of biomechanics, aerodynamics, and physiology that determines the rider’s optimal position. As it stands, bike fitting is more art than it is science where experimentation informed by performance is the only way to get things perfect.

Eddy Merckx was famous for being relentlessly obsessive about his position. A Sunday in Hell and La Course en Tete both show him at work setting up his bikes; measuring the angle of his saddle with a spirit level and basing the height of his saddle and bars from the top tube instead of the more customary measure from the bottom bracket.

In contrast, Sean Kelly was known for giving his frame builders one measurement only: the height from the center of the front axle to the center of his handlebar stem; he felt that so long as he could get his bars at the right height, he could work out all the other dimensions as well. I used this method for years, until I realized that changing the bottom bracket height changes this measurement directly; every centimeter in bottom bracket height dropped increases the effective height of the bars by the same amount.

The fact is, our position is determined by the three points in space by which we are connected to our machine: the bars, the saddle, and the pedals. The frame, stem, cranks, and seatpost are just a means of holding them at the precise coordinates we determine for them. Replicating a position precisely from bike to bike is a challenge that I have yet to meet; I have gotten close, but I have never gotten it perfect.

The critical distances are the saddle height, bar drop, the reach to the handlebars, and the distance the saddle sits behind the bottom bracket (setback). To get my position as close as possible between machines, I standardize all my contact points; I use the same saddle, bars, and crank length on all my bikes which lets me eliminate those variables from the equation. Standardizing on a saddle, for instance, allows me to measure the saddle height from the bottom bracket to the center of the saddle rail which is less error-prone than measuring to the top of the saddle. Then I measure saddle setback using a plumb line and drawing marks on the floor to indicated where the bottom bracket sits and where the tip of the saddle is (the distance between them is the setback.) Then I measure the vertical height of the saddle to the ground and measure the height of the handlebars to the ground; the difference between these two numbers is the bar drop irrespective of bottom bracket height. (If you know the difference in BB height you can also add/subtract that difference from the axle-bar measurement.) Finally, I measure the distance from the tip of the saddle to the center of the bars.

In order to replicate this on another frame, I start with the saddle height, then setback, iterating between the two as you zero in on the correct measurement (sliding the saddle fore and aft will affect its height slightly; raising and lowering the saddle will affect the setback). Then I set the bar height, and then reach, also iterating on these two as the rise of the stem will mean you lose bar drop as you increase or decrease the length of the stem.

It all takes time, and unless you are using identical frames, you’ll never get it completely right. But you can get close. Also, you can consider the approach of caring whether your position is the same on all your bikes or not. I have friends for whom this works and who even enjoy having different positions on different bikes. They claim it lets them appreciate the different personalities of their various bikes. This approach is obviously completely incompatible with my personality type but does, on the surface of it, appear to be quite a lot easier than my approach.

// Accessories and Gear // Etiquette // Folklore // Nostalgia // Technology // Tradition

  1. Excellent piece! With all the various geometries of frames these days and an adherence to N+1 means getting things very close is about the best you can hope for. I use same saddle and bars on three of my five road machines. Crank length is the same too. Even with things close to within 5mm or so (mostly on bar drop) the various personalities of the different machines is still apparent. With new style stems, getting the each, bar height is much easier than in the day of quill stems, that’s for sure.

    I still check the mmeasurements every once in a while just to make sure they haven’t changed . . . .

  2. I’ve come to my position by years of trial and error. I can ride for hours with no pain in my back and knees and only after 3 to 4 hours some stiffness in my neck but that’s just ageing. In a couple of weeks time I’ll undergo a full Retul bike fit and all that entails with led markers/ sensors and The Zin. The fit was a gift, I wouldn’t have paid to change something I don’t think is broken.

    I don’t think my position is bad but I’m now very interested to find out if it could be better and why the technology says that. This fit will be only for the #1 as the fixed/ CX/ track and MTB are different beasts although the track and fixed are likely to be pretty close using similar measuring methods to Frank’s, perhaps slightly less OCD? Maybe not. I’m also part way through BC’s Head Physiotherapist Phil Burt’s Bike Fit book. It’s an interesting read and so far is backing up my own bike fit. It’s worth getting just to check out latest thinking and BC’s work on the subject.

  3. Here is a good tip for measuring saddle setback.

    push back wheel so it sits flush against a straight wall.

    measure level from wall to your chosen reference point on saddle, I go for the tip

    measure level from wall to centre of bottom bracket

    take awat the difference, voila your saddle setback and not a marker pen or annoying plumb line in sight.

    So easy and accurate, just make sure the wall is straight if using different walls.

  4. Ah fitters and their gadgets. I have had three fits over the years. They have varied by 2 cm in saddle height and 1.5 cm in fore/aft; Never mind the guy who convinced me my pedals were too close together and stuck me on the oddest one off pedal system ever seen.

    Needless to say I am now convinced that Merckx was correct here as in so much else; get a torque wrench, a tapemeasure,a level and a notebook and do the work yourself!

  5. Methodized bike fitting has been defined. It’s Cycling Analysis. It’s Cyclologic. Cyclologic.com for the curious. We have done what you seem to promote as unattained (alchemy?? huh?). However, you are correct in understanding that it is both art and science and it probably always will be. Yet, even with the accuracy of analytical tools, to find a proper fit requires a Cycling Analyst (bike fitter) with an intuitive understanding of biomechanics, and cyclists’ individual anomalies is paramount. Considering the outrageous amount of time a cyclists spend in a relatively static position on the bike, millimeters matter in the long run. It is millimeters of error that cause pain and saddle sores and discomfort. It is centimeters of error that cause malaise, back pain, and rapid burnout. With tools like pressure mapping and high speed resistance based motion capture, these asymmetries of the human body can be identified compensated for through correct frame size and accurate fit. But it would be foolhardy to think that the simple title of “bike fitter” alone is licsense enough to solve these kinds of problems just the the term “bike mechanic” does not qualify all who work on bikes to touch Campagnolo, ESP, Di2 or carbon. Training and – again – and inherent passion to understand the complex nature of cycling biomechanics is requisite. As spammy as it is to say it, Cyclologic has attained this and we see Cyclists of all levels travel to us because they know our abilities are Hors Categorie du Alchemy.

  6. I was blessed with a freshly printed copy of LeMan’s book as a pedalwan and set my position up using his paraphrased genius. Since then (save for a tendancy to move my handlebars lower over the past decade) my position has remained steadfast enough for me to set up a new bike sans measuring tape just by riding it a bit and making the occasional adjustment. They all end up with identical set ups.

    Its the one area of my life where a pathological sense of anal-retentiveness has not directed my behavior like, eh-hem, some of the others here.

  7. @pneaumme Was going to bring up high-tech fitting methodologies to get a feel for what others thought. I’ve always done iterative ways of dialing in my fit, i.e. drop the handlebars by a spacer, go ride. Feel OK? Drop another spacer. Too low? Put it back on. Etc etc etc. It seems to work reasonably well, but I’m a biologist not a physiologist, so it might be nice to bring some biomechanics and actual quantification to bear on the problem. It would be, as they say, sexie.

  8. Just bought a new seat clamp after raising the saddle a couple of mm’s and going ‘two turns passed stripped, then back it of half a turn’ to tighten the clamp. Feel the need to go a bit higher again. Tip – if you’re going to Eddy Merckx about your position, get a torque wrench!

    Here’s another headwreck thought when setting postitions on your muliple steeds, or with multiple shoes – cleat position on the shoe.

  9. Some folks are sensitive to mm changes, some are not. I for one, am not.

    After buying a new bike and setting it to match the old one I rode it for a a few months. Position fine. I then decided to drop the 5mm spacer out from under the stem that wasn’t there on the old one… I’ve been riding it like that for many many months. To me the position feels the same….

  10. @Simmo

    Here is a good tip for measuring saddle setback.

    push back wheel so it sits flush against a straight wall.

    measure level from wall to your chosen reference point on saddle, I go for the tip

    measure level from wall to centre of bottom bracket

    take awat the difference, voila your saddle setback and not a marker pen or annoying plumb line in sight.

    So easy and accurate, just make sure the wall is straight if using different walls.

    That is good! Do you use a long level to get the horizontal? And so long as the wall isn’t too wonkey or as you say you use the same one, everyone is happy.

    The plumb line is a it of a hassle. I’ve designed a contraption in my head that would work as a gig but it’s never going to be built.

  11. @beatarmy

    Ah fitters and their gadgets. I have had three fits over the years. They have varied by 2 cm in saddle height and 1.5 cm in fore/aft; Never mind the guy who convinced me my pedals were too close together and stuck me on the oddest one off pedal system ever seen.

    Needless to say I am now convinced that Merckx was correct here as in so much else; get a torque wrench, a tapemeasure,a level and a notebook and do the work yourself!

    Totally agree, just tweak until you’re happy and ten tweak some more until you’re not. Then go back. When you go mo’fasta the posish is right.

    Amazes me the eye for fit a guy like Guimmard had – all his riders looked just perfect. LeMond, Hinault, and Fignon being the best of his disciples.

  12. Eddy Merckx though was possibly obsessive about it because of back pain after his track crash in 1969, and, furthermore, is reported to have adjusted key dimensions during rides in order to relieve back pain, rather than in an effort to get the one perfect setting. Chris Sidwells in ‘A Race for Madmen’ quotes him as follows: ‘I started taking an allen key with me on every ride. At first I thought my pain might be due to a slightly incorrect position on my bike, so I changed the saddle height slightly, but the pain came back. I experimented some more and every time I changed the saddle, or the height or angle of the handlebars, the pain eased for a while’.

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