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.
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View Comments
@Len
Yeah. We all have excuses for our obsession. Although I know this is true of Merckx to some degree. He'd also have his mech keep bars wrapped with different length stems to swap during races. But his obsession still points to one thing: a compulsive nature.
And who knows, maybe if he'd ridden a 20cm drop like I do his problems would have resolved themselves.
@Rob
Let me summarize: for those less awesome than @Rob, too fucking bad. He's awesome. You're not.
Everyone without a magnificent stroke can tune out. Everyone else, train on a fixie and go up a tad for Maximum Awesome.
@frank
True to my dual Dutch/Canadian nature, I fashioned a gig using a hockey stick, level, measuring tape, and, of course--duct tape. Cheap and works great, eh?
@wiscot
That's all very well, but what the f#*k has happened to the page with 'The Rules'? When I click on it now I just get a blank page with a message 'sorry, no posts matched your criteria'. I'm about to make public a blog on a ride a group of us are doing across Oz from West to East in which stict adherence to 'The Rules' is part of the discipline, but the link to it leads to sfa.
Help!
Spikey
@frank Yes. As well your tone of professional arrogance is Very Hors. We appreciate this.
We work continually with our clients throughout the season, pre & post. Our clients range from category cyclists, olympians, juniors. The list is of weight, I assure you.
Thank you for your excellence in trolling.
What I love about the lead picture is that it takes five people to get the Prophet's bike set up - I'm assuming Mr Trenchcoat in the back is handling the spare bike. This is an attention to detail that Sky can only look at in wonder and envy.
@pneaumme You're done now -- right ?? I for one need to figure positioning out on my own; change saddles on my decision; compare bars and drops as I want; go as far with stem length and angle as need be; alter crank arm length to feel for myself. And purposefully build different frame sizes to find it all over again. Methodized is always boring and not very meaningful.
I was a better climber on 172.5mm cranks but then became a better killer at 177.5mm. And finally to dispel my "unknowns" went to 175mm.
@wiscot " I'm assuming Mr Trenchcoat in the back is handling the spare bike."
Or stealing shit while no ones looking. It's like the crowd photos where the one dude not smiling is the one who's gonna shoot the president or something. How come he's squandering his opportunity to stare at the Prophet's bike with rapt attention like everyone else?
My 'technique' for this is to have a few bikes with different geometries and frame sizes, and have the utopian ideal of getting them all set up the same. I then use each ride as a sort of pairwise comparison, comparing the position of the current bike with the last one I rode. If I dislike something about the setup of the current bike, I change it. If I think something about the setup of the current bike is better than the previous one, then I go out on the previous one again for a quick spin and then maybe change something about that.
Done properly, this could keep me occupied with bike setup for at least one lifetime. But in reality, after several iterations, they're all pretty close, and I don't think I'm that sensitive to minor discrepancies anyway.
Being an engineer by education I have a fundamental desire to build a jig, but this would a) assume that one bike has an ideal setup, which is probably untrue, and b) deprive me of the dissatisfaction - rectification - satisfaction - and repeat cycle that seems dissatisfying but in reality is part of the fun.