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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@frank - The lead pic could easily show up in an AOP article:-
Q: How many men does it take to find Eddy's saddle height?
Couple of things here. Part of the reason the Prophet was always fiddling with his position was as a result of his 1969 crash at the Blois velodrome where he fractured a vertebra and twisted his pelvis. He admitted that subsequently he often rode in pain and was never the same rider again. One can only imagine his career had he been fully fit!
His bike is getting the full measurement/adjustment protocol because His sideburns have already been treated to the same meticulous measuring and positioning. No stupid-looking beard here, just hirsuite awesomeness!
Yup, I'm in the tribe of not minding, and even enjoying, a slightly different set-up/position on all of my different bicycles. As your friend points out, it brings out different personalities. But, the bb-saddle height and reach is pretty darn close on all of my bikes, even my do-it-all commuter.
When I first got into road cycling I laughed at people discussing cms or even mms of difference. Over a decade in the saddle, I now know how easily you can tell your bike is off if a pillar has slipped or a buddy has played a joke and moved something.
And the distraction of phones. GREAT story for ya - down the block from where I live a college kid was robbed at...hammer-point. I'm absolutely positive they were texting and also wearing ear buds, so fucking distracted they let a strange dude wielding a hammer get that close to them without even looking up. I'm continually amazed at how distracted and addicted people are by their phones. Sure I'm not the only one, but I've seen two people out at a restaurant hardly interact with one another the entire meal, just head down, playing away. Bonkers.
@Ron When I first got into road cycling I laughed at people discussing cms or even mms of difference. Over a decade in the saddle, I now know how easily you can tell your bike is off if a pillar has slipped or a buddy has played a joke and moved something.
Whoa! We've had discussions here about the massive inappropriateness of just sitting on another guy's bike. Fucking around with moving things is beyond the pale. That is not funny, not now, not ever. That would be the act of an soon-to-be ex-buddy.
@wiscot
Hell, there's not a single hair on his head that's out of place!
So long as I am comfortable on my bikes I don't bother much with the minutiae of fitting. In addition, I doubt that Frank's methodology would be completely accurate: different frame geometry from bike to bike. A couple of degrees can make a noticeable difference based on my observations, but then again I am no expert.
@wiscot
This. That was apparently a really gruesome crash while in a motor-paced race. The derny driver died in the accident, Merckx had head trauma and the infamous back injury.*
Thanks to some archived articles on this site, I've been fiddling with my saddle and bar positions lately. I'm not exactly sure why, since I've been comfortable and low for years. I actually had some (self proclaimed?) bike fit guru say I would generate more power if I wasn't so low. I found that absurd, since I'm barely hitting the Rules compliant 4cm drop. Today's suffer-fest proved that experimentation can be good or not so good. Back pain all day, time to re-evaluate my changes.
*as cited in Eddy Merckx: The Greatest Cyclist of the 20th Century. Why is this not listed as required reading here?
@pneaumme
does your fitting program study a rider over the course of serious riding for half a season or more? If not, you are telling yourself convenient stories about how comprehensively you understand the system.
As a scientist and mathematician who flirted with physics, I agree the idea of defining this stuff comprehensively is awfully tempting.
@Ccos
I have bought a new copy recently which I love. That dude rules.
he espouses the virtues of riding the smallest frame possible and I've noticed since that his stem was always slammed. Stud.
@Puffy
I envy you but also am sad you don't get to experience the satisfaction of getting it right.