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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@beatarmy
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.
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'.
Like @Ccos I seem to have come to fitting early and easily. If memory serves when I started riding long races at 40kph position became something that got sorted pretty quickly. Now just getting on any bike and muscle memory can get me dialed in quickly.
The only thing that makes me think that I have it easy is that I am average height and do not have any kinks in back, legs, knees or feet. For those that do I can not imagine the hassle in getting set up. My adjustments go to the millimeter for cleats and within +\- 5mm for saddle height. Stem and set back are more forgiving and the change is enjoyable.
I have found that pedal float helps me find the sweet spot for cleats, meaning that on the new Looks if I get close then listen to my feet then I will be able to set them gradually to where my foot goes most. Of course Speed Play would negate all that.
On the saddle height spinning over 120 will make you bounce weather you are a little over or a little under your optimal height. Once adjusted, sometimes as little as 2-3 mm, up or down to find the sweet spot the bounce goes... assuming one has a good stroke! This works a treat on fixed and then transfer that height to the road bike and raise it a tad for more power.
@Owen
And that's exactly what the FIST fitting protocol is all about. You get on a fit bike - the fancy ones are even motorized and wireless - and pedal away. Fitter changes something until it's too much, than backs off until it's too little. Again and again, but a FIST fit will take an hour or three rather than several days - and you can "put your finger on it" much more easily if you can swap between two setups back and forth within seconds.
Completely agree with this. So much so that I'm tempted to make my next road machine one size down in frame size, while matching these three points equally to my current No 1 steed. This means building it myself, with proper crank length, bar width, stem etc.... Looking forward to the experience. (recently replaced all my componentry myself, so feeling much better about taking on such a task)
Yet despite it all it did not always work so precisely for The Prophet. I like the bit in a Sunday in Hell where he gets a spanner from another team car and gives the saddle a bit of a whack before tightening and setting off again. The benefits of a newspaper strike impromptu stop if I remember correctly.
@frank
Nice technique there! I have a contraption for measuring plumb line - a long (4' I think) level with a base on one end. Set up next to the BB and measure back to the saddle tip. It's also good for saddle/bar drop and saddle level too. I got a friend to make it up for me. So long as you work on the same area/floor when measuring different bikes, it's all good.
@Teocalli
I was thinking of the exact same scene. He borrowed the spanner from Brooklyn no less IIRC.
@wiscot I keep thinking a nice big drywall square would be just the thing for accurate setback measurement.
@Nate
I use that, and a 48" level lined with the center axis of the crank (level at the crank, drywall square to saddle). If the frame geometry varies between bikes, this way of measuring always puts my knee is the same position over my foot.