Height:
A basic, static, function to determine saddle height is with a book between your legs, feet 6” apart. Measure in centimeters, from the floor to the top of the book. Multiply this number by 88.3, and you have a GENERAL idea where to start (Lemond Method).
DO NOT RELY ON EXCLUSIVELY ON THIS DATA FOR OPTIMAL SADDLE HEIGHT! It is based on specific femur-tibia ratios and ankling protocols that are NOT identical to those you were born with. Longer femurs tend towards a lower saddle, due to the primarily horizontal function of that bone. Longer tibias correlate with higher saddles, operating in a more vertical plane.
And to make matters more complex, I have seen active adjustments range from 15-40 degrees at the knee (terminal extension) without injury
There are many other on-line methods available, but none entirely accurate due to variable limb ratios, connective tissue, muscle mass, training schedule and temperature.
Barring Injury, I suggest altering saddle height slightly during rides (post-warm-up) to learn more about what is right for you. The proprioceptive feedback from your adjustments will provide far more accurate data than the standard goniometer.
What to do when you find your “magic” saddle height? Try to understand that it is really not that important. Why? Because our bodies are dynamic, not fixed, units. Our strength, flexibility and endurance vary through the course of a season/off-season, altering terminal extension as a function of muscle conditioning.
Here is an experiment to demonstrate my point:
Try bending forward, hands towards feet. Do it again. Feels slightly different, right? See how far your hands extend from day to day, and gauge how the back of your legs/low back feels in the process. ALWAYS different – guaranteed! How do I know? Because it is molecularly impossible to replicate a physiological experience.
Listen to your body and adjust your bike!
Longitudinal Balance – Fore/Aft Position:
Morphology, Femur, Foot and Hip Angle are the most important anatomical variables for longitudinal saddle positioning, barring a predetermined top-tube length
Morphology:
Conceptually, longitudinal alignment is like a seesaw. The tendency to balance is achieved with equal weight and proximity from the fulcrum (hinge).
To demonstrate this principle, place an object 3ft. in front of your feet on the floor. Try to pick it up with straight legs. Now try with bent legs. Moving your butt back balances the fulcrum, drawing mass from your upper body and toes to our lower body and heels.
Next time you ride your bike, tilt and tuck your hips to decrease and increase weight relative to the fulcrum. Notice what happens to the arms. Tucking decreases upper-trunk mass and effective length; tilting increases upper-trunk mass and effective length.
Femur Length:
A popular method to determine fore-aft saddle position is to drop a plumb-line from your knee cap and adjust so that it descends to the front of your pedal spindle, with crank is at 90 degrees (or parallel to the floor).
Unfortunately the knee to plumb distance increases forward when subject to steeper angles, increased differential, and larger feet.
These images share identical hip with very different horizontal knee positions.
For more information: The myth of K.O.P.S (knee over pedal spindle)”, by Keith Bontrager.
Foot:
A big foot can alter ankle and knee angles significantly. Increased knee flexion = Increased shearing.
Hip Angle:
The ideal hip angle is a function of range of motion, muscle recruitment and firing sequence. Many fitters feel that hip angle is a constant, regardless of discipline.
A shallow hip-angle can recruit unnecessary muscle activation, hip movement, and stroke patterns, including possible contact between femur and ilium. Having an overly relaxed hip angle creates a similar scenario (but for the latter condition) including, inappropriate psoas recruitment, gluteal firing problems (resultant), etc.
Tips:
Be sure to adjust saddle height, when making fore/aft adjustments. Moving the saddle aft, increases saddle to pedal distance; forward, reduces saddle to pedal distance.
Use caution with video and motion analysis determinants for ideal saddle position. These tools provide, more or less, accurate body angles, but should NOT be relied on for optimal angles!
Remember: Your body is much smarter than the person providing your fit! If you FEEL something wrong, you are probably right; if you THINK something is wrong, get a second opinion. Don’t settle for less than IDEAL!
Addendum: I have since learned of a truly accurate tool for finding your exact saddle-position. It is the CAD program designed by Tom Coleman, founder of Wobble-naught. He has designed an extremely accurate, comprehensive measurement protocol and software application that works.
