Copyright
© 2002
Prepared by
Warren Cay
bikeNOW P/L
I believe this to be more important than seat height as long as your seat is too low not high. The most popular method in the world at the moment for seat aft position is the vertical line through the pedal spindle (knee method) explained below, however this occasionally just doesn't seem to get it right. Chris Salisbury who is one of my personal training masters and is one of our famous old school professional riders who is still very quick for a guy in his early 50's, can look at a rider and see what needs to be changed and always be right however can not quantify a method more than "I just know mate!" A big believer in "the computer can not replace the eye and feel angle" believes that the knee method below puts you in a too high and vertical position that lacks power and lacks comfort on longer rides. Al though we could not find a reliable measurable method to his excellence, he says that if you drop a line from the tip of the seat down it should be at least 40mm behind the BB centre. I believe after doing the knee method it is worth checking your seat / BB offset but is not a reliable measure due to so many different shape seats and different sit positions on each seat. Too far back with the same stem reach will close your abdomen and require a sharper back curve and can cause sore lower back and more restricted breathing.
Knee method
Put your bike in a stationary trainer, and make sure to raise the front wheel so the bike is level. Position the ball of your foot directly over the pedal axle. Take a small ride to relax and settle into a natural position.
While you continue to look ahead, slowly stop pedalling, and bring the cranks to rest at horizontal, parallel to the ground. Check the position of your forward knee relative to the pedal spindle —for a "neutral knee position," you’ll be able to drop a plumb line or level from the little hollow immediately below the outside your kneecap, and have it run directly through the pedal spindle and ball of your foot below. Remember to not raise or drop your heel or hip as you check this. Then, move the saddle fore or aft, as need, to achieve this neutral position.
We correct the position by loosening the seat post saddle clamp bolt and sliding the seat forwards or back until the line falls in the acceptable range. The longer the femur, the more it should be "pushed back"
The neutral knee position serves as a good starting point for most cyclists, although many adjust it from here: long distance (stage) racers and mountain bikers often move the saddle back up to 1cm, for heeling the pedal in climbs, and sprinters may move it forward for toeing the pedal for faster pedal speed. Moving your vertical line in front of the pedal spindle can result in pain in your knee and subsequent injury.
One more note on frame size and geometry: if you cannot move the saddle enough to get your knee to the neutral position, you should look for a frame with a different seat tube angle or different frame size.
Finally, recheck your saddle height. If you’ve moved your saddle forward or back, you’ve effectively shortened or lengthened your saddle height, and will need to readjust it.
