cazorp, assuming this is for XC all mountain type of riding
To get the most out of what is currently on your bike, follow these simple steps:
1) Measure and record everything: This step is very useful when your bike is disassembled and then put back together.
a. Saddle height from center of the pedal spindle or center of the crank to the center and top of the saddle in line with the center of seat post (some bike have odd bends in the seat tubes) so there is a difference between actual and effective seat tube angles.
b. Fore aft measurement, I measure from the center of my handlebar to the nose of the saddle
c. Tilt is generally measured in degrees, simplified is method is to measure from top of the tube to bottom of the saddle nose.
2) Make small changes about 1 cm or less unless it is very obvious the saddle position is way off.
3) Ride with each change for at least a couple km if it doesn’t feel worse, if the bike feels better with the change do it again until it does feel worse then back off to the place it was before the last change.
4) Be aware that a change in fore aft will effect the saddle height aft makes it higher fore makes it lower. But resist the urge to change both at the same time unless you have already.
What your body is telling you about your saddle and overall bike position. These are suggestions, though some symptoms can be from over use and under rest or other biomechanical reasons and you may need to be evaluated by a qualified sports medicine professional.
Hips should remain somewhat level when pedaling on the saddle if they rock high to low then the saddle is most likely too high and will lead to low back and hip pain if not already. You may also notice that you pedal on your tippy toes like a ballerina to compensate.
Heels should flat at the bottom of the stroke, like scraping mud from your shoes at the bottom of the stroke. More on this in how to pedal effectively. If your heals are really low at the bottom of the stroke you may need to raise the saddle height.
Back of knee pain could indicate a to high saddle or to much aft position.
Front of knee pain could mean a to low or too much fore position, sometimes too long of a crank.