Originally Posted by
HardyWeinberg
You want your leg at full extension when the crank arm is parallel w/ the seat tube, which is to say when the pedal is at 6 o'clock you should have a bend in your knee.
Another rule of thumb, if you can't decide if the bend in your knee is too much bend or too little bend or just right bend, if you put your
heel on the pedal at bottom of stroke, you should just be able to reach the pedal with a fully-locked straight leg. Then when you actually pedal with the
ball of your foot, you will have a good amount of knee bend at the bottom of the stroke.
Another rule of thumb goes I think something like this: pain the front of the knee, your saddle is too low; pain in the back of the knee, your saddle is too high. I think that's how it goes, maybe I got it backwards. Hopefully somebody else can confirm.
Also this I know for sure (from experience): pain at the
outside of your knees, your pedals are too close together, you normally walk with duck feet and you need pedal extenders so your legs are not artificially twisted straight.