Getting your seated position right is one of the fundamentals of cycling. The hobby takes enough out of you as it is without throwing discomfort into the mix. If you are potentially in that saddle for three hours plus, you need to be comfortable!
The other side of having the correct saddle position is reducing muscle fatigue and avoiding injury wherever possible. If you’re stretching your legs too much, having to compensate one leg for the other or dipping your hip too much you will tire faster than you would usually. Getting your cycling position right can help avoid all that.
There are as many theories and ways of measuring the ‘ideal’ saddle height as there are saddles. Personally, I used trial and error to find my ideal saddle height. The method that came closest was the Greg Lemond method. Measure your inside leg while wearing your bib shorts and set the seat height at 88.3% of that measured from the saddle to the centre of the bottom bracket.
Saddle height isn’t a fixed position though. While this works for me with my 172.5mm crank arms, it might not work for you. A good measure is to clip into the pedals and have your leg just short of full extension when the pedal is at the 6 o’clock position. Then, when cycling, you should be able to pedal without moving your hips too much. If you do dip your hips, lower the saddle by a couple of mm.
A good way to measure this is to sit on the very edge of a table or kitchen worktop and relax your legs. You will see that they don’t hang straight when relaxed. It is that angle we want to replicate with your saddle height.
Rinse and repeat the adjustments until you’re completely comfortable.
Saddle fore and aft position
Setting the correct lateral position is also important, but thankfully much easier to do. Sit on the saddle in your usual riding position and set the pedals at 3 and 9 o’clock. Have a helper use a plumb line or spirit level and measure from the little bump just under your knee down to the 3 o’clock pedal axle.
A good fit will be when the bump is between 1cm behind and level with the pedal axle. Adjust and test as you see fit.
Unless a professional bike fit or experience tells you otherwise, the saddle should be level with the ground. Using your spirit level, lay it on top of the saddle and adjust it until level. Only adjust from this position if you find it uncomfortable or a fitter tells you otherwise.
Setting your saddle up this way gives you a good foundation from which to tweak your settings. When shifting position, start small, 2mm or so and ride for a while to test. Your body adapts to the smallest changes so you need to give it a few miles to see if it is really comfortable or not.