To follow up on how to consistently reproduce your saddle position time after time, I would be remiss if I did not address fore/aft position. Saddle position, much like your handlebar position, is measured in two planes. The X (horizontal) and Y (vertical). Both these measures are taken from one central landmark on the bike, your bottom bracket.
Here are two way to accurately measure your fore/aft position and make documenting and reproducing your saddle position reliable and consistent.
The first method is with a traditional weighted line. Here you will have your bike off the trainer with the line going right over the tip of the saddle. The line should be long enough to drop past the chainstays and bottom bracket.
PRO TIP: You will want to tip your bike slightly toward you to allow the weighted line to hang freely without interference from the frame or cables. Cyclocross and Mountain Bikes in particular tend to have wider top tubes and stays which can interfere with the path of your line.
Take a ruler or tape measure and align it with the center of your bottom bracket. Let the weighted line settle to a consistent point.
There is your fore/aft position! 9.1 cm is the example used in this post.
The second method will give you the same result without having to remove the bike from the trainer. Most people I know will not pass up the opportunity to play with lasers. Cats like lasers, kids like lasers, DIY homeowners like lasers, and bike fitters are no different. We love lasers! and use them any time we can to get an accurate straight line assessment.
Line up your laser with the center of your bottom bracket. I have made it a habit of using the non drive side because there are many cranks without a good center point on the drive side.
Take your tape measure and line it up on the tip of the saddle
That’s it! 9.1cm is the number in this example.
You are all set to get your saddle dialed in after any maintenance, changes in seatpost, and to replicate your position on a similar style bike with the same saddle.