If my math is right, when you flip a 110 mm long, -10 degree rise stem and position it so that it has a positive rise, your handlebars will be 3.76cm higher. In other words, you could remove 3.76cm of spacers if you flipped the stem from its usual position.
Is there any reason why you would not want to do this in cases where you would otherwise have lots of spacers? This should give you a stiffer front end due to less of the steering tube protruding above the headset.
I went back and read the other thread and saw that it was a bit more esoteric. Hopefully the simple math I added on how to calculate the fit effect of flipping the stem helps people. I think it would be useful for us to come to a conclusion on how to apply stems and spacers when fitting bikes. Here’s mine: If you have over 4cm of spacers, remove the spacers and flip the stem. Your bike will be stiffer and safer. If you have less than 4cm of spacers, do the math and consider flipping your stem. If you are buying a bike new, consider the stem angle-- You could minimize spacers by choosing a stem with appropriate rise.
I put this out there for discussion, since so many people on this forum have over 4cm of spacers and negative rise stems.
Here is a table that shows the effect of flipping stems of various lengths and rises:
80 mm stem with a -10 degree rise gains 27.36 mm when flipped
90 mm stem with a -10 degree rise gains 30.78 mm when flipped
100 mm stem with a -10 degree rise gains 34.20 mm when flipped
110 mm stem with a -10 degree rise gains 37.62 mm when flipped
120 mm stem with a -10 degree rise gains 41.04 mm when flipped
130 mm stem with a -10 degree rise gains 44.46 mm when flipped
80 mm stem with a -8 degree rise gains 22.05 mm when flipped
90 mm stem with a -8 degree rise gains 24.81 mm when flipped
100 mm stem with a -8 degree rise gains 27.56 mm when flipped
110 mm stem with a -8 degree rise gains 30.32 mm when flipped
120 mm stem with a -8 degree rise gains 33.08 mm when flipped
130 mm stem with a -8 degree rise gains 35.83 mm when flipped
80 mm stem with a -6 degree rise gains 16.63 mm when flipped
90 mm stem with a -6 degree rise gains 18.71 mm when flipped
100 mm stem with a -6 degree rise gains 20.79 mm when flipped
110 mm stem with a -6 degree rise gains 22.87 mm when flipped
120 mm stem with a -6 degree rise gains 24.95 mm when flipped
130 mm stem with a -6 degree rise gains 27.03 mm when flipped
80 mm stem with a -4 degree rise gains 11.13 mm when flipped
90 mm stem with a -4 degree rise gains 12.53 mm when flipped
100 mm stem with a -4 degree rise gains 13.92 mm when flipped
110 mm stem with a -4 degree rise gains 15.31 mm when flipped
120 mm stem with a -4 degree rise gains 16.70 mm when flipped
130 mm stem with a -4 degree rise gains 18.09 mm when flipped