How stem angle and spacers move your bars
Understand the two directions hidden in a spacer change.
Spacers move up and back
A steerer is normally tilted backward. At a 73° head angle, adding 10 mm along the steerer raises the stem axis about 9.6 mm and moves it back about 2.9 mm. The calculator resolves both components rather than treating spacer height as a purely vertical change.
A negative stem angle is not a ground angle
The modeled stem inclination above horizontal is 90° minus head angle plus installed stem angle. A −6° stem on a 73° head angle points 11° above horizontal. Flipping a stem changes its installed angle, so verify the marking and manufacturer convention.
A mathematical target is not a shelf part
The exact solution can require a nonstandard length or angle. The trial list ranks sampled combinations by straight-line clamp offset, keeping candidate rise fixed. Availability, cable routing, handling, and installation limits are not checked.