Originally Posted by MattP.
I'm having trouble picturing how this is. It was my assumption, that (for the sake of example) you had a headset w/ a lower stack height of 2 in. Wouldn't the front end feel much higher than if you were running a headset w/ a lower stack height of 15 mm? Isn't adding/taking away from the lower stack height, going to have the same effect as playing around w/ the A to C height of the fork? Thus changing the head angle?
Now, that is only when playing with the lower stack height. If anything is added/subtracted to the upper stack height, yeah, head angle is not going to be affected.
What you're describing, is the height of the stem/handlebar. The head angle does not change.
If you were to add spacers under the headtube it would change. But when dealing with over the head tube, nothing changes. Just look at a bike with a fork with no stem/spacers and you'll see that nothing changes if you start stacking up spacers or leave nothing on.
Sorry - just read through with respect to the headset stack height and not spacer height. I'm tired. Off to bed.