Stem Angles and Steerer Tube Spacers

Part A: Stem Angle and Bar Height Change

By playing around with stem angle, we could achieve the ideal handlebar height in situations where:

The steerer tube was cut too short and there's no possibility to increase handlebar height using spacers.
The frame Stack is too tall and we couldn't lower the handlebar height enough.

If you're interested in knowing how much difference in handlebar height when a stem is flipped upside-down, or when swapping with a different angle stem, here's a reference guide for you:

Quick explanation on how to read the chart above:

i) Stem Flipping:

With a 80mm & 6 degree stem in the negative position (slanting down), we will get a 17mm increase in handlebar bar height when flipping the stem to positive position (slanting up).

ii) Changing Stem Angle:

When we change a 100mm 6 degree stem to a 100mm 17 degree stem (both in negative position) the handlebar height is lowered by 17mm.

Part B: Measuring Steerer Tube Spacers

Sometimes i noticed many would make a mistake by not including the headset cover thickness when mentioning steerer tube spacer height.

As there is no common headset cover thickness, although bike manufacturers usually include a 15mm tall cover with frames, but we do get the occasional 10mm, 20mm or even 25mm cover being installed.

If we solely mention the steerer tube spacers without including headset cover, the handlebar height can be very much in the wrong position when we transfer the fit numbers onto a different frame, and this would cause upper body strain.

Here's a diagram showing the correct measurement for steerer tube spacer height: