Stack Height

DB4 said:

Hi

I need to buy a new headset for my MTB. (older style threaded 1 inch) The
retailers on the web refer to 'stack height'. I'm guessing this relates to
how much of the fork stem you have available for the headset in question but
what exactly does the dimension refer to? What do I measure to check the
stack height of my existing headset?

Most threaded 1" headsets are made to fit a fairly narrow stack height
range; I have seldom encountered a situation where a replacement 1"
threaded headset didn't work due to this issue. It's not hard to find
out what stack height you have now, however. Just measure the length
of the head tube on your frame, and then measure the distance from the
bottom of the lower bearing to the top of the nut; the difference
between these two measurements is the stack height. If the
replacement headset has a higher stack height, beware; it probably
won't work. If the replacement headset has a lower stack height than
what you have now, it will work; you may want to add a washer or
spacer (as needed) to fill the extra space instead of cutting down the
tube. The spacers may already be present in your old headset, in
which case you can simply recycle them. BTW, the little tab on the
inside of the washers is completely unnecessary; a tabless spacer
works just fine.

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Werehatrack said:

DB4 said:

Hi

I need to buy a new headset for my MTB. (older style threaded 1 inch) The
retailers on the web refer to 'stack height'. I'm guessing this relates to
how much of the fork stem you have available for the headset in question but
what exactly does the dimension refer to? What do I measure to check the
stack height of my existing headset?

Most threaded 1" headsets are made to fit a fairly narrow stack height
range; I have seldom encountered a situation where a replacement 1"
threaded headset didn't work due to this issue. It's not hard to find
out what stack height you have now, however. Just measure the length
of the head tube on your frame, and then measure the distance from the
bottom of the lower bearing to the top of the nut; the difference
between these two measurements is the stack height. If the
replacement headset has a higher stack height, beware; it probably
won't work. If the replacement headset has a lower stack height than
what you have now, it will work; you may want to add a washer or
spacer (as needed) to fill the extra space instead of cutting down the
tube. The spacers may already be present in your old headset, in
which case you can simply recycle them. BTW, the little tab on the
inside of the washers is completely unnecessary; a tabless spacer
works just fine.

I even omitted the washer at my own peril when replacing an indexed
Tange Levin with a Shimao headset. "This should loosen or cause
environmental disasters" I thought. Nope, still tight and perfectly
adjusted over a year later.