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What is "Stack Height"?(19 posts)

What is "Stack Height"?Lee M
Mar 25, 2001 7:29 PM
What is "stack height" and why do I have to know that when I buy a new headset? I stack height an issue for threadless headsets?
re: What is "Stack Height"?Jamie harris
Mar 25, 2001 7:36 PM
It is the height of all parts of the headset as if it was on the bike. It is important if you do not have alot of steer tube length on your fork. I had to use a real low stack height headset on my mt. bike, or my stem would not slide down far enough on the fork. Generally, if done right, you should have a spacer on your steer tube between the headset and stem to take up the extra steer tube length, but you may need a low stack height headset if you do not currently have a large spacer between the headset and stem. Do you follow?

re: What is "Stack Height"?Spoke Wrench
Mar 26, 2001 5:22 AM
Stack height is the difference between the length of the head tube on the bike frame and the length of the steer tube on the fork. Whether your headset is threaded or not, that difference has to be made up by the headset and spacers.

On threaded headsets, handlebar height adjustment is done with the stem. If you have a relatively short steer tube you may have to hunt aroung for a headset with a low stack height to get everything to bolt up adequately.

With threadless headsets you will almost always have to have spacers in the mix to get the handlebar high enough. Consequently, the stack height of the headset itself doesn't matter as much.
re: Stack Height...?See Jamie's Definition........
Mar 26, 2001 5:51 AM
Danger! Danger!Will Robinson
Mar 26, 2001 9:51 AM
see Jamie's post for correct answer
All right, what did I say that's wrong?Spoke Wrench
Mar 26, 2001 11:18 AM
That's two criptic posts that imply that I said something wrong, but I don't see what it is. What am I missing?
All right, what did I say that's wrong?Try This.....
Mar 26, 2001 12:31 PM
You don't have to have either a headtube or steerer tube to determine stack height. It's a manufacturers spec.It' the vertical space the headset occupies when its installed. Its one of the the things,like headtube length,you need to know when making a buying decision on a fork.The steerer has to be long enough to acomodate the stack height and the length of the headtube, and the stem in the case of threadless.Threadless forks come in one very long lengths and have to be cut,and stack height,stem height, headtube length and amount of spacers desired, determines how long to cut it. Again, see First sentence of Jamies post.
That's really the exact same thing that I said.Spoke Wrench
Mar 26, 2001 3:09 PM
The only difference is: you are talking about the headset itself and I'm talking about the space where it fits. The advantage of my way is, if I am working with a fork that has a short steer tube, I'll know exactly what stack height I have to look for in a headset. If the steer tube is long, I can order a spacer the right thickness to fill the space.
totally wrong...dave
Mar 26, 2001 2:45 PM
The stack height of a headset has nothing to do with steering tube length or the head tube length. It is the total height of all the headset parts "stacked up". Exactly what it implies. It is a lot more critical with a threaded headset.

If you try to replace an existing threaded headset with a new one which has a longer stack height, there won't be enough threads left to engage the locknut, unless the original setup used a spacer under the locknut, which could be removed.

Mass produced bikes may use spacers under the locknut, but a good mechanic will always cut the steering tube tube to the exact length required, without spacers, for a cleaner look.
That's like saying shoe size has nothing to do with foot size.Spoke Wrench
Mar 26, 2001 3:16 PM
just face it- you're wrongD'Oh!!!
Mar 26, 2001 4:10 PM
the truth hurts sometimes, but the big man stands and admits it
You just don't get it.......Sydnie
Mar 26, 2001 5:02 PM
Headset stack height is a stand alone value. Typically expressed in mm, as in 37.5mm for the Shimano Dura Ace or ultegra.
5 different responders, not one clue.Spoke Wrench
Mar 26, 2001 5:30 PM
Why does it matter that a Shimano headset has a 37.5mm stack height?

It matters because it has to fit in a certain space. If I were fitting a bottom bracket to a bike, I could either measure the bottom bracket shell to see if it needed a 68 or 73mm bottom bracket, or I could try different components until I stumble on a combination that fits. Same thing if I'm replacing an old headset, I'm going to measure the space where it goes so that I will know what size headset I need to order. That's the reason that suppliers publish headset stack heights.

If you can't understand this, you don't need to know what the headset stack height dimensions are, because you are doomed to assemble your fork by trial and error anyway.
re: What is "Stack Height"?bruceg
Mar 26, 2001 6:08 PM
Hmm, threaded is 1 definition, threadless another.TNC
Mar 26, 2001 7:38 PM
And actually, just about all of these descriptions were right in principle. I think everyone understood the issue, but it just turned into a hair splitting exercise. Good source info, Bruce.
Hey ,thanks man......nm.I feel better already!
Mar 27, 2001 10:37 AM
Inversely Related to Cup Sizegrz mnky
Mar 28, 2001 8:13 AM
At least that's what I learned when I was single....
Gives a new meaning to "700 c" (nm)Spoke Wrench
Mar 28, 2001 8:28 AM
Best thread for a while....muncher
Mar 29, 2001 6:59 AM
Half full - no half empty -NO half full - NO HALF EMPTY - NO! HALF.... The long-lost art of lagomorphic sub-division....