threaded headset stack height calculation..?

fonebone3
fonebone3 Posts: 20
edited May 2008 in Workshop
I need to buy a new 1" threaded headset for my winter bike but I am being confronted with 'stack height' while trying to buy one... What is it?

I have measured up the bike and I'm hoping someone can give me some free advice:

1) From the top of the forks shoulder, where the bottom of the existing headset bearing housing rests, to the bottom of the headtube = 12.8mm

2) From the top of the headtube to the top of the forks thread, with the existing headset locking ring removed, = 22.5mm

3) Therefore, is the stack height 12.8 + 22.5 = 35.3 ?????

Many thanks in advance for all your speedy replies - this is an emergency as I haven't got my summer bike together yet either.

Comments

  • nick hanson
    nick hanson Posts: 1,655
    Sounds like you are right on the money,there.
    Stack height is only an issue if you had a very 'compact' headset fitted before,& you buy a 'tall' replacement.
    so many cols,so little time!
  • fonebone3
    fonebone3 Posts: 20
    thanks for the reply Nick, but i'm still none the wiser...

    ..I have no inbuilt concept of whether these measurements add up to 'compact' or 'tall' in the first place... plus, Stack Height is an issue when you want to buy a headset.

    To extrapolate the original post: What is Stack Height and how does it relate to the frames measurements?

    tia
  • Pirahna
    Pirahna Posts: 1,315
    Stack height is the additional height a headset adds to the front of the frame. For example, without a headset the head tube measures 150mm, with the headset fitted the measurement from the bottom bearing to the top of the nut is 180mm - the headset has a 30mm stack.

    Shimano and Stronglight have a low stack, Campag will have a high stack.
  • fonebone3
    fonebone3 Posts: 20
    Thanks Pirahna.

    So, if my forks steerer tube is 35.3mm longer than the head tube and there is a choice of a 37.3 stack height headset and a 33.3 stack height headset, which one do i vote for?
  • Pirahna
    Pirahna Posts: 1,315
    I'd go for the lower one, you can always put an extra washer between the top nut and the bearing.

    Edit: Thinking about it, either would be OK. With the higher stack you'll have a 2mm gap between the top of the steerer and the top of the nut which would be fine. Pick the one with the best bearings.

Categories