Stack height?

on-yer-bike
on-yer-bike Posts: 2,974
edited November 2014 in Road general
How can two frames with different headtube lengths have the same stack height?
Pegoretti
Colnago
Cervelo
Campagnolo

Comments

  • wishitwasallflat
    wishitwasallflat Posts: 2,927
    Is stack height not often quoted about headsets so could it be the height above the top of the head tube to the top of the stem (i.e. spacers etc) so head tube length is not involved?
  • styxd
    styxd Posts: 3,234
    different fork lengths.
  • freefall_junkie
    freefall_junkie Posts: 123
    3 factors affect a frame's stack height: head tube length, head tube angle and bottom bracket drop. Technically fork rake also makes a difference although it will be very small. I found this calculator to be very useful when comparing frames from manufacturers who didn't publish the stack and reach measurements: http://bb2stem.blogspot.co.uk/

    The frame stack height measurement does not include headset or spacers, but this calculator allows these to be added to work out the 'true' stack and reach.
  • mikenetic
    mikenetic Posts: 486
    freefall_junkie wrote:
    3 factors affect a frame's stack height: head tube length, head tube angle and bottom bracket drop. Technically fork rake also makes a difference although it will be very small. I found this calculator to be very useful when comparing frames from manufacturers who didn't publish the stack and reach measurements: http://bb2stem.blogspot.co.uk/

    The frame stack height measurement does not include headset or spacers, but this calculator allows these to be added to work out the 'true' stack and reach.

    Stack is the total vertical accumulation of height from the centre of the bottom bracket to the top of the centreline of the head tube. The lower headset depth and fork axle to crown measurement both need to be taken into account with the BB drop when looking at the head tube length.

    stack_and_reach.png

    So, to the OP's question, fork length and headset style can make quite a difference. A winter road fork is about 10mm longer axle to crown, an external lower headset cup will also shorten the head tube for a given stack when compared to an integral or integrated lower bearing system. Cyclocross forks make the HT even shorter, as they are so long. BB drop normally only varies by a few mm, but it does have an effect too.

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