Tapered Headset/ Fork Question

Samvan77 Posts: 85
edited January 2014 in Workshop
Hi everyone,

Really silly question, but can someone please explain to me in layman's term how the concept of a tapered fork steerer and headset works?

I have a frame(Boardman Carbon) without a fork, the original spec of the bike reads that the bike comes factory fitted with a for a fork with a tapered steerer on a FSA Orbit C-40 ACB/Industrial 1.1/8” to 1.1/2” Tapered - Integrated headset.

So am a I correct in understanding that that the bottom crown race of the headset will 1.1/8" and the top crown race 1.1/2"? And does that mean that only tapered forks and headsets can be fitted to the frame?


  • dj58
    dj58 Posts: 2,221
    TAPERED HEADSETS Info from FSA website

    Tapered headsets are a combination of the other styles. Usually a tapered steerer tube will have a 1 ¼” or 1.5” lower diameter, and a 1 1/8” upper diameter. The headsets for these frames & forks can be any combination of traditional, internal, or integrated headsets. It is very important to accurately measure the inner diameter of the headtube top and bottom to narrow down the headset model needed. In some cases, Tapered headtubes can be used with a straight 1 1/8” steerer tube if a reducing headset race is used.

    Orbit C-40
    Integrated headset with upper angular contact bearing and lower sealed bearing.
  • maddog 2
    maddog 2 Posts: 8,114
    1 1/8" is the diameter of the top of the steerer

    1 1/2" is the bottom

    You can fit a straight 1 1/8 fork but it gets messy as you'll need a crown race which converts from 1 1/8 to 1.5, so I'd advise against it.

    Other than that, you just need to match the crown race to the lower headset bearing. If the crown race is a separate item then this is easy as all the parts come in the headset box. However some forks have integrated crown races (e.g. Giant TCR forks) so you need to match the angle of the surfaces. So a 45deg crown race matches to a 45 degree headset bearing.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • smidsy
    smidsy Posts: 5,273
    In basic terms the head tube is wider at the bottom than it is at the top (smaller number is the bigger size).

    What this does is ensure that you get the stiffness at the botton where you need it but then save weight by having less material at the top (plus a cone is stonger than a straight tube).

    You can get tapered forks that mesh with the tapered head tube or you can fit straight forks and take up the difference with an appropriate adaptor bearing.


    Look closely and you will see the head tube is wider at the bottom but the fork steerer is a straight tube.
    Yellow is the new Black.
  • Cheers guys! You have all given me some really useful input here!