Good day, I'm new to the whole bike building process, but I've finally decided to make the step and build a semi-nice bike.

I've bought a really nice aluminium frame 2nd hand, but its sizing has me stumped. The inside diameter of the front part of the frame (where the front fork goes in) is ~32mm. I've been searching online (e.g. http://www.sheldonbrown.com/cribsheet-headsets.html) for a couple of days, but I cannot understand what type of fork I should get.

Should I get an 1 1/8", 1.5" or some other type of fork?

EDIT: After some investigation, the bike frame is an Alpinestar Almega DX, the same as in this picture enter image description here I couldn't find any specs though :(

Here is what I measured, when I said it was ~32mms (apparently it's the headset, not the pipe itself). The other end is the same size. enter image description here


  • what kind of frame is it? It would be unusual for the fork size to not be provided along with the frame. Commented Apr 1, 2016 at 10:43
  • It's a "26, MTB frame.
    – hilchev
    Commented Apr 1, 2016 at 12:21
  • What I meant was, what make/model of frame is it? Does it have a headset fitted? Could you post a picture? Commented Apr 1, 2016 at 13:15
  • As mentioned, I bought it 2nd hand and it came as-is, with no other information and no stickers. There is a headset fitted. I can upload a picture at a later time. In a better world, I would have some information about what brand of frame it is, I would contact the maker and ask what fork is appropriate. However, since that is not the case, I'm asking if this size is something commonly seen or seen at all and under what name, since i'm a noob.
    – hilchev
    Commented Apr 1, 2016 at 13:28
  • Does the headset have anything marked on it? Commented Apr 1, 2016 at 13:29

1 Answer 1


If you have a 32mm approximate head tube inside diameter, this is an 1 1/8" frame, assuming it is a standard headset design.

An 1 1/4" head tube would have approximately a 35mm inside diameter.

Head tube sizing for traditional Headset

Here is a link to a PDF from Cane Creek detailing most other styles of headsets fitment for non-traditional options.

These have become very common also.

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