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  1. #1
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    Threaded fork question - length vs headtube

    I have a 55 cm soma rush w/a 130mm headtube. Theres currently a soma straight blade threaded fork that is 170mm threaded, I was wondering if that would work with my frame.

    Here is the ad: http://sfbay.craigslist.org/eby/bik/2023762998.html
    The fork: http://store.somafab.com/sostbltrfo.html (1" 170mm threaded)
    The frame: http://store.somafab.com/sorutrfr.html (55cm)

    Thanks guys. If it doesn't work, no big deal, I wasn't exactly expecting to go threaded anyway.

  2. #2
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    Head tube length + stack height of the headset = your answer.

    I think you will be fine using that fork, you might not even need to cut it.

    On a related note, I recently removed and install my headset for the first time, it was frustrating but I felt quite successful.

  3. #3
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    Thanks, vix. How do I know which one of these to picK? One of them has a 26.4 race and the other 27.0, whats the difference?

    http://www.benscycle.net/index.php?m...54757ce2fc5f7e
    http://www.benscycle.net/index.php?m...54757ce2fc5f7e

  4. #4
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    Actually now that I think about it...they might not work, the stack height of your headset is 30mm, which will leave you 10mm of space for your top race and a locknut.

    That's the different between ISO and JIS forks, ISO (26.4mm) are the "standard" size for 1" headset, whereas JIS (27mm) are not common as ISO.

    I would ASSUME that it is an ISO fork...it most likely is, JIS were(are?) used on lower end bikes.

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    There will probably be no spacers then, that or it wont work.

  6. #6
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    Nevermind my mumble jumble, after digging through the internet, the measurement of stack height includes both the lock nut and spacer...so you should be fine.

  7. #7
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    I posted this in bicycle mechanics a few minutes ago, whoops.

    Looks like I have my answer from you.

    Thanks!

  8. #8
    Senior Member osiris419's Avatar
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    The way that seems to work for me is to measure the headtube with the headset cups installed and use a fork that is about an inch longer or so longer. the main thing to make sure of is that the fork is threaded enough to have the headset tighten properly and that it's long enough to get the lock nut on. If it's a littke too long you can always use spacers in between.
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  9. #9
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by xkillemallx16 View Post
    Thanks, vix. How do I know which one of these to picK? One of them has a 26.4 race and the other 27.0, whats the difference?

    http://www.benscycle.net/index.php?m...54757ce2fc5f7e
    http://www.benscycle.net/index.php?m...54757ce2fc5f7e
    26.4mm race seat = ISO
    27.0mm race seat = JIS

    When in doubt, measure your fork. When unable to measure, get ISO and prepare to have your LBS mill the race seat on the fork to fit if necessary.

    The "Passage" headset has a 30.3mm stack height, so as long as your steer tube (measured from the race seat to the top of the steer tube) is at least 30.3mm longer than your head tube you should be ok. Remember, you can always add spacers if your steer tube is too long (or simply trim it down), but if it's too short you're SOL.
    Last edited by JohnDThompson; 10-25-10 at 01:33 PM.

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