Threaded Fork converted to Threadless headset
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  1. #1
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    Threaded Fork converted to Threadless headset

    So why can't I use a threadless headset on a threaded fork? I couldn't answer that question. So I tried it before intalling. I put the threadless headset over the threaded fork and put the threadless stem on and all looked good. So I cut the threaded fork to length put my start nut in and commensed to installing the items. It worked well for me. Test ride was perfect. I can't believe I'm the only one who has thought of this??

  2. #2
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    As long as your stem isn't clamped on the threaded portion, you should be fine; otherwise, hello stress riser!

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    Quote Originally Posted by Bremerradkurier View Post
    As long as your stem isn't clamped on the threaded portion, you should be fine; otherwise, hello stress riser!
    Actually the stem is clamped on the threaded portion. I don't foresee any problems there. I may be wrong but a threaded pipe vs a threadless pipe with the same wall diameter will handle same amount of clamped stress as the other.

  4. #4
    tlg
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    Is your threaded fork 1" or 1-1/8"?

    Why do you think you're the only one who has thought of this?
    http://forums.roadbikereview.com/com...ed-154586.html
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  5. #5
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    Quote Originally Posted by Agent319 View Post
    Actually the stem is clamped on the threaded portion. I don't foresee any problems there.
    Does the thread extend below the stem? Or is the threaded portion entirely within the clamping area of the stem?

    If any of the thread is below the stem, or even close to the bottom, you've got a potential problem.

    I may be wrong but a threaded pipe vs a threadless pipe with the same wall diameter will handle same amount of clamped stress as the other.
    You're kinda wrong. If both ID and OD are the same, and you cut a thread into it, you have less wall thickness.

    This would only be true if the wall thickness from the root(bottom) of the thread to the ID was the same. The threaded pipe would need a larger OD or smaller ID. But even then, the threaded pipe would be weaker because as Bremerradkurier mentioned, you have a stress point at the root of the thread.
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    Quote Originally Posted by tlg View Post
    Is your threaded fork 1" or 1-1/8"?

    Why do you think you're the only one who has thought of this?
    http://forums.roadbikereview.com/com...ed-154586.html
    It is a 1" threaded fork

    I checked the forum you listed but all it talks about is changing from Threaded fork to Threadless fork. I'm using my Threaded fork with a Threadless stem.

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    I think you have to judge the steer, case by case (even though they should all be standard). I did a partial same to a tourer years ago. I could only find a fork, fully threaded, so I ran an old WTB by CK headset on it and clamp stem above. Round the world, huge stress, lots off-road, but the STEEL steer tube was too damn stout w the threads. Most will recommend against it theoretically, and I wouldn't let anyone else at it. Personal decision.
    Last edited by grandsalmon; 09-07-2012 at 10:11 AM.

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    The type of stress that a threadless stem puts on a steerer tube is way different than the threaded type. Look at it this way, with a threaded system, the tube is cut at the top of the headset. There is no leverage on the steerer tube. With the threaded, you have the force of the stem both clamping on the tube and there is leverage on the section. An unthreaded tube can take that stress, but when you cut threads in it, you significantly compromise the strength. There is a very real risk this steerer tube will crack just below the stem, if you're lucky it won't break clean off when you are flying down a steep hill and hit a bump. Hello stress riser, indeed.

  9. #9
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    You can always fill the threads with epoxy puddy, sand it out to make it smooth...

    Steel forks will not give out catastrophically like alumninum will. (or carbon). You will know when your fork is about to fail with steel.
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  10. #10
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    Quote Originally Posted by Agent319 View Post
    It is a 1" threaded fork
    So you got a 1" threadless headset?
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  11. #11
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    Quote Originally Posted by CleavesF View Post
    You can always fill the threads with epoxy puddy, sand it out to make it smooth...
    That will do nothing to add strength.
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    Quote Originally Posted by tlg View Post
    So you got a 1" threadless headset?
    Yes I have a 1" threadless headset with a threadless stem attached to a threaded fork.

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    Quote Originally Posted by tlg View Post
    Does the thread extend below the stem? Or is the threaded portion entirely within the clamping area of the stem?

    If any of the thread is below the stem, or even close to the bottom, you've got a potential problem.

    You're kinda wrong. If both ID and OD are the same, and you cut a thread into it, you have less wall thickness.

    This would only be true if the wall thickness from the root(bottom) of the thread to the ID was the same. The threaded pipe would need a larger OD or smaller ID. But even then, the threaded pipe would be weaker because as Bremerradkurier mentioned, you have a stress point at the root of the thread.
    The threads extend below the stem.

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    Quote Originally Posted by grandsalmon View Post
    I think you have to judge the steer, case by case (even though they should all be standard). I did a partial same to a tourer years ago. I could only find a fork, fully threaded, so I ran an old WTB by CK headset on it and clamp stem above. Round the world, huge stress, lots off-road, but the STEEL steer tube was too damn stout w the threads. Most will recommend against it theoretically, and I wouldn't let anyone else at it. Personal decision.
    If this fork handled it and this guy is still alive then I think Myth Busters would call this myth busted that a threaded fork can't handle a threadless stem

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    Quote Originally Posted by tlg View Post
    Does the thread extend below the stem? Or is the threaded portion entirely within the clamping area of the stem?

    If any of the thread is below the stem, or even close to the bottom, you've got a potential problem.

    You're kinda wrong. If both ID and OD are the same, and you cut a thread into it, you have less wall thickness.

    This would only be true if the wall thickness from the root(bottom) of the thread to the ID was the same. The threaded pipe would need a larger OD or smaller ID. But even then, the threaded pipe would be weaker because as Bremerradkurier mentioned, you have a stress point at the root of the thread.
    Yes I agree that a threaded tube is weaker than a non-threaded tube but what amount of stress in Flbs will this have on it during bike riding. I can't believe the sheer stress will be that much.

  16. #16
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    Quote Originally Posted by Agent319 View Post
    Yes I have a 1" threadless headset with a threadless stem attached to a threaded fork.
    Nothing wrong with that then.

    Quote Originally Posted by Agent319 View Post
    The threads extend below the stem.
    As mentioned by several people... not a great idea.

    If this fork handled it and this guy is still alive then I think Myth Busters would call this myth busted that a threaded fork can't handle a threadless stem
    That proves ABSOLUTELY nothing. You've come to a "scientific" conclusion based on a single anecdotal story on the internet? Adam and Jamie would be ashamed.

    Do you have the same fork? Do you ride the same conditions? Are you the same weight?
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  17. #17
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    Quote Originally Posted by Agent319 View Post
    Yes I agree that a threaded tube is weaker than a non-threaded tube but what amount of stress in Flbs will this have on it during bike riding. I can't believe the sheer stress will be that much.
    You're welcome to believe there isn't much stress on a steerer tube.

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  18. #18
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    Quote Originally Posted by Agent319 View Post
    Yes I agree that a threaded tube is weaker than a non-threaded tube but what amount of stress in Flbs will this have on it during bike riding. I can't believe the sheer stress will be that much.
    Think of all the fatigue cycles working on the very small area of the thread valley right at the bottom of your stem during a ride of just ten miles, remembering that the inputted force is at least your upper body weight working with a minimum lever length of 4" (bar tops, 100mm stem) to as much as 9" (brake hoods, 120mm stem).

  19. #19
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    Quote Originally Posted by Bremerradkurier View Post
    Think of all the fatigue cycles working on the very small area of the thread valley right at the bottom of your stem during a ride of just ten miles, remembering that the inputted force is at least your upper body weight working with a minimum lever length of 4" (bar tops, 100mm stem) to as much as 9" (brake hoods, 120mm stem).
    Then throw in the impact force from hitting a pothole. It will easily spike the forces up 5x-10x.
    There's no suspension on a road bike and the tires are at a high PSI. All those forces drive right up through the fork and stem.

    I use to work in the railroad industry. We had to design for massive G forces. The bearings on a train car can see up to 20 G's just from a little bump in the tracks. It's amazing what happens when you don't have a suspension.
    Last edited by tlg; 09-07-2012 at 12:08 PM.
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  20. #20
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    lol, this is such a bad idea...

    I am pretty sure the wall thickness on threaded steer tubes are different than threadless, btw...

    Love how people will risk their lives to save the $40 or whatever...
    I hate you all

    j/k lol kthxbye!

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    Quote Originally Posted by foto View Post
    lol, this is such a bad idea...

    I am pretty sure the wall thickness on threaded steer tubes are different than threadless, btw...

    Love how people will risk their lives to save the $40 or whatever...
    The idea isn't all that bad, and plenty of shops out there probably have old stock threaded forks for circus freak sized 63cm + frames preserved under an inch of dust that could easily be cut below the threads and used in threadless headsets.

    Remember, a lot of the change to threadless steer tubes in the bike industry was due to how easy it made fork inventory-one size for all size frames vs. having to match the threaded length to each range of frame sizes.

  22. #22
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    Quote Originally Posted by Bremerradkurier View Post
    The idea isn't all that bad, and plenty of shops out there probably have old stock threaded forks for circus freak sized 63cm + frames preserved under an inch of dust that could easily be cut below the threads and used in threadless headsets.

    Remember, a lot of the change to threadless steer tubes in the bike industry was due to how easy it made fork inventory-one size for all size frames vs. having to match the threaded length to each range of frame sizes.
    good point, but not really what the discussion was about. The OP is clamping a threadless stem to the threads of a threaded fork.

    This is a bad idea. Would make more sense to me to get a shop to cut some more threads in the steerer, cut off the top, and use a quill stem. But that's me. I don't like worrying about whether my handlebars are going to come flying off when I am riding. Personal opinion here...

    It would look a lot better, too.
    I hate you all

    j/k lol kthxbye!

  23. #23
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    Quote Originally Posted by CleavesF View Post
    You can always fill the threads with epoxy puddy, sand it out to make it smooth...

    Steel forks will not give out catastrophically like alumninum will. (or carbon). You will know when your fork is about to fail with steel.
    Haha! Steel will not fail catastrophically? Are you suuuuuure?
    I hate you all

    j/k lol kthxbye!

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    Quote Originally Posted by foto View Post
    lol, this is such a bad idea...

    I am pretty sure the wall thickness on threaded steer tubes are different than threadless, btw...

    Love how people will risk their lives to save the $40 or whatever...


    In this "throw away society" I'm just doing my best to recycle.



    I risk my life everyday just getting out of bed and driving to work.


    Heck, now that you mention risk I'm going to throw a quote out there from the movie "Diliverance"... "I've never been insured in my life. I don't believe in insurance... there is no risk."

  25. #25
    tlg
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    Quote Originally Posted by CleavesF View Post
    Steel forks will not give out catastrophically like alumninum will. (or carbon). You will know when your fork is about to fail with steel.
    That is officially the worst thing I've ever read on this site.

    If the stress exerted on the steel exceeds the strength of the steel, while you are riding, you will achieve catastrophic failure.
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