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  1. #1
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    1" steerer to 1 1/8" stem conversion

    I need to be sure I'm getting the proper parts I need for this conversion from a 1" stem to 1 1/8". The height of the steerer shim is greater than the 1 1/8" stem height and I have a 1" top cap. When I put this on, the 1" top cap will be compressing the shim and spacer stack while the 1 1/8" stem will have vertical play until tightened. Is that the way it should be done or will I need a 1 1/8" top cap and/or spacers?

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    use some 1 1/8 spacers and 1 1/8 top cap

  3. #3
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    Ideally that is the cleanest way to do it, but this is on my cross bike so I have a lot of steerer (85mm). The amount of steerer will be more than the height of the shim so there is not enough shim height to stack 1 1/8" spacers from the headset to stem. If I went with all 1 1/8" spacers, I would have to get extra shims to enable me to stack spacers like that. The spacers would then be stacked on diametrically uncompressed shims. Are there any issues with that?

    I'd like to stick with the 1" spacers if possible. Will it work safely with the 1" bits?
    Last edited by luckett; 12-30-10 at 07:01 PM.

  4. #4
    Senior Member skilsaw's Avatar
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    I'm confused here. You speak of shims and spacers, but from my understanding of how to set up a steerer tube, the shims and spacers are the same thing. Is that correct, or am I missing something.
    The one who has the most bikes wins.

  5. #5
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    Shim to go from 1" diamter steerer to 1 1/8" diameter stem


    Spacers to stack vertically between the headset and stem


    If I went with 1 1/8" spacers, I'd have to stack two of those shims vertically. (unless there is a really tall shim out there I haven't seen)

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    o i thought your shim had a lip on it. the way you said it in your first post will be fine once tightened

  7. #7
    coprolite fietsbob's Avatar
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    .. top cap in a threadless steerer presses down on the top edge of the stem,
    [so It must be 1.125" type]
    and the spacer rings beneath the stem, to do the headset pre load adjustment.

    Then you tighten the pinch bolts in the stem around the fork steerer to maintain that adjustment.
    if the fork steerer is a 1" type, then the shim tube makes up the difference
    between the 1 inch steerer OD and the 9/8 inch stem ID, it is 1/16th of an inch thick.
    so when wrapped around the 1" tube the new OD is 1.125"..

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    Almost all 1-1/8" stems come with a reducer bushing to let them fit a 1" steerer. So, add 1" spacers as needed, above the headset and below the stem, then add the stem with it's reducer above the spacers. The reducer will let the 1" spacers work properly. Use just enough spacers below the stem to let the steerer to project about 3 above the stem. Then, above the stem add a 5 mm 1" spacer and put the top cap on top of it.

  9. #9
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    Quote Originally Posted by fietsbob View Post
    .. top cap in a threadless steerer presses down on the top edge of the stem,
    [so It must be 1.125" type]
    No it doesn't have to be a 1-1/8" top cap if you use a 1" spacer ABOVE the stem.

  10. #10
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    Quote Originally Posted by fietsbob View Post
    1, .. top cap in a threadless steerer presses down on the top edge of the stem
    But isn't the 1" top cap pressing on the 1" shim that is pressing on the 1" spacers. Which can then be tightened in place with the stem pinch bolts. I'm not seeing why it wont work with the 1" bits. Someone explain to me why I'm an idiot and I'm going to die with the 1" bits.

  11. #11
    cab horn
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    Quote Originally Posted by luckett View Post
    But isn't the 1" top cap pressing on the 1" shim that is pressing on the 1" spacers. Which can then be tightened in place with the stem pinch bolts. I'm not seeing why it wont work with the 1" bits. Someone explain to me why I'm an idiot and I'm going to die with the 1" bits.
    Yes you're right.

    Your 1" top cap will press down on 1" spacers. You do not need 1 1/8 spacers.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  12. #12
    coprolite fietsbob's Avatar
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    If the shim tube is continuing the transfer of the compression of all the spacers exerted by tightening the bolt
    in the top cap, then all is good. the stem is gripping the shim and squeezing it ,
    which in turn is squeezing the slotted tube around the steerer tube ..
    a gap above the the top of the steerer tube to the stem top edge, is typically how 9/8" stuff is set up.

    insure that the gap cut in the shim is facing back so it gets squeezed by the stem, effectively.

  13. #13
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    Quote Originally Posted by fietsbob View Post
    ....a gap above the the top of the steerer tube to the stem top edge, is typically how 9/8" stuff is set up..
    It's also how 1" stuff is set up. But if the steerer is carbon, leaving the steerer long enough to require a spacer above the stem is a good idea and useful with any other steerer material too. In this case it will allow a 1" top cap to be used with a 1-1/8" stem.

  14. #14
    cab horn
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    Quote Originally Posted by HillRider View Post
    It's also how 1" stuff is set up. But if the steerer is carbon, leaving the steerer long enough to require a spacer above the stem is a good idea and useful with any other steerer material too. In this case it will allow a 1" top cap to be used with a 1-1/8" stem.
    He's heading for a darwin award with 85mm of exposed steerer on a 1" system anyways. 1" carbon systems tolerate much less spacers than 1 1/8.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  15. #15
    coprolite fietsbob's Avatar
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    You could make one .. access to a few machine tools,
    you could always use a single tube to serve as spacers and the shim.
    just need a slot, where the stem grips, so it can compress that portion,
    around the actual steerer tube..
    Last edited by fietsbob; 12-31-10 at 05:44 PM.

  16. #16
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    Quote Originally Posted by operator View Post
    He's heading for a darwin award with 85mm of exposed steerer on a 1" system anyways. 1" carbon systems tolerate much less spacers than 1 1/8.
    Yeah but I have to assume (hope?) the 85 mm includes about 40 mm for the stem? Even so, a 1" carbon steerer still won't tolerate the residual 45 mm of spacers but a steel steerer will. Most 1-1/8" carbon steerers would too.

  17. #17
    coprolite fietsbob's Avatar
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    Hopefully it will be sandy muddy course if it does break,
    then He will just go down in a soft goo.

    Is it carbon steerer Luckett ? I dont read you offering that detail,
    just others have suggested so ..

  18. #18
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    You guys seem to be enjoying the idea that it's carbon so much that I hate to bring you back to reality!

    It's a chunky AL steerer and I've been hammering on it for over ten years, so I don't expect to be doing any Hincapie impressions with it soon.

  19. #19
    cab horn
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    Quote Originally Posted by luckett View Post
    You guys seem to be enjoying the idea that it's carbon so much that I hate to bring you back to reality!

    It's a chunky AL steerer and I've been hammering on it for over ten years, so I don't expect to be doing any Hincapie impressions with it soon.
    That steerer broke because it was previously crashed. Not because it was weak.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  20. #20
    Senior member Dan Burkhart's Avatar
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    Quote Originally Posted by HillRider View Post
    Almost all 1-1/8" stems come with a reducer bushing.
    I sold numerous brands of stems and don't remember any being supplied with a shim, or reducer bushing. They are available separately of course.
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