Headset to cap?

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  • June 15, 2015 at 11:04 pm #1032158
    hozn
    Participant

    To be clear, those two items pictured are for two different applications: one of those is a star nut for an alloy steerer (the top one) and the other is a carbon steerer compression plug. I hope you didn’t use the star nut in a carbon steerer …

    Yes, the top cap bolt pulls / compresses the headset pieces together so that when you tighten down your stem bolts everything is tight (and your steerer doesn’t shift around when you brake, etc.).

    June 15, 2015 at 11:04 pm #1032159
    jabberwocky
    Participant

    It pulls the entire assemble together (headset/stem/spacers) so there is no play. The stem actually holds it together once clamped. The bottom one looks like the carbon steerer versions I’ve seen, whereas you wouldnt want to use a star nut (top) on a carbon steerer.

    June 15, 2015 at 11:20 pm #1032161
    trailrunner
    Participant

    For metal steer tubes with a star-fangled nut (the parts in the top part of your photo) – Once you preload the bearings and tighten the stem to the steer tube, you can, in theory, remove the stem cap and bolt. However, I’ve never seen anyone do this.

    (Note that in your photo, the star-fangled nut is upside down relative to the green stem cap.)

    Also – as others have noted – you have two different systems shown in your photo. Don’t mix the parts between these two.

    June 15, 2015 at 11:22 pm #1032162
    TwoWheelsDC
    Participant

    Also, the star nut (top) goes the other way. The “stars” should be curving up toward the top cap.

    June 15, 2015 at 11:37 pm #1032163
    Jason B
    Participant

    @hozn 118136 wrote:

    To be clear, those two items pictured are for two different applications: one of those is a star nut for an alloy steerer (the top one) and the other is a carbon steerer compression plug. I hope you didn’t use the star nut in a carbon steerer …

    Yes, the top cap bolt pulls / compresses the headset pieces together so that when you tighten down your stem bolts everything is tight (and your steerer doesn’t shift around when you brake, etc.).

    No, it was on my Soma, which is why I asked. Seemed a little weird on a steel bike.

    And, no haven’t done anything yet. I just pulled it out and said, “hmmmm”.
    But honestly, tightening down the stem is not enough to secure everything? So if it is steel, the compression nut was overkill, or probably what was lying around?
    Thanks

    June 15, 2015 at 11:39 pm #1032164
    hozn
    Participant

    Yes, you definitely need the compression plug / star nut to remove the play.

    June 15, 2015 at 11:57 pm #1032168
    Jason B
    Participant

    @hozn 118142 wrote:

    Yes, you definitely need the compression plug / star nut to remove the play.

    Just thought I read somewhere it was a meh, cosmetic part, but wasn’t sure. Good to know. Didn’t know carbon and steel use different kinds. Always just transferred stuff from one bike to the next, never really comparing. Well, today I learned.
    Thanks for help fellas.
    Btw, put it on, it is way prettier, I think I may actually go faster.

    June 16, 2015 at 12:07 am #1032169
    trailrunner
    Participant

    @Jason B 118146 wrote:

    Just thought I read somewhere it was a meh, cosmetic part, but wasn’t sure.

    The stem cap (the green part) is cosmetic after you preload the bearings and install the stem.

    The star-fangled nut (the piece that looks like a star with the two ridges of black things) gets pounded into the inside of steer tube (although it is backwards in your photo). When you tighten the bolt on the stem cap, it draws the star-fangled nut and steer tube up into the head tube, which seats the headset bearings into the cups (this is a general description, and there are some minor differences in headsets, but this applies generally to all Aheadsets).

    Then you clamp the stem onto the steer tube, and tighten the bolts on the stem. At this point, you do not absolutely need the stem cap. You could unscrew the bolt and take the cap off if you want, and it should all stay together.

    June 16, 2015 at 12:50 am #1032172
    peterw_diy
    Participant

    +1 on trailrunner’s post. Once the stem is tightened the cap is not needed. But good luck if you ever need to adjust the headset and don’t have it.
    http://newsite.parktool.com/blog/repair-help/threadless-headset-service

    BTW if you want to try different stem heights you can buy “locking spacers” that can maintain tension when you take the stem off. Of course you always want a properly tightened stem if you’re actually riding.

    June 16, 2015 at 1:23 am #1032175
    Vicegrip
    Participant

    As said not needed mechanically once the bearings are preloaded and the stem right. That said I would hate to break a chain or the like and face plant an open steerer tube

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