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Cant remove top stem bolt? Need advice

gt8374uh9jiodpogt8374uh9jiodpo Posts: 51
edited June 2019 in Workshop
Hi

Trying to remove the stem to swap for a different size and I cant remove the 5mm allen bolt.

It loosens but it loosens with the centre cap attached to it, and when seems to be fully loose they dont come out all the way because the gubbins inside the stem are still attached. They perhaps lift up a 1.5cms but are still attached. I have re tightened and put the handlebars back on for now, but does anybody know how I can get the bolt to come away from the cap?
I have tried gripping the cap with rubber gloves but the two seem like they are bonded together. Also tried loosening off the two bolts on the side of the stem but didnt work either.

My local bike shop gets booked up months in advance this time of year so would like to resolve this myself of possible.

Posts

  • keef66keef66 Posts: 13,123
    So can you unscrew it all the way and remove it with the cap attached?

    If so, do that, swap stems, and screw it back on?

    Or am I missing something??
  • No, when I lift them up they are still attached to the inners.

    Sorry missed that part. Just added to post above.
  • Ah rats, now its off but the bottom (wedge?) bolt has dropped into the stem tube. How would I get that out re attach?

    What a day.
  • Ah rats, now its off but the bottom (wedge?) bolt has dropped into the stem tube. How would I get that out re attach?

    What a day.

    Turn it upside down?
  • keef66keef66 Posts: 13,123
    Either invert the bike or drop the fork out and invert that.
    Maybe it's time for a new bung and top-cap? Then you can choose a different design that won't fall apart.

    My Scott has one which tightens in the steerer using a 6mm allen key then the top cap bolt goes in and is tightened using a 5. So undoing the top cap has no effect on the bung which remains firmly located in the steerer.
  • Right. Stem swapped and in position. I now have a wedge bolt (which is wider at one end) and a metal cylinder left on the table, a sort of metal cup and washer, plus of course the stem screw.
    Anybody kind enough to clarify what i do next. In simple terms as i am a total noob (as you can tell)
    Worried about dropping the bolt in again.
  • mugensimugensi Posts: 559
    Right. Stem swapped and in position. I now have a wedge bolt (which is wider at one end) and a metal cylinder left on the table, a sort of metal cup and washer, plus of course the stem screw.
    Anybody kind enough to clarify what i do next. In simple terms as i am a total noob (as you can tell)
    Worried about dropping the bolt in again.

    Post a picture of it as it'll be easier to explain how to put it back together
  • ok think I have worked it out through logic.
    the smaller diameter end of the bolt goes into the cylinder. Put in the screw from the other end of the cylinder and when it threads the bolt it will expand the cylinder as it draws the bolt inside. Thus creating outward force from the cylinder to the stem insides thus clamping it.
    The cylinder is called a shim it transpires.
    If that makes sense?
    Not signed up to any photo sharing websites so cant get a photo up right now.
  • keef66keef66 Posts: 13,123
    Yes, that makes sense. Just make sure you install it at the right point in the steerer.
  • AlejandrosdogAlejandrosdog Posts: 1,975
    dont forget the wot not with widget torque
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