I refurbished my bike and in the process got a new shiny quill stem to replace the original threadless stem. Unfortunately, like a dunce I forgot to ensure that the diameter of the stem adapter (the big bolt that connects the stem with the fork) fits the diameter of the fork. The quill stem adapter is ever so slightly larger in diameter than the fork.

I really want to keep both the brand new stem and the fork. Is there anything I can do to make them fit? Some sort of adapter to fit in between? Maybe a thinner bolt that fits the fork and the quill stem - and then somehow add "filling" between the new bolt and the stem? Open to any ideas.


It looks like I'm SOL. But in case this helps, here's the current threadless headset and the new quill stem I'd like to mount on somehow.

enter image description here enter image description here

  • There are some terminology mixups going on here. The stem you're replacing is threadless? Are you replacing a threadless stem mounted on a quill stem adapter with just a normal quill stem? What is the bike, what is the old stem, and what is the new stem? Commented Aug 4, 2016 at 23:31
  • I have seen adapters to convert a quill stem to a thread less system, but not the other way around (as requested by the OP). Given the way a thread less headset is tensioned it incompatible with a quill stem and your request is not currently possible.
    – Rider_X
    Commented Aug 4, 2016 at 23:41
  • Return it, buy the right size. Learn your lesson about measuring before ordering. Sorry, but the sooner you do this the more likely the shop is to accept it, especially if you buy the right size there.
    – Criggie
    Commented Aug 5, 2016 at 2:25
  • Is that a stem extender? If so, try removing it and see if the quill goes into the steerer tube proper. You might find it does, and the product suggested below will work. Albeit you may end up wanting a longer version of the quill stem.
    – Nuі
    Commented Aug 5, 2016 at 23:57
  • Replace headset with threadless one that takes quill stems and fits the head tube.
    – Kaz
    Commented Aug 9, 2016 at 3:57

1 Answer 1


There are products that do this, but they rely on the quill fitting inside the steerer.

enter image description here

You can also get threadless clamps that allow you to run a fork with no stem, and effectively DIY that product. They're mostly used by recumbent bikes that have a second pivot holding the handlebars, rather than by people not using handlebars at all.

enter image description here

If you're lucky you might be able to find a different quill stem that will fit inside your steerer tube. But then you have an aluminium steerer being pushed on by a steel quill in a way that the designer never thought about. That's why the commercial product clamps the quill rather than using the wedge bolt it was designed for.

But since the quill won't go into the fork steerer tube, that's never going to work. Milling out the inside the of the steerer tube, even a small amount, is risky. It's one of those "probably ok, but if it's not your face hits the road" things.

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