My daughter's bike has a threaded headset, and I don't know what tool I need to adjust it. As you can see from the picture, there are the following parts in the stack:

  • a knurled ring, which presumably isn't very tool-friendly
  • a ring (with a diameter of 35 or 36 mm) with three notches spaced equally apart (I'm not sure whether or not this is permanently attached to the knurled ring)
  • a standard six-sided nut, which I assume I can loosen and tighten with an ordinary crescent wrench

It looks like I'll need some sort of special tool for the ring with the three notches. What tool will I need for adjusting this headset?


  • I might be wrong but the ring with 3 notches might be just a spacer (not threaded). It that is the case you would need to tighten knurled ring, then six sided nut, and then tighten them against each other Commented Jun 18, 2013 at 7:01
  • In the absence of the "Correct tools", I have used plumbers pipe dogs (pipe wrench?) in the past. The large nut needs a pretty large spanner, and as is typically the case, my largest adjustable opens to 1mm too small....
    – mattnz
    Commented Jun 18, 2013 at 7:07
  • Do note that if what you want to do is adjust stem height/angle that's done with the bolt at the top of the stem. And I agree with Davonin that the notched flat thing is probably just a washer, with no threads. You use the knurled nut below it to adjust the bearings, after loosening the top nut. The notches are probably used to prevent the washer from turning (and indirectly turning the knurled nut) while tightening the top nut, but firmly holding the knurled nut will serve the same purpose. Commented Jul 3, 2013 at 15:11
  • @DanielRHicks I made the adjustments a couple of days ago, and the notched flat thing is threaded (it's not a washer).
    – amcnabb
    Commented Jul 4, 2013 at 15:06
  • In that case it's just another lock nut. Commented Jul 4, 2013 at 16:23

2 Answers 2


The bottom ring is used to provide tension against the bearings to stop the headset from wobbling around. It only needs to be hand tight, hence no spanner/tool attachments.

The middle and top ring are tightened against each other, as a lock ring to prevent the bottom ring from loosening.

The top ring can be tightened with any spanner of the right size.

The middle ring requires a specialised spanner called a C-Spanner, a hook wrench or a hook spanner. It looks like the image below and is readily available from any bike shop or online store. Eg: Chain reaction sells one from Park tools

enter image description here

  • Instead of using special tool for the middle ring you can use simple hammer and chisel (of course use it gently).
    – J-unior
    Commented Jun 18, 2013 at 7:47
  • Thanks - I now know what that gadget in my toolbox is for :)
    – mattnz
    Commented Jun 18, 2013 at 8:50
  • A quick search isn't revealing products called "C spanner", but I'm seeing a bunch of tools online that look similar to this with names like "lock ring spanner", "shock spanner wrench", "lock ring wrench", and "adjustable pin spanner wrench". Are any of these the same as a C spanner? Are there different sizes of C spanners, or is there just one size?
    – amcnabb
    Commented Jun 18, 2013 at 15:35
  • @amcnabb I've updated with some more detail about the hook wrench. The pin spanner is slightly different from what you need.
    – Mac
    Commented Jun 19, 2013 at 0:03
  • Thanks for the update. Do spanners work on a wide range of diameters? It looks like bottom brackets are usually around 45mm, but the headset is around 35mm.
    – amcnabb
    Commented Jun 19, 2013 at 2:55

All you need, is a large adjustable spanner that expands 30 plus mm, and large Channel Locks.

Usually I can take the loose headset adjustment cup(that knurled flange) and snug it up so you feel bearings get bumpy tight, just moderately tight or "binding" then snug up the top locknut with adjustable only maybe 1/4 to half turn after you feel it start to bind on the lower cup just mentioned.

Now you can take Channel Lock wrench and REVERSE or back turn it INTO the top locknut with you holding top nut fixed with the adjustable, it will tighten into locknut very well AND back off on bearing tightness so that fork turns fairly free, but with no bearing play at all.If end result still feels tight, then back off only SLIGHTLY on top nut so that you can also back the knurled ring adjustment bearing cup AGAIN, into the top nut, reducing the tightness affect yet still providing a free rotation of fork with no play.

If you take stem off, you can then get a sensitive feel for bearing smoothness. You really want it just slightly tight or "bumpy" so that fork can wear in, without working head bearings loose with the dreaded bearing play, that makes bike handle horrible and wear out bearings or even crack them. Loose headset also makes bike ride horrible too Too tight is no good as well, so keep a good feel for how tight or free the headset steerer tube bearings are.

Once locked down the bike will ride nice and keep lil rider happy and in best bike control. Good luck.

Last thought, I see the slotted lockring that can make things more complicated at first, if you have that maybe you better let a competent shop adjust bike headset and while at it make sure whole bike is mechanically sound and lube the chain.

Your lil rider with limited strength in legs will appreciated the solid bike with less drag.

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