Please advise me on what to do. While attempting to adjust my headset, the aforementioned nut appears to have lost its grip on the inside of the steerer tube. Now, I can neither undo the adjusting bolt, to remove it, nor tighten it to adjust the pre-load on the headset. Rotating the bolt on the top cap just spins the star inside the steerer tube.
What is the best way to remove the bolt, and then tighten the nut?

Many thanks.

Open steerer? Get something long and stiff (oo err missus)and shove it in from the bottom. You should be able to get some purchase on the SFN and try undoing it. After that possible drill the bolt head out and remove that way then hammer it down. The interesting question is why really and that will determine if you just use another SFN or try using a head doctor type device next.

Um.
If you can get a bit of weight on it you might be able to tighten it until if snaps. This may well still be possible even if it’s spinning while attempting to loosen it.
I accidentally pinged an alu bolt on a Hope top cap into a nondescript star nut while being stupid with bike in air on stand and fitting fork. It was obviously overtight but it’s not like it was a three foot lever and both hands or anything – just regular Allen key in hand. The bolt sheared and the starnut deformed/ top half mostly came off.
I own a torque wrench in bike sizes now as a result.
If you can over tighten and ping it, then knocking the remaining halves of starnut out and seating replacement should be trivial.
If not, how much clearance do you have and is it a metal steerer? If you can get an edge (big ship fixing screwdriver etc) under there then you should easily get enough wobble/leverage on to wreck the starnut. You could try slipping a hacksaw blade under maybe- once the top cap bolt is missing and you can lift the cap, the starnut is toast with a couple of hammer blows.
Just depends what materials you have really.
If it’s a carbon steerer I’d let someone who you trust do the work.
My opinion: if it has failed like this while setting up, starnut and bolt need replacing (about three quid for bits) hence I’m focussing on destructive methods.

Just reread and I’m wondering if you’ve already snapped the starnut (SFN).
It’s made of two halves (each kinda star-ish) with a little union between.
The top cap bolt goes into the union in the middle which has a thread for it.
The star bits are driven by force to wedge against the walls of the steerer (hence you thump them to get it out)
If the entire star is spinning you really have a problem as it must have cut channels inside the steerer to do this. Ad the starnut needs to be a specific distance down then that leaves Hed Doctors or new steerers as real solutions.
It’s far more likely that you’ve just broken the starnut though in which case any of the methods above (including thumping from below) or a combination are fine and you just need to replace nut and bolt.
If you’re really set on getting the bolt out, wedging something under the lip between the top cap and steerer may take up enough slack that you can carefully remove the bolt. Again, not if carbon is involved.

One you’ve got the bolt out then leave the star nut in and just hammer it a bit further down the steerer then simply fit a new star nut – job done.

If the nut hasn’t seized onto the bolt you may be able to tighten it all the way up and get it to pop out the top with a bit of leverage under the top cap. then install a new one.

Vincent how tight were you doing the bolt u? It’s only got to be finger tight, if that. You should never be even close to snapping it.

Knock it down, put another one in on top. 30 second job

Knock it down, put another one in on top. 30 second job

On some steerers you could knock the SFN right through and out of the bottom. This is increasingly rare though.

Another option is to get some long nosed pliers and bend the tabs up one at a time -they’re not that strong. Tricky if the bolt wont come out though.

If it’s that loose, then undo the stem and knock it up?

robarnold – Member
Knock it down, put another one in on top. 30 second job

End of thread

If you can’t get the bolt out and top cap off, you can’t knock it down.

[Edit] Okay, you could grind the top of the top cap off, or drill the bolt. [/Edit]

It sounds like the star nut is broken. You need a way to get it out of the top of the tube, as the top cap is still in place.

The steerer tube on the fork is most likely hollow. You need a long piece of metal, put it in the steerer tube at the bottom, and whack it with a hammer (wrap something around your stanchions in case of mishaps!!) to bend the claws of the star nut upwards. It will then come out of the top

If you don’t have the long metal object, it will likely cost nearly the same to buy one as to get your LBS to do it for you. It isn’t a long job.

Many thanks for all the advice.
I used an implement inserted up me tube to tap the pesky nut to a new position inside the steerer, where it had not scored grooves into the wall. I was then able to undo the bolt. The star had enough grip in its new spot to properly adjust the headset. Result: disaster averted! I am off now for a South Downs epic.

I think I will replace it later a Head Doctor tho, just in case.

It’s pretty blowy up top but fairly dry – enjoy 🙂

HOPE Hed Doktor, (whatever…) Job Done, NEXT!