Stuck top cap

[quixoticgeek]

Was trying to change the spacers round on my steerer tube so tried to undo the top cap. It doesn't budge. Just rotates and rotates, in either direction. Has anyone else experienced this, any ideas ?

[Brucey]

if you have used a standard star-fangled thingy,  and it is newish (so not corroded) it is possible that the threaded centre part of it is not crimped fully, and is spinning in the rest of it. The centre part sometimes loosens during installation if the thing is driven home using a bolt threaded into the centre, i.e. so that the load is not applied to the springy bits.

Suggestion; if you have access to an air impact wrench, or similar, try using that, whilst applying pressure from below (eg by holding the stem (with loose bolts) whilst bearing down on the bike).

If all else fails I would suggest cutting away one of the spacers with a hacksaw; this may then allow you to free the parts by some devious means.

cheers

[zigzag]

do you have a star fangled nut or a bung in your steerer? if the bung/nut rotates together with the bolt (meaning there is little friction with the inner wall of the steering tube), can the top cap just be lifted up with the help of a flat screw driver?

[quixoticgeek]

do you have a star fangled nut or a bung in your steerer? if the bung/nut rotates together with the bolt (meaning there is little friction with the inner wall of the steering tube), can the top cap just be lifted up with the help of a flat screw driver?

Star fangled nut. I don't know if the nut is rotating star and all, or if it's just the bit in the middle that's rotating. I'll try with a screw driver when next with the bike.

J

[Karla]

For a bit more oomph, try wedging the screwdriver underneath an edge of the cap or one of the spacers and hitting with a hammer.

[Brucey]

thinking about it, it may be possible to bring something (something long) to bear against the underside of the SFN via the base of the steerer, once the wheel and the mudguard are removed.

If you are going to try prying the top cap, it is probably best to start with the edge of a knife blade, or something equally thin.

cheers

[robgul]

thinking about it, it may be possible to bring something (something long) to bear against the underside of the SFN via the base of the steerer, once the wheel and the mudguard are removed.

If you are going to try prying the top cap, it is probably best to start with the edge of a knife blade, or something equally thin.

cheers

Poking up from the fork-crown (if it's hollow, and a caliper-type brake would have to be removed too) did strike me as a possibility to bash the star nut to bite, or even punch it right out of the steerer tube, cap and all.  BUT depends on frame/steerer material on how aggressive you can get

Rob

[quixoticgeek]

thinking about it, it may be possible to bring something (something long) to bear against the underside of the SFN via the base of the steerer, once the wheel and the mudguard are removed.

If you are going to try prying the top cap, it is probably best to start with the edge of a knife blade, or something equally thin.

cheers

Poking up from the fork-crown (if it's hollow, and a caliper-type brake would have to be removed too) did strike me as a possibility to bash the star nut to bite, or even punch it right out of the steerer tube, cap and all.  BUT depends on frame/steerer material on how aggressive you can get

Rob

It's a steel frame/fork.

J

[Ian H]

It may be possible simply to release the clamp bolts on the stem and heave upwards.

[quixoticgeek]

It may be possible simply to release the clamp bolts on the stem and heave upwards.

Tried that...

J

[quixoticgeek]

Gonna need a replacement before I try anything else. I need to keep the bike in a ridable state.

Any recommendations for alternatives to star FNaghatanlged nuts welcome.

J

[Brucey]

re the long rod from beneath idea; if the steerer  is steel 1-1/8", a 3/8" rod with a square end should miss the protruding end of the M6 bolt and bear against the centre part of the SFN.

Probably a little pressure on it will hold it well enough/detension the bolt enough to allow the M6 bolt to be removed. [Chopping one of the spacers out (as previously suggested) instead should also detension the bolt to similar effect.]

If you manage to release the bolt this way you will be left with a faulty SFN in position. This can be knocked down and left in situ, and (pending a better solution) a new SFN can be installed on top.

I suspect that the centre part of the SFN is spinning, because if the whole SFN is spinning, it would normally also have risen slightly with the treatment you have given it; (they normally slide before they rotate inside a steel steerer).

If you can get a suitable bolt and nut through a SFN, you can re-crimp the centre part. It may be possible to do this in situ with the SFN that is in there at present.

good luck!

cheers

[Karla]

Gonna need a replacement before I try anything else. I need to keep the bike in a ridable state.

Any recommendations for alternatives to star FNaghatanlged nuts welcome.

J

Just buy and install a new SFN? 

Brucey's idea sounds like the best one: remove the wheel, upend the bike and get physical on the SFN with a rod and hefty hammer.

[Paul]

Glue? Turn the bike upside down and apply some glue to the SFN in the hope that it binds the threaded centre part to the star part enough to be able to unscrew the bolt?

You might have to apply glue with a stick/spoke/other long thin thing.

Long nosed pliers? Could you get hold of the spinning bit while unscrewing the bolt?*

Rod? Just apply pressure to the end of the bolt with a rod from underneath, in the hope that it stops the threaded bit from spinning while unscrewing from above?*

(*You might need more than 2 hands for these attempts).

Good luck.

[Brucey]

Brucey's idea sounds like the best one: remove the wheel, upend the bike and get physical on the SFN with a rod and hefty hammer.

hang on, that wasn't quite what I was suggesting, although it is good method if all else fails....

cheers

[Paul]

Rod? Just apply pressure to the end of the bolt with a rod from underneath, in the hope that it stops the threaded bit from spinning while unscrewing from above?*

I've realised that my subconscious shamelessly stole this from Brucey's first reply and then pretended to me that it was my idea.

Soz

[mzjo]

Any chance a suitable socket and several lengths of extension tube could hold the nut still while the capscrew was undone in a conventional way? Depends on a lot of variables including having suitable extensions and 6 point socket (don't know the size off hand but the socket would need to be probably about 1mm bigger than normal, 9mm for a 5mm thread,11mm for a 6mm, but i think that they are 5mm), having not too much thread sticking through the nut, having the crimp holding the nut accessible etc. It would probaly require tapping the socket onto the crimp with a light hammer.

[quixoticgeek]

I bought a BBB Powerhead to replace the star fangled nut. In the end I chickened out of the removal of the nut, and took the bike to my LBS, where they drilled the bolt out, whacked the nut down into the steerer, and fitted the powerhead. Gives me some hope that if I need to adjust spacers and fettle the stem I can now do it on my own.

Thanks everyone for your suggestions

J