carbon steerer expander plug

[fignon's barber]

Originally Posted by AngryScientist

damnit; frustrated.

my new-to-me swisscross came with a kcnc expander plug for the steerer.

the way this one works is you use a 4mm hex to tighten the expander (counter clockwise) into the steerer tube, and then the 5mm hex bolt preloads the top cap (clockwise tighten).

i've tried everything i can think of to keep the expander tight when i tighten the top cap. even used blue locktite overnight on it.

no dice.

after some harsh gravel this weekend, and my top cap rattling loose every couple hours, i'm ready to throw this thing in the bin.

any advice or should i get a different, better expander?

It has been my experience that if the expander won't hold, it's not the expander that is the root cause. It's either an issue with the headset (possibly doesn't fit ht cup size) or maybe you need a small 5mm spacer between cap and stem.

[AngryScientist]

to expand a bit: my problem is not that the expander is slipping; the problem is that when i tighten the top cap bolt (clockwise) it loosens the expander loading bolt (which is reverse threaded).

i ordered one of the spec ones, but in the mean time, i put even more locktite on that bolt and will let it sit overnight before installing the top cap.

i already have the headset preloaded fine, and the stem is keeping everything tight, it's just that the top cap bolt keeps coming loose on really rough road surfaces.

[cribbit]

Why is the expander bolt reverse threaded?

I have cheapo chinese ones that work great.

Also @ the long expander - I thought these are supposed to seat at the edge of the steer tube no matter what, with the same diameter as the tube? It would go inside of any spacers.

[skiezo]

I have been using these on my road bikes and really like them. I can take it in and out without any damage to the carbon steer tube. Not sure how it would work on a gravel ride.
https://fairwheelbikes.com/tune-gum-gum-expander-plug/

[pdmtong]

Originally Posted by donevwil

Best expander bar none is from Specialized, appears they are still available. Replaced the POS Enve expander than came in a 2.0.

Originally Posted by AngryScientist

that's good enough for me!
@ 10 bucks, i'm just ordering one.
thankss!

you guys know AMain is the reincarnation of Performance and Nashbar...
https://www.bicycling.com/news/a2630...cycle-closing/

[JeffWarner]

Originally Posted by Dino Suegiù

It really isn't so difficult at all.

Here is a good quick video:

https://www.youtube.com/watch?v=YNizysonc74



The best I have used are Deda, Colnago, Specialized; the worst ENVE and tune.

Nice trick! Thanks for the video link.

I do the first part (loosen the bolt and tap) to get the ENVE expander lose, but leveraging out the top with a tool is something new.



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[pdmtong]

Originally Posted by JeffWarner

Nice trick! Thanks for the video link.
I do the first part (loosen the bolt and tap) to get the ENVE expander lose, but leveraging out the top with a tool is something new.
Sent from my iPhone using Tapatalk

agreed thanks for the video!

[Dave]

Fsa expanding plugs work OK, but after I get the steering tube length right, I epoxy glue in a 1 inch star nut and never have to bother with one again.

[El Chaba]

You need to know the proper stem height, but I generally use JB weld to secure the plug. You need to install a "dummy" bolt with a bit of grease on it to keep the adjustment plug threads clear, but a layer on top of the plug keeps things in place forever. I have fixed at least a dozen cases of headsets repeatedly coming loose for friends. The recidivism rate is zero.

[jc031699]

Adding this to the archive




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[Gummee]

Talked to the local SBC dealer. They told me $20 for that expander.

Despite working in another shop, that $10 wedge from amain is still a great deal

M

[AngryScientist]

yup.

to close the loop on my own thread, i got that specialized one. it is 1000x better than what i started with. perfect. zero problems now. satisfied customer.

[m_sasso]

Originally Posted by skiezo

I have been using these on my road bikes and really like them. I can take it in and out without any damage to the carbon steer tube. Not sure how it would work on a gravel ride.
https://fairwheelbikes.com/tune-gum-gum-expander-plug/

Originally Posted by Dave

Fsa expanding plugs work OK, but after I get the steering tube length right, I epoxy glue in a 1 inch star nut and never have to bother with one again.

A proper carbon steerer compression plug needs to provide two functions

1.) Provide compression for the head set stack.
2.) Provide support to the diameter of the carbon steerer tube being clamp compression loaded through the steering stem.

Those small surface area, any thing less than 40+mm in height compression plugs and star nut plugs satisfy function 1.) Provide compression for the head set stack, perfectly however fail miserably at function 2.) Provide support to the diameter of the carbon steerer tube being clamp compression loaded through the steering stem.

If you use one better have a real good helmet, an outstanding dental plan and familiarity with a good facial plastic surgeon, they are dangerous, and consumer protection should outlaw them for ignorant peoples protection. Hit a bump hard and your stem crushes your unsupported carbon steerer tube and you will hit the pavement before you even know what was happening.

Don't take my comments seriously here watch this, https://www.youtube.com/watch?v=8bSnbjHiFXc

[tigoat]

This new version of Specialized plug is not as good the old one. The old one did not have those teeth on the top and you could pull it out without removing the bolt completely. To remove the old version, just loosen the bolt and give it a light tap to knock the plug down and then pull the whole unit out. I have a box full of them that will last me a lifetime.

[YesNdeed]

I had to look into expander plugs and their various designs a few years ago. After building up a F/F/HS I bought from a friend, the HS just wouldn't stay tight. I'm super happy I didn't die during that time. Unlike Angry's problem, the expander plug was in fact slipping. I think I replaced it with an FSA, but don't really remember. The rough surface area that came in contact with the inside of the steerer tube was way too smooth, and a new one fixed the problem for about $15. It was a nice relief to take the mystery out of what's going on in there.