Expander plug won't stay put

[fignon's barber]

Working on a bike that seems to be baffling a LBS mechanic: carbon steerer tube with threadless headset and stem. He set it up 3 times, but the assembly loosens after 2 or 3 miles on the road. He didn't cut the steerer tube low enough atmo ( I've always used 2-3mm below top of stem clamp as long as you use expander bolt) but had 15mm of spacers above stem. I fooled around with it and noticed that the expander bolt kept turning when you adjusted the headset, never feeling tighter. when I removed it to see what was going on, I saw that the expander had pulled up. I snugged up the expander after pushing it back into the steerer (fairly tight). All seems good now.
Questions:
does anyone ever come across this?
does anyone use anything on the inside of the of the steerer to aid in the expander gripping?
Did I miss something?

[Cicli]

Working on a bike that seems to be baffling a LBS mechanic: carbon steerer tube with threadless headset and stem. He set it up 3 times, but the assembly loosens after 2 or 3 miles on the road. He didn't cut the steerer tube low enough atmo ( I've always used 2-3mm below top of stem clamp as long as you use expander bolt) but had 15mm of spacers above stem. I fooled around with it and noticed that the expander bolt kept turning when you adjusted the headset, never feeling tighter. when I removed it to see what was going on, I saw that the expander had pulled up. I snugged up the expander after pushing it back into the steerer (fairly tight). All seems good now.
Questions:
does anyone ever come across this?
does anyone use anything on the inside of the of the steerer to aid in the expander gripping?
Did I miss something?

I have greased the bolt and wedge on the expander and also added a bit of carbon paste for grip.

[ultraman6970]

DO you have a spacer under the stem??? It happened to me with an specific headset that I had to put a 1mm spacer under the stem just because after 30 mins the headset was getting a little play.

Sometimes what happens is that the headset top cap and the bottom of the stem are not straight or the top cap lokkes like flex a little bit and thats the reason you need to add a spacer between them to spread the load straight down how it should be.

Regarding the expander, some just dont cut it, you might need a new one too you know, If the thickness of the steering tube is tad thin and the expander wedge is at its limit the epxander wont work as intended. Well you could have a 1 inch expander in there too you know.

Which headset and stem are we talking about?

[ColonelJLloyd]

I always use carbon assembly paste on expanders. The Whisky one I just installed is holding well, but when I need to buy one I like ENVE.

[John H.]

I have seen this happen- especially with lighter forks (with lighter steerer tubes) like the Enve 1.0.
1st line of defense is making sure install is proper.
1.) Steerer cut flat so the top of the plug has full contact on top edge of steerer.
2.) (this is the major one)- install plug properly. Disassemble then grease the bolts and the beveled faces of the expander. Put back together. Wipe off grease if any will contact inner part of the steerer tube. Torque expander plug to 8NM.

If this does not work 100%-
1.) Try adding carbon paste to inside of steerer tube before inserting expander.
2.) Switch to a Specialized expander plug. There plug seems to be superior to most others.

[batman1425]

Working on a bike that seems to be baffling a LBS mechanic: carbon steerer tube with threadless headset and stem. He set it up 3 times, but the assembly loosens after 2 or 3 miles on the road. He didn't cut the steerer tube low enough atmo ( I've always used 2-3mm below top of stem clamp as long as you use expander bolt) but had 15mm of spacers above stem. ?

It isn't good practice to cut a steerer below the top of the stem clamp. Even with a good expander plug supporting the inside of the tube, this is a recipe for a cracked steerer tube/failure at a less than ideal time. You should have at least 5mm of tube above the top of the intended stem location with spacers to allow for setting the preload. In addition to reducing the risk of crushing the tube when tightening the clamp bolts, it will also give you wiggle room if you were to change to a stem with a taller clamp. I know lots of people what that pro look - but sudden front end failures are not worth the risk IMO.

Back to the original question - I had a expander plug with this problem and greasing the bolt while also apply a bit of carbon paste to the inside of the tube seemed to fix things. Make sure you don't get any paste on the outside of the tube where it could potentially contaminate the headset bearings. That's a fast way to ruin them.

[BdaGhisallo]

2.) Switch to a Specialized expander plug. There plug seems to be superior to most others.

I can second this option. Spec plugs are the best.

[El Chaba]

JB Weld the plug in place...

[johnniecakes]

JB Weld the plug in place...

Always my goto solution

[fignon's barber]

Thanks for the good advice, I think the carbon paste is the next step, followed by a specialized plug if it doesn't solve it. When I stuck my finger into the steerer tube, it was very smooth and had a white dust in it (not carbon saw dust from cutting steerer). And, yes, the thought of epoxy did cross my mind.

[djdj]

You probably know this already, but not all plugs are designed for the same size steerer. Check the inside dimension of your steerer and the specs of the plug. You shouldn't need carbon paste.

[tigoat]

Some good info has been provided so I have nothing more to add. With that said, I would toss that ENVE plug into a recycle bin in favor for something else better.

[Cicli]

Some good info has been provided so I have nothing more to add. With that said, I would toss that ENVE plug into a recycle bin in favor for something else better.

Agreed,
Every enve olug I have dealt with was nothing special. I like the ones that are about two inches long. That or the FSA plug that has the suported cap as well.

The Deda plug works nice.

[cadence90]

.
2.) Switch to a Specialized expander plug. There plug seems to be superior to most others.
Are the Specialized expanders still available?

I cannot find them anywhere.

[parallelfish]

The Deda plug works nice.

Yes, the long Deda plug.

Recently had the same issue - plug kept pulling out. The larger contact area of the Dada plug resolved the issue with very conservative torque values.

[shovelhd]

ITM makes a long one as well. Available through Ribble. I have one on my Redline, with a Paceline top cap, of course.

[fogrider]

the function of the plug is to apply pressure with the cap until the stem bolt(s) are tightened. I then back off the bolt on the cap just a little.

[El Chaba]

the function of the plug is to apply pressure with the cap until the stem bolt(s) are tightened. I then back off the bolt on the cap just a little.

I know this is true in theory, but in practice, if the expander plug is wimpy for whatever reason the headset will lose its preload and loosen in use.....especially in rough road conditions.

[topflightpro]

I had this happen to me. Carbon paste wasn't enough. I had to torque the crap out of it to get it to stay. I was not to happy about it, but it's held together fine.